March 2009 - The Arboretum
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Mulching vs. Lawns at the Arboretum

written by Francis ChingLasca Leaves 20:37, 1970For many years mulching practices at the Arboretum were carried on only to a limited extent. One reason was that since the Arboretum is adjacent to the Santa Anita Race Track, a great number of residents in the immediate area have always been conscious of flies and have related any kind of mulching and composting with fly infestation. Many times in the past, the Arboretum has been able to obtain manure as well as bedding material from race tracks, yet, despite thorough inspections by the County Health Department, the fly problem has been erroneously blamed on the Arboretum.Another reason why mulching practices have been resisted is that it was thought the general public would not appreciate large mulched areas as compared to a well-manicured lawn.Further, there was the question of salts and possible damage to plants from an accumulation of salts from manures. In the final analysis, it was determined that if manure were properly used as a mulch, salts, if present in even damaging proportions, would be leached away before being able to cause any damage.A fear that slopes heavily mulched would be subject to severe erosion from heavy rains or irrigation practices was thoroughly discounted by a timely demonstration. Although mulching to any extent had not been practiced since the Arboretum was started in 1949, and plants apparently grew “all right,” serious consideration was given in 1964 to a review of its advantages. lt was well known that in the early days of development, whatever topsoil there was, was scooped up, pushed around and eventually lost. Not only were there hardpans present in many areas but surface layers were also compacted due to heavy equipment causing poor aeration and an intolerable condition for adequate infiltration and percolation of moisture. It was glaringly noticeable following heavy winds in 1962, 1963, and 1964 that many trees were lost due to uprooting. All of these uprooted trees possessed a very shallow root system which made them prime candidates for “pushovers.” In addition, during digging and moving operations of large trees, many of the plants also had a very shallow root system which made moving operations quite difficult.Realizing the poor soil conditions, checks were made on actual moisture penetration. Even after a relatively heavy rainstorm of two inches in twenty-four hours, moisture penetration amounted to as little as two inches in some areas. Checks made after leaving rainbirds on for seven hours showed that moisture penetration was less than four inches.Poor Root Systems coupled with poor soil moisture penetration brought the sudden realization that irrigation practices were insufficient. This situation was worsened by the fact that it had always been more important to irrigate according to the needs of the lawn, taking it for granted that the trees and shrubs were receiving adequate amounts of moisture.Maintenance of a lawn in a heavily planted area poses many problems besides watering. Having to mow regularly between plants subjects plants to possible damage. On the other hand, if lawns are not adequately mowed, the area takes on an unkempt appearance. In order to keep all lawn areas mowed during the spring, summer, and fall months, six men were assigned to the task. This did not include the great amount of time necessary for servicing and repairing the equipment.Besides mowing, it was also necessary to spend endless hours in hand trimming grass away from the base of trees and shrubs. When this is not done regularly during the summer months, Bermuda grass has a tendency to climb up into the low branches of shrubs and up the sides of tree trunks.(This is the first part of a two-part article)

Staghorn Fern Culture

Your Aunt Etta left you her mammoth staghorn fern. It took three of your friends and a pickup truck to get it to your patio. It seems that being a dutiful nephew is now requiring you to ascend to levels of horticultural science that you would rather not traverse. All is not lost. The following is a short overview of staghorn fern culture that will help you preserve both the memory of your wonderful aunt, and the fern.
Staghorn ferns belong to the genus Platycerium and are native to tropical regions of Africa, Southeast Asia and Australia, where they grow on trees as epiphytes. There are perhaps 18 different species in the genus. The most common species grown in Southern California is P. bifurcatum, which will withstand temperatures as low as 20-22° [ degrees ] with only a lath structure for shelter. Several other species such as P. superbum, P. hillii, P. willinchii and P. stemaria are available from specialty nurseries. These species require greater protection from frost. Most of the remaining species require greenhouse cultivation.
Two Types of Leaves
Staghorn ferns produce two types of leaves or fronds. The sterile fronds are persistent, flat, and pale green, aging to tan and brown. They support the plant, enclosing the massed roots, rhizome and humus. Fertile fronds are deciduous, erect to arching or pendent and are divided into a few or many deep lobes. Due to the division, the fertile fronds resemble deer antlers. On the lower surface of the fertile fronds brown patches of spores form. The number and placement of the spore patches is distinctive for each species.
Potting or Mounting
The Staghorn ferns perform best mounted on bark, wood slabs, or slatted wood frames, furnished with moss and attached to the mount with either wire or nylon fishing line. They can also be grown on tree fern stem or, in the case of clumping species, in hanging baskets. Established plants will envelop whatever they are mounted on. All rely on atmospheric moisture rather than water directly at the roots. Daily spraying of the fronds during warm weather is beneficial with water being applied moderately to the roots. Fertilization is best applied as a monthly foliar spray on actively growing plants. Staghorn ferns grow best is bright shade or early morning sun , and will burn if given too much exposure to summer sun.
Propagation of clumping species can be performed by division of larger offsets in the spring. The rhizome is buried beneath layers of many dead, closely packed, sterile fronds. Cut through the layers of sterile fronds until the rhizome is severed and then mount it on a fresh support. Species which do not branch can only be propagated from spores.
The most common pests of Staghorn ferns are armored scale insects. Armored scale insects live their entire adult stage attached to one spot on the host plant. They have a waxy shell-like covering that protects them from natural enemies and insecticides. If the infestation is light they can be picked off rather easily. When a valuable plant is heavily infested you can clean off all the stationary adults and then spray with broad spectrum insecticide to control the crawling juvenile stage (first test the insecticide on your fern by mixing a small amount and then applying it to a small, inconspicous area of your fern).
Common Staghorn Fern
The common Staghorn fern is P. bifurcatum. The sterile fronds are up to 24 inches wide by 18 inches long. They are papery, erect, rounded to heart- or kidney-shaped, and shallowly or irregularly lobed on the upper margin. Fertile fronds are leathery and grow up to 3 feet in length. They can be erect, spreading, or pendent, and are 2 or 3 (occasionally to 5) times dichotomously forked. Their growth habit is clumping, producing new plants as the rhizome branches. There are a number of named cultivars such as 'San Diego', which has longer fertile fronds that are darker green. Platycerium bifurcatum is native to Southeast Asia, Polynesia, and subtropical Australia.

Out of Our Past

Thirty years ago there was a fire in the historical area. To quote a photo caption in Lasca (Los Angeles State and County Arboretum) Leaves, May 1973, “On December 26, 1969, a fire swept by 70-mile-per-hour winds cut through the center of the Arboretum producing scenes like these in the vicinity of the Queen Anne Cottage which, fortunately, escaped with only blistered paint.” The trunks of Washingtonia robusta palms in the area still show scars from the fire.Did you know that the Arboretum once had its own TV program? “Green Leaves,” a series of 13 half-hour programs, appeared on KNBC at 11:30 on Sunday mornings in 1968-69.At about the same time, a national search was on for Camptotheca acuminata, an uncommon tree from China. The Arboretum had a specimen donated by Arcadian Willard Hagen, as well as a second tree propagated from the first. The original tree was sacrificed to medical science so that an extract, camptothecin, could be evaluated as a cancer treatment.

Growing Notes: The White Jacaranda

George H. SpaldingLasca Leaves 18:41, 1968.To the true plantsman few experiences can match the thrill of seeing the first seedlings of a new and unknown plant obtained from some distant part of the world. It requires patience to grow a plant to maturity and give it adequate testing. There is always the temptation to introduce a promising species quickly while initial enthusiasm is high, without waiting for it to reach maturity, or go through a cold winter, or undergo any one of the many other tests required before a plant can be considered ready for introduction.When a plant has been fully tested and is ready for introduction, propagating stock plants are grown and made available to nurseries at cost of production. Although brief resumes are sent to trade journals when a new plant is released, to date no full account of Arboretum introductions has been published. So from time to time detailed reports of Arboretum plant introductions will appear in Growing Notes to provide a continuing official record.One of the most interesting LASCA plant introductions is the so-called white jacaranda. This selection is considered a pure white form of acutifolia; however, such an albino variation has not been recorded in the Peruvian floristic literature. This accession, received in 1952, resulted from the efforts of Dr. Russell J. Seibert, then director of the Arboretum. While working in Peru in 1946 he had seen trees of this white form growing at the Agricultural Experiment Station of La Molina in Lima. It was reported at that time to have been introduced into cultivation from wild material found near Huanuco, Peru.Feeling that this tree had great horticultural potential for Southern California, a successful attempt to obtain budwood was made resulting in the 1952 accession. Eleven dormant sticks were received. It has been reported that this jacaranda had been propagated by cuttings in Peru. The budwood sticks received were of thick caliper and failed to root when treated as cuttings. As soon as it became evident that the cutting method was not going to work, buds were taken and worked onto available rootstock of the typical Jacaranda acutifolia. Two of the budded seedlings “took,” but only one survived. This survivor provided buds for additional propagations two years later.The original tree at the Arboretum first bloomed in 1957. Its flowers appeared in rather small trusses in this first season, but the color was a good clear white. Flowerings in later years have produced larger trusses, but while occasionally promising, the over-all performance is disappointing. Consequently, bloom has been erratic and not particularly effective. We do not know the reason for this poor performance, but believe it to be physiological in nature, or possibly poor adaptation to this particular region. If the cause can be found and removed, the white jacaranda will become a major addition to our list of outstanding flowering trees.This jacaranda was offered to the trade through a notice in the Pacific Coast Nurseryman of April 1961 (Vol. 20, No. 4, pp. 20-21).Thanks are due Austin Griffiths, Herbarium Curator at the Arboretum, for the suggestion that this series be undertaken.

Some Outstanding Shade Trees for Southern California

George H. Spalding
Lasca Leaves 21:64-70, 1971

Southern California gardeners are fortunate in having a wide variety of trees available to them. Making a choice in this situation is sometimes difficult. Aside from such horticultural considerations as location, soil, and exposure there is the attitude of the person making the selection, perhaps the most important consideration of all.

None of the trees are perfect, if perfect means being in flower year round and never dropping leaves. Nonetheless, there are a number which, though falling short of this ideal, have, by reason of their adaptability, great value as shade trees. Those discussed in this article are outstanding in this respect.

Podocarpus [now Afrocarpus] gracilior Fern Pine

This beautiful native of Africa is one of the most outstanding shade trees for a wide range of situations. Often sold in nurseries as Podocarpus elatior, it has been grown in Southern California at least for 40-50 years. It is one of the cleanest trees in that leaf drop is no problem as the leaves are so small and needle-like. lt is free of insect pests and disease. In other words, it comes close to being the ideal shade tree for all areas in which it can be grown. Its major drawback, if it can be called one, is that it takes so long to reach its mature growth of 50-70 feet and a width of 20-30 feet.

Seedling-grown plants are quite upright. Cutting grown or grafted plants tend to be rather supple and floppy. They are fine for espaliers because of their tendency to make horizontal growth. They are often used as a substitute for vines along a fence or arbor. Both types make outstanding evergreen hedges, especially when clipped.

As a mature tree it has a billowy outline which is soft and pleasing. The shade is quite dense.

It would be very easy to say that this is one of the best all-around trees in existence. Ideal for street or patio tise and also excellent for container use when young. Very tolerant of a variety of soils, it can be grown over a wide area.

Schinus terebinthifolius Brazilian Pepper

A native of Brazil, Schinus terebinthifolius is another fine, small shade tree for patio or garden. It is one of the best for use as a lawn tree since it thrives on the type of watering program usually given lawns in this area. It heads too low for street use where 14 feet is often required height for the lowest branches.

This species of Schinus is much heavier and more densely foliaged than Schinus molle, the long grown and beautiful California Pepper. The leaves are dark green, somewhat shiny, and evergreen. The inconspicuous flowers are followed by scarlet berries. A certain amount of pruning is necessary to develop an open crown and overcome a tendency to cross branching and heavy growth. The ultimate height will be about 25 feet. One caution should he noted—during the past year or two there has been some evidence of damage and occasionally outright killing of trees by verticillium wilt. The best control is to watch the watering and feed regularly. In spite of this it is one of the best shade trees for this area.

Melia azedarach cv. umbraculifera Texas Umbrella Tree

The Texas Umbrella Tree is practically indispensable for those hot desert areas where very few trees will grow. It is a fast-growing tree which tolerates a wide variety of soil and growing conditions. The foliage is bright green and the leaves are bipinnately compound. In spring the tree is covered with fragrant clusters of small lavender flowers that are followed in the fall by yellow fruits often used for beads. Under garden or lawn conditions it will be a messy tree and will tend to send up suckers because of garden waterings. lt is not good near the coast nor in areas of heavy winds as the brittle branches tend to break. But in the hotter desert areas of southern California where it has been widely planted, the Texas Umbrella Tree is very effective, and those who have enjoyed its shade on a hot summer day in the desert will he ever grateful for it.

Koelreuteria integrifoliola (no common name)

A small, deciduous tree from China which seldom attains a height of more than 30 feet. The large leaves are bipinnate. The leaflets ovate-oblong about 4 inches long. The entire leaf often reaches 14 inches in length. Flowers are small but produced in large terminal panicles in summer when flowering trees are at a premium. The fruit which follows is bladderlike, somewhat resembling inverted Japanese lanterns. They are green at first turning a beautiful salmon pink with age.

This is the smallest of the genus, all of which arc worthwhile ornamental trees. Koelreuteria integrifoliola is well suited to the small city lot and will stand temperatures as low as 20°F, probably lower. In this area it self sows readily and seedlings are easily transplanted. We still do not know the full potential of this tree as it was introduced in the Los Angeles State and County Arboretum in 1958. The oldest tree there is only 19 years old and until its recent removal to a new location, requiring heavy pruning, was rather broad topped and rather attractive. Like the rest of the genus it is free of disease and insect pests.

Magnolia grandiflora Magnolia

Perhaps of the best known of the large evergreen shade trees in Southern California is Magnolia grandiflora. It can become an immense tree, growing to 100 feet in its native southeastern United States. It will probably not reach quite that height here because of the lack of natural rainfall in the quantities needed and because of low atmospheric humidity. Still, we can boast some that are at least 70-80 feet. Most gardeners in this area prefer the smaller growing varieties such as St. Mary. Both the species and its varieties take many years to reach ultimate size.

The large leaves can reach 8 inches in length. They are thick, shiny green above, and usually have a rusty tomentum beneath. The showy white flowers are 6-8 inches in diameter and very fragrant. lt is in bloom through most of the summer and fall.

Magnolia grandiflora is most suitable for parks and large garden areas. The named varieties, such as St. Mary mentioned above, may be suitable for smaller areas. It should be kept in mind that the usual watering practices in this area tend to encourage surface roots and the system suggested for Morus alba can be used with this tree also. However, surface roots can be removed if done before they reach 1 inch in diameter.

Morus alba cv. Mapleleaf

Fruitless Mulberry
Among the fastest growing are the fruitless forms of Morus alba. The family with a new home can have usable shade in three years or less by planting this species or one of the varieties The Mapleleaf variety is particularly fast. Trees can be purchased, bare root, from December to March in sizes from 4 to 12 feet tall or more, which gets you off to a flying start. With proper care a tree 20 feet tall and 20 feet across is possible in three years.

As I mentioned at the outset, no tree is perfect in all respects and this one is no exception. The leaves drop every fall, although in a relatively short period of time. Also, they are very large and easy to rake up. Because the tree grows so rapidly, pruning is a yearly chore, particularly in the formative stage. Branches grow to six feet or more in one year and quickly develop a large top which is sometimes too heavy for the young trunk. So stake well, thin jucidiously and head back long branches during the winter months when the structure of the tree is visible.

DEEP WATERING IS ESSENTIAL. A good method is to sink 3 to 4 foot lengths of pipe (about 4” in diameter) into the ground around the tree at 6-foot intervals and about 6 feet from the trunk. Fill with pea stone or larger and let the water trickle in each section of pipe for several hours. This should be done at varying intervals depending on the type of soil.

Surface watering (except when first planted and until the tree is established) will cause surface rooting and its attendant problems However, this method can be used if the top two inches of soil are cultivated the following day so the soil dries out. This will help to discourage surface roots. If the tile method is used, the tiles will have to be moved outward as the tree grows and additional tiles added as the circumference increases as they should be kept at the drip line. Once the tree is established it is fairly drought tolerant.

If you want a dense shade tree 20 x 20 feet in three years, this is your tree. The kids will enjoy climbing in it too. Let them.

Cinnamomum camphora Camphor Tree

For those with a real love of trees and the space to grow them, the camphor is one of the finest trees that can be grown in the warmer areas of California. This native of China and Japan can reach a height of 50 feet or so, with an equal or greater spread. It is beautiful in all seasons, The new foliage in spring may be pink, red or bronze, depending on the tree. The foliage becomes light-green and the leaves turn shiny as the tree matures. Old trees lose their lowest branches and often have a rather swollen base with large roots protruding above the soil. There is some leaf drop most of the year but the heaviest is in March. This is a detriment to some people, but there is no such thing as a perfectly clean tree. If you have ever seen it on a rainy winter’s day when the trunk and larger branches appear black against the yellow green leaves, you will agree that it is truly one of the real aristocrats among trees. No special care is needed in growing the camphor, but as with any plant, the better the soil and care it receives the greater the reward in growth. While not usually bothered by pests it is subject to verticillium wilt, one of the root rots. When attacked by this rot, twigs, leaves, branches, and sometimes the whole center of the tree will wilt and die. For many years nothing could be done to control this disease. Recently a new systemic fungicide, Benlate (benomil), became available and appears to he of considerable value in controlling verticillium when used as a spray on the foliage. In spite of this, camphors are not difficult to grow.

Jacaranda acutifolia Jacaranda

It almost seems superfluous to discuss this popular and widely planted tree. To newcomers who are not familiar with its beauty some information on its culture may be of value. If a really fine tree is wanted, regular pruning and removal of the water sprouts which occur throughout the tree is necessary It is very tolerant of many types of soils, but of course will not do well in poorly drained or highly compacted soils. The work which may be necessary to develop a well- shaped tree is quickly forgotten when the blooms envelop the tree in a cloud of lavender blue and the ground beneath is carpeted with fallen flowers. This Brazilian native graces the streets and gar- dens of many cities all over the warmer areas of the world. In southern California it has been used for many years as a street tree, for park plantings, and in home grounds. Some consider it a litterbug, but for many more its heavy leaf fall is a small price to pay for the wealth of beauty which often comes twice a year. The heaviest bloom is usually in May or June, but frequently there is a secondary blooming in July or August. The foliage is fine and rather fern-like. It is a round- headed tree which can reach 25-40 feet with 15-30 feet spread, occasionally more. It is slightly tender to frost and infrequently is severely damaged by cold. However it grows rapidly and when lightly frosted recovers quickly.

Cupaniopsis anacardiodes Carrotwood Tree

In this day of small suburban lots, suitable small trees are hard to find. The carrotwood is both suitable and relatively small. A moderate to slow grower, it will eventually reach a height of 30 to 40 feet and a spread of about 20 feet. Multiple trunk specimens will have a considerably wider spread. It somewhat resembles the carob, but is more delicate and airy in appearance and has none of the carob’s faults. The leaves are composed of 6 to 10 leathery leaflets, are evergreen, and provide a dense heavy shade. It is probably one of the cleanest trees available today and is fine for use as patio, lawn or street tree. There has recently been evidence of verticillium wilt in heavy soils where drainage is poor or in lawns where poor watering practices are followed. This can be treated with Benlate as mentioned for camphor. The carrotwood can be grown as a single or multiple-trunked tree and the choice is up to the individual planting it. Either way it is a fine evergreen tree and a fine import from Australia, its native home.

Albizia julibrissin Silk Tree

This is another small tree suitable for use in gardens with limited space. Native over a wide part of Asia from Iran to Japan. this deciduous tree is the mimosa of the eastern United States. It is fast growing and can reach a height of 40 feet with an equal spread. However, it can be kept to a much smaller size by regular pruning. The foliage is pinnately compound and in some respects resembles a coarser jacaranda leaf. A really flat-topped tree, it is especially attractive when viewed from above, as the fluffy pink flowers are held above the foliage. It is usually more attractive when grown in its natural form as a multiple-trunked tree. The foliage is light enough so that grass can usually be grown underneath. Its one fault is heavy litter of fallen leaves and flowers beneath. Another tree particularly useful for the deserts of the southwest, it makes a very fine patio tree because of its light, filtered shade and umbrella form. Flower color will vary from light to deep rose pink when grown from seed. An all-around fine small tree which will grow with a minimum of care.

George Spalding has been on the staff of the Arboretum since its inception in 1948 and over the years has served in a number of capacities. Currently botanical information consultant to the public, he is an advisor to Time- Life Books and other publications.

Behind the Scenes

A Behind the Scenes Look… Our members and visitors rarely have the opportunity to visit and get a first hand glimpse of The Arboretum’s greenhouses and nursery facilities. The importance of these facilities to the operation of The Arboretum is immense. Our greenhouses and nursery are used to propagate, grow, and nurture plants for the many collections we currently have and future collections still being planned. Plants obtained for the collections may have arrived into the nursery in the form of seeds, vegetative cuttings or live plants. Often the material comes from private collectors, other botanical institutions, and even from native habitats around the world.
Thousands of Plants Grown
There are literally thousands of plants being grown in our facilities. Some, such as the Ceratonia oreothauma, a close relative of the Carob tree, are nearing extinction or, even worse, are now extinct. Often, arboreta and botanical garden nursery facilities have become the Noah’s Ark for the plant world.
Tropical Plants
At the moment, we are working on developing a collection of culturally significant tropical plants that will eventually find there home in our Tropical Display Greenhouse. These plants are now merely pampered seedlings and/or recently rooted cuttings. Once these plants mature, they will be added to the Display House collections.
Six of our greenhouses are home to one of the largest collection of orchids in the western United States. With approximately 10,000 plants, this collection is of world-class stature and provides blooming plants that can be seen year around in The Arboretum Rotunda and Tropical Display Greenhouses.
Baldwin Bonanza Offerings Most of the plants propagated at The Arboretum for the annual Baldwin Bonanza Festival of Plants Sale are grown in the Education Greenhouse and Nursery. The Education Greenhouse and Nursery is maintained by volunteers and two interns, however, there is always room for more volunteers! Baldwin Bonanza 2002 propagated plants will be selections from The Arboretum’s outstanding collections.
A Fantastic Staff
Last, but certainly not least, a behind the scenes look would not be complete without mentioning our fantastic staff who take care of these facilities. All of the staff has worked very hard in the past year to bring about significant changes in their assigned areas. Julie Norman is our orchid propagator. Julie also has the responsibility of overseeing all nursery operations, including nursery staff management. David Okihara maintains the Display Greenhouses. Thanh Pham, a student professional worker, has been assigned to the accessioning of the orchid collection. Tanya Finney and Sherry Tobin maintain and manage the propagation nurseries and greenhouses.
Behind the Scenes Tour Planned
Those interested in learning more about the greenhouses and nursery facilities will be able to get a behind the scenes tour this winter when the days are cool and memories of 100 degrees have long since past. So, if you long for warmer days during the winter months, a visit to The Arboretum’s greenhouses will certainly warm your spirits. We hope to have a tour date set for the next newsletter. Stay tuned. Timothy Phillips Superintendent

Plant Portraits

David DeardorffLasca Leaves 26:43-45, 1976
It is somehow fitting in this bicentennial year for a plant- portrait article to highlight a species in a distinctive genus of ornamental fan palms named after the “father of our country”. The genus is Washingtonia; it is comprised of just two species: W. filifera, the only palm native to the western United States, and W. robusta.The name Washingtonia was used by Rafinesque in 1818 for sweet cicely, a genus of herbs in the carrot family. Later on it was used by Wendland for the fan palms and was also once used for the sequoias. According to the International Rules of Botanical Nomenclature, no two genera may have the same name, and the oldest validly published name has priority. Since Rafinesque used the name before anyone else, sweet cicely, not the fan palm, should be named Washingtonia. Nearly a hundred years later, however, Parish prepared a taxonomic monograph of the fan palms (Bot. Gaz. 44: 408-434, 1907.). In this study, he decided that the fan palms should retain the name Washingtonia. He made this decision based on what he considered to be sound nomenclatural grounds and also the fact that by this time the use of the name for the palms was solidly entrenched in the literature and in the nursery trade.Washingtonia robusta, the Mexican fan palm, is native to northwestern Mexico and may have been introduced to California as early as the eighteenth century by the mission fathers. It has been noted that Prudhomme grew this palm at his home near San Gabriel and apparently obtained his plants from the mission there. The Mexican fan palm was not extensively planted, however, until around 1870. E. J. Baldwin introduced it in his Rancho Santa Anita in the 1890’s. This planting still exists near the Queen Anne Cottage on the grounds of the Los Angeles State and County Arboretum. Several of these magnificent old palms exceed 100 feet in height and one tops them all at 121 feet. This grand old palm at the northeast corner of the Queen Anne Cottage may well be the tallest palm in the continental United States.Under ideal conditions of good drainage, ample soil moisture, and fertile soil, the Mexican fan palm gains an average of two feet per year in height. At least one record reports a vigorous growth rate of six feet in a single year. It is apparently the ultimate height of the Mexican fan palm which earned it the specific epithet of robusta, since in every other respect it is smaller and more graceful than the relatively massive California fan palm, W. filifera. The smaller leaves, smaller crown, and narrow trunk of the Mexican fan palm result in a graceful habit which is accentuated by the extreme heights it can reach.The leaves of the Mexican fan palm are palmately divided, the divisions extending about one-third of the distance to the base of the blade. The leaves are as much as four feet long, including the stout spiny petiole, and are persistent for several years. The functional life of the leaf is about one year after which it dies and becomes reflexed, dangling down around the trunk in a skirt or petticoat of thatch. The skirts of old leaves persist for years unless pruned away deliberately or removed by wind or fire. When the dead leaves are deliberately pruned, the leaf bases which remain form a very attractive basket-weave texture for much of the length of the trunk.The flowers of the Mexican fan palm are small and whitish, borne in large inflorescences which hang down below the leaves. The fruits are small blue-black drupes with a large seed and very little flesh. The seeds germinate readily and small seedling fan palms often spring up abundantly around reproductively mature trees.The native Americans of the southwest utilized the California fan palm in a variety of ways and, although no specific information seems to be available for the Mexican fan palm in this regard, it may have been used in a similar fashion. The fruits were roasted and eaten or were ground into flour. The trunks were squared off and used as timbers or were split into poles for ramadas and corrals. The leaves provided thatch for roofs and fibers to bind the thatch in place. Thus it may have been for partly utilitarian rather than strictly ornamental purposes that the Mexican fan palm was originally imported by the mission fathers.Whatever the original reasons for its importation, the Mexican fan palm is highly regarded today as a hardy, adaptable, ornamental palm performing well under a wide variety of climatic and cultural conditions. The plants are hardy to 24 degrees and will withstand drought and poor soil, although growth is faster under better conditions. The most widely planted palm in southern California, the Mexican fan palm is now cultivated in Mediterranean and subtropical regions around the world. It is certainly the most abundant tree in the urban landscape of southern California, dominating the skyline of cities and towns from the coast to the desert. It is a stately street tree and, especially when silhouetted against the setting sun, is quite capable of transforming the most mundane urban landscape into a panorama of genuine beauty. Even more than most trees, however, it achieves its true potential when planted in informal clumps and groves in a park-like setting. The magnificent grove of Mexican fan palms near the Queen Anne Cottage on the Arboretum grounds is an excellent example of their quiet grace.Dr. Deardorff is a member of the department research staff involved in taxonomic studies.

What a Gardener Should Know About Fertilizers

Methods of fertilizer application vary somewhat with soil character, moisture present and kind of crop grown.
by Myron S. Anderson 1Lasca Leaves 20:14-15, 1970FERTILIZER IS A TERM that is not easy to define in such a way as to include all the materials sometimes added to soil for the improvement of plant growth. In the general trade, fertilizers for soil improvement fall into three groups, primary, secondary and minor constituents. The primary group includes constituents carrying the chemical elements nitrogen, phosphorus and potassium. Nitrogen is stated on the bag as the element N and is added to promote green plant growth. Phosphorus, stated as the oxide (P205), aids the health of plants, improves growth of roots and to a moderate extent hastens crop maturity. Potassium, also stated as the oxide (K2O), helps the plant to make better use of sunlight and also improves root growth.The secondary constituents include compounds carrying the chemical elements calcium, magnesium and sulfur. Calcium and sulfur are frequently included as a part of the compounds carrying the primary constituents. Thus some of the nitrogen may be in the form of ammonium sulfate that contains a substantial percentage of sulfur. Furthermore, a chemical compound may also have calcium and sulfur in its composition.In some areas soils are deficient in one or more minor elements such as iron, boron, copper, zinc, manganese or occasionally a few others. This lack of adequacy of certain elements in the soil may sometimes be detected by characteristic abnormalities in the appearance of plant leaves. Lowered crop yield as measured by both quantity and quality often results. Misshaped apples due to boron deficiency is a well-known example of the latter. These minor elements are so-called because the quantities present and needed are normally very small. Such constituents as compounds of copper and zinc, for instance, are usually stated as a few parts per million in a fertilizer mixture rather than by percentage as is the case with primary constituents.A GARDENER SHOULD learn to recognize the chemical composition of a mixed fertilizer by the symbols on the bag or box. One of the very commonly used fertilizers of relatively low analysis is designated as 5-10-5. This means that five percent of the weight of the material in the bag is nitrogen. This nitrogen is present as a constituent of one or more chemical compounds in the mixture. The middle number, in this case 10, designates the percentage of the mixture that is phosphorus expressed as the oxide, P205. This is not, however, the chemical form in which the phosphorus actually exists. The third number, 5, represents the potassium of the mixture. The five percent is actually the amount of potassium stated as the oxide.In a 5-10-5 fertilizer, the total quantity of primary plant nutrients thus adds up to 20 percent. The remaining 80 percent is made up of several items. The plant nutrients are in chemical combination with secondary elements or with other materials of non-fertilizing nature. A high-grade fertilizer material such as ammonium nitrate contains about 40 percent of nitrogen available to plants when placed in the soil. The remainder is a chemical carrier, not plant nutrients. A fertilizer such as 5-10-5 also contains materials known as conditioners. These are added to improve the physical condition of the mixed goods, especially to restrain caking. Inert material of low cast, called filler, is added to adjust the mixture to the total percentage stated on the bag.Methods of fertilizer application vary somewhat with soil character, moisture present and kind of crop grown. In many places it is well to apply about 10 to 15 pounds of a mixed fertilizer such as 10-10-10 to one thousand square feet of area. This is plowed or spaded in and the soil properly conditioned for planting. When seeds are planted or small plants transplanted a small handful of perhaps 5-10-5 fertilizer per linear yard is placed in a shallow trench about four inches to one side of the plant row at a depth of four inches. When a second crop is grown without preliminary plowing the rate of application of fertilizer may be somewhat less than that used for the first planting.Fertilizers of different grades are usually carried in garden stores. For best results a gardener frequentiy uses fertilizers of two or more grades. The 5-10-5 material has long been on the market and is widely used for growing many kinds of flowers and vegetables. The 10-6-4 grade is often recommended for use on lawns, while root crops usually respond well to 5-10-10. The 10-10-10 grade serves well to build up garden soil productivity.CARE SHOULD BE TAKEN to use proper amounts of fertilizer for the area involved. The method of application should be suitable. Commercial fertilizers improperly used may burn plants and cause poor germination of seeds.Longevity of the usefulness of fertilizers added to soil depends upon the rate and quantity of water added by rainfall or by irrigation, upon the character of the soil, upon fertilizer constituents dominant in the mixture and upon the quantity of fertilizing materials absorbed by growing plants.In many areas fertilizers may be purchased that are supplied with minor element compounds in adequate yet safe quantities. In the case of tree-crops the appearance of young leaves sometimes give a clue to the likelihood of a deficiency of a certain element. Sometimes a minor element can be better supplied by sprays than in fertilizer applications to the soil. Absorption of a minor element through leaves is often adequate for a current season.The fertilizer needs vary widely from place to place. A gardener should get as much reliable information as practical regarding the need of various constituents for different crops in the area of his garden. Some branch of a state university is usually in position to inform a gardener as to areas where minor element deficiencies are likely to occur and where other specific deficiencies may be expected. Sometimes this agency is in connection with the agricultural extension service, especially in the office of the county agricultural agent. The minor elements of fertilizers in a local garden supply store may provide some hint as to the likelihood of local deficiencies. One should read the chemical analysis on the fertilizer bag and buy the grade of goods that best suits the local garden situation.Dr. Anderson is a retired soil scientist with 40 years’ experience, much of it with the U.S. Dept. of Agriculture, as researcher and author.

Basic Botany: The Disarticulated Lily

Below is an illustration of all the parts of a flower, in this case a lily.

The Cultural Potential of the Hibiscus to Southern California

In Southern California, inadequate directions on the planting and care of ornamental hibiscus given at point of sale are responsible for the early demise of more plants than the periodic ravages of killing frost.The blame should not be placed entirely on the shoulders of the seller, however, for much of the confusion regarding the culture of this popular garden plant is due to its complicated genetic origin.For ornamental hibiscus, as we grow it today, is in reality a highly polymorphic cross-compatible group of species and complex hybrids and their derivatives. The development of garden hybrids began before recorded horticultural history and is being continued in many parts of the world today.Linnaeus, the father of systematic botany, designated this genetically compatible group as H. rosa-sinensis, or Rose-of-China, and although the earliest known development of hibiscus hybrids seems to have taken place there, none of the species involved in the complex is native to China. Most authorities agree that all forms of rosa-sinensis have evolved from the several known species but admit that there may be some additional lost, or not yet identified, species which have contributed to the early horticultural development of ornamental hibiscus.The species which have been identified as progenitors of our modern hybrids are native to several widely distant parts of the world. They vary greatly in plant vigor, growth habit, flower form, and color, and, therefore in cultural requirements, as do their hybrids. For instance, the Hawaiian whites are strong growers and differ greatly from such species as H. liliiflorus, which is indigenous to the South Indian Ocean islands where it is most often found growing wild as an underwood. Exceptional plant vigor almost always results from a cross between the native Hawaiian white and other species or old forms. This is not the case with hybrids resulting from crosses with H. liliiflorus, which is a weaker grower. For this reason, cultural directions should be more specific taking into consideration the genetic history of the cultivar.In our introduction we stated that inadequate instruction at planting time was responsible for the loss of more plants than frost damage. This statement should rightly be qualified, or rather, should be enlarged upon at this point By frost damage we mean total loss resulting from the freezing of the plant by the extremely low temperatures that periodically occur in many areas of the Los Angeles Basin. This kind of damage is not to be confused with winter losses which are the direct result of faulty selection of planting sites, time of planting, and improper cultural practices, particularly during the late fall and winter.The usual instructions available to the homeowner do not emphasize the fact that in Southern California soils become progressively colder during the winter months and often do not really warm up until June. Modern hybrid hibiscus are particularly susceptible to “cold feet,” particularly when subjected to excess moisture, and are therefore less able to resist sudden drops in temperature or other adverse conditions. In Florida, on the other hand, hibiscus plants will often recover from even severe frost damage because the soils of that state never become very cold despite the catastrophic frosts that sometime occur.In the Los Angeles Basin there are many different thermal areas, some of which are, for all practical purposes, frost free, and others where even the hardiest cultivars will not survive periodic frost damage. Slight differences in elevation, air drainage and other factors affecting temperature often exist quite close together; in some cases they may be found on a single house lot. On my own hillside home in Los Feliz, hibiscus plants have never suffered frost damage in the higher spots, while lower plantings have been lost.It follows that nurserymen should know the approximate temperature conditions in the general area they serve and should advise their customers accordingly. From a practical standpoint such advice could cause some loss of immediate sales, but in the long run would prove profitable. Sydney, Australia, like Los Angeles, has both thermal belts and areas where frosts occur nearly every winter. Some years ago, a Sydney nurseryman decided to specialize in hibiscus. He realized, however, that to be successful he must have customers who themselves were successful with the queen of tropical flowers. He therefore made a survey of the locality which he served, and learned the approximate limits of the thermal belts where optimum conditions for ornamental hibiscus prevailed. He then published this with cultural directions for distribution to prospective customers. His varietal recommendations, too, were based on his findings. The high sales enjoyed by the enterprising nurseryman and the subsequent incidence of hibiscus in Sydney gardens testify to his success.Unfortunately, there are not a large number of varieties of hibiscus propagated for sale in Southern California. Those that are consist mainly of the older hybrids which have been in the trade in this country and Europe for over a hundred years. However, one large producer does make periodic introductions of new varieties on an exclusive basis, usually as patented plants.Reasons for the limited offerings of hibiscus varieties are both cultural and economic. Thirty years ago the list was very much longer, but at that time growers could economically produce grafted hibiscus, just as they do now in most other areas where hibiscus is popular. Today producers say that only cultivars which will root easily from greenwood cuttings and which grow well on their own roots can be economically produced for the retail outlets. Thus most of the highly complex hybrids, such as those in Hawaii, are not considered by local wholesale growers.Limiting the propagation and sale of hibiscus cultivars to proven hybrids does have the advantage of insuring the offering of only such plants as will survive extreme temperatures in most years. But breeding work, such as has been done at the Los Angeles State and County Arboretum in recent years, has resulted in the development of many equally satisfactory hybrids for this area, both in flower quality and plant vigor. Unfortunately, these could not be turned over to individual nurseries on an exclusive basis, and the larger producers say that, as a general rule, they must have this advantage to offset the high cost of advertising and building up stock. Because of these economic factors the results of breeding work have not been fully exploited.Further, there are many suitable cultivars for our area available in Florida and elsewhere which have not been given a commercial trial here. Unless they are given sales-exposure by the nursery trade they will never be known to the public. In Florida, the several annual hibiscus shows held by the various local chapters of the American Hibiscus Society bring out hundreds of new cultivars. There are many Florida nurseries specializing in hibiscus, most of them offering a long list of varieties. Some of these were developed by the writer here, but were not found acceptable by the local nursery trade. The same situation prevails, in a lesser degree, in Australia, where interest in hibiscus has increased tremendously in the past decade. This has been the case particularly in Queensland.As we have pointed out, cultural directions for hibiscus should take into consideration the genetic background of the cultivar. In the following paragraphs, brief general instructions are given for common varieties, with pointers on the specific requirements for some of them.
Well-drained Soils a First Requirement
The average homeowner has little choice of soil types, but he can improve that which is available to him. It is not easy to create better drainage conditions in the heavier soil types. Nevertheless, some effort should be made, particularly in the case of the heavy clays (adobe), because it is difficult to establish hibiscus in such soils. There are inherited reasons for this: most of the species from which modern hybrids were originated are native to areas having soils of volcanic origin, which are naturally well drained. A few specific instructions on this subject will be covered later under the discussion on watering and winter care.
Planting Directions
Full sun is not always available to the homeowner, but hibiscus do equally well in morning sun and afternoon shade, an environment usually found on even the smallest house lot.The planting of hibiscus in lawns and other areas where heavy applications of water are made exposes plants to “wet feet” and therefore a high incidence of winter loss. Perhaps the most attractive home planting is a hedge or border of a single variety, particularly if one of the more vigorous growers is selected and is kept in hand with the pruning shears. The popular White Wings is particularly effective for such use as it is a profuse bloomer over a long season and the foliage as well as the bloom is attractive. It can be pruned shapely at almost any time of the year. It can also be trained as a standard and in this form its growing habit makes it particularly desirable.Unfortunately, there are too few low growers available, the only form that is really suitable for mixed shrub borders. To stand alone, Crown of Bohemia should he selected. Ross Estey is also attractive as a single planting with low growing shrubs of annuals.
Time of Planting
The best months to plant hibiscus depend on the variety and the age and size of the plant. Most growers propagate during the winter and spring, offering plants rooted at that time for sale during the summer and fall. If these plants are planted early enough, that is, not later than September 1, they will become established before the cold weather sets in and are thus able to withstand cold winter soil temperatures. My personal preference is for older plants, setting them out in April or May. Not much growth can he seen the first several weeks, but as the weather warms up the plant gets the benefit of a full growing season before it is exposed to winter temperatures. If late planting is necessary, then the selection of year-old plants in gallons, or older plants in three- or five-gallon containers should be considered. If such plants should appear to be rootbound in the container, a judicious amount of root pruning should be resorted to before planting. Properly done, this will not affect the growth of the plant. In heavier soils it is good practice to put five or six inches of pea gravel in the bottom of the hole before planting, then to fill in with a light soil into which has been incorporated a gallon-can-full of steer manure and a tablespoon of a balanced commercial fertilizer. One readily available mix is that sold as a dichondra food.
Pest Control
Pest control is particularly important during the first year when, it is hoped, the plant will he growing fast. But except for some unusual insects or virus, control can be maintained with a strong spray from the sprinkler. For the record, I was using this method of pest control long before most of the ubiquitous antipesticide partisans were born!
The best time to prune ornamental hibiscus is a frequent subject for debate. But here again the genetic origin of the hybrids must be taken into consideration. First-generation hybrids from almost any interspecific cross, or with a species as one parent, usually show extreme hybrid vigor. This is noted in Agnes Galt and Kona, both of Hawaiian white parentage. Ross Estey is a third-generation hybrid from the same species and it, too, must be kept in hand with the shears. Crown of Bohemia is also a strong grower, but is quite well behaved and seldom becomes “leggy.” The same is true of California Gold. But the common red, called Brilliant, and most other old varieties need attention if they are to keep in shape and flower as they should. Some years ago, before the larger nurseries began to propagate hibiscus from greenwood tips under the mist system, most stock was produced by smaller growers who were not so choosy about the cutting material. lt was the common practice at that time for gardeners hired on a maintenance basis by householders to prune hibiscus under their care in December and January. They then took the prunings with them and either sold them for cutting mate- rial to nurseries, or propagated plants themselves as a backyard venture.Pruning in December and January is an extremely dangerous practice in almost all cases, but particularly so in marginal growing areas. Cutting back sharply, as was usually done by gardeners, is a shock and weakens the plant at a time when it is most susceptible to winter kill. It seems to be the consensus of most experienced and responsible gardeners now to cut back hibiscus a little at a time, thinning out the plant and topping back vagrant growth, then shaping up the plant in early spring after the danger of frost has passed.
In Southern California hibiscus thrive best in a soil with a pH of about 5.5 or 6, but only through experimentation with one’s own soil can this balance be effected.My personal preference for year-round feeding is a commercial mixture of about 4-8-8 with a side dressing of blood meal each month. The high acid fertilizers should be used sparingly as they can cause bud drop. Frequency of application, too, must be guided by experience. The most important point to remember is that hibiscus are good feeders, and both the length of the blooming season and the amount of bloom can be increased by adequate use of plant foods. Most hibiscus in Southern California are undernourished and overwatered.
As a general rule, hibiscus should be given generous applications of water as needed, rather than frequent light sprinkling. Early in the summer, when the soil begins to warm up, individual basins should be worked up around each plant or, in the case of row planting, around several plants. These basins should be filled with a quantity of water sufficient to assure thorough soaking of the roots. In the winter months, however, the basins should be filled in and the soil mounded up around the base of the plants so as to drain the water away during the rainy season. For plantings in heavy soil, a sheet of polyethylene of sufficient size to cover the root zone will help to keep the soil warmer and better drained. In light soils during extended dry seasons in winter, the cover can he removed and the plants watered sparingly. The objective of this winter-care program is to force the plants into a winter resting period.
Container Culture
So far, we have been discussing the planting and care of hibiscus varieties easily available in Southern California. For the venturesome, there exists the possibility of enjoying even the highly complex hybrids such as are grown in Hawaii, Florida, and other more favored areas for hibiscus. This calls for growing the plants in large containers which can be moved into shelter during the winter months if necessary.Almost any variety of ornamental hibiscus will do well in containers, even those as small as 12 inches in diameter. The restriction of the roots does not seem to affect growth or bloom just so long as the plant is adequately fed and watered. The English nurserymen and fanciers grow hibiscus this way out of necessity, and in England one sees huge plants, many years old in 18- to 20-inch tubs.While a small amount of greenhouse or lathhouse space is handy for winter storage, such an arrangement is not necessary. The only requirement is that plants are not exposed to freezing temperatures in storage and, where it is to be a dry storage, a judicious amount of cutting back is done.During the summer the potted or tubbed plants can be placed almost anywhere in the garden or patio. Members of the American Hibiscus Society who live in the colder parts of the South plant in clay containers from which the bottom has been tapped out. In early summer these are planted outdoors in the soil just as they are. Forced along, they usually produce blooms for several weeks before the danger of freezing requires the gardener to remove the container from the soil, cut hack the roots which have grown through the bottom, and place them in winter storage.For those who are interested in growing hibiscus in containers, a membership in the American Hibiscus Society will he extremely helpful. The annual dues, which are five dollars, include a copy of the quarterly, “Seed Pod.” This spritely, well-edited publication carries a wealth uf cultural and other timely material, together with advertisements of nurseries specializing in hibisus who will ship to California. Stock must necessarily come in either as scion wood or bare root. In the former case, if a small area of bench space in a greenhouse is not available for rooting cuttings, it will he necessary to master the simple rules for grafting hibiscus. In some cases the proper conditions can he developed for propagating such material be use of a small rooting outfit heated by a short heating cable, and covered with polyethylene. These can usually be secured through local nurseries or supply houses.Ross H. Gast has been working with ornamental hibiscus for over 35 years. In pursuit of his avocation he has traveled all over the world, notably among the islands of the South Pacific and South Indian Oceans where he rediscovered several species that became the parents of hybrids he developed and introducecd in Florida, Australia and Southern California. A veteran editor and publisher, Mr. Gast has written numerous articles for foreign and American journals, including Lasca Leaves.   

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© 2024 Los Angeles County Arboretum and Botanic Garden • 626.821.3222 • 301 North Baldwin Ave, Arcadia, CA 91007

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Phone: 626.821.3222

301 N. Baldwin Ave, Arcadia, CA, 91007