By James E. Henrich, Curator of Living Collections

The Arboretum is continually acquiring new species, creating an ever-evolving, dynamic living collection. Time, climate, environmental conditions, quality of maintenance, to name a few, selectively eliminate those not adapted to our conditions. The selection process yields strong, average and poor performers from the remaining plants.

Let’s look at some examples from the Australia collection which is ideal for this discussion. Why? Our species come from nearly every territory in Australia, ranging from the southwestern Mediterranean zone to seasonally dry forests of Queensland and New South Wales. The species are highly adaptable and well suited to the climate of Southern California. An additional advantage is drought tolerance, a trait that is characteristic of plants from Mediterranean climate zones.
One goal for the living collection is continual diversification while, at the same time, respecting the value of stalwart species. Tasmanian blue gum (Eucalyptus globulus) is a good example of the latter. Our oldest specimen dates to the early 1860s. The number of specimens of Tasmanian blue gum has declined due to old age, pests or pathogens, making it is a prime candidate for re-introduction to the collection. This is done to establish a new generation, a practice similar to the management plan for our Engelmann oak grove.

Species recently planted in the landscape include: red-flowering gum (Eucalyptus ficifolia [now Corymbia]); Forrest’s marlock (E. forrestiana) and coral gum (E. torquata). Specimens of each exist in the landscape already, but some are aging or not performing well. Each has stunning characteristics that make them valuable. Red-flowering gum has extremely variable flower color including white, pink, orange and red. Forrest’s marlock was acquired and propagated unsuccessfully ten times between 1949 and 1986 until one 1986 accession was established successfully, with one more individual this year. It has stunning fuchsia-colored ovaries and bright yellow stamens. Coral gum is a small to medium-size tree with coral-pink stamens and tangerine to red ovaries; it can flower in two years from seed.

The first chart below features Eucalyptus species new to our current living inventory. Of note are these species: Nundroo gum (Eucalyptus calcareana) with smooth bark and ribbons of cream, gray and orange-tan; Bendemeer white gum (E. elliptica) with striking chalk-white bark; and Webster’s mallee (E. websteriana) with beautiful cinnamon-red curling bark and cordate leaves. Seeds of these species will be put into production in the near future and plants will begin appearing in the landscape in the next year or two. For an expanded version of the species discussed in this article and more, see our web site.

James E. Henrich is Curator of Living Collections at the Arboretum.

Newcomers: Eucalyptus species

Scientific Name Common Name Distinguishing Trait
Eucalyptus approximans Barren Mountain mallee Steely gray-green or white bark
Eucalyptus arachnaea black-stemmed mallee Multi-trunked tree with black bark
Eucalyptus calcareana Nundroo gum Smooth bark with ribbons of cream, gray and orange-tan
Eucalyptus cernua red-flowered moort Red flowers, shrub
Eucalyptus deanei Deane’s gum New bark bright yellow
Eucalyptus delegatensis alpine ash Upper bark whitish to yellow-gray
Eucalyptus elliptica Bendemeer white gum Bark striking chalk-white
Eucalyptus kartzoffiana Araluen gum Juvenile leaves are intense bluish color
Eucalyptus lesouefii Goldfield’s blackbutt Distinctive black basal “stocking” of bark
Eucalyptus ligustrina privet-leaved stringybark Bark gray to red-brown
Eucalyptus michaeliana Hillgrove gum Eye-catching mottled bark
Eucalyptus microcarpa inland gray box Typical box-type bark
Eucalyptus paliformis Wadbilliga ash Bark gray to olive green with chalk white
Eucalyptus pilularis blackbutt Rough fibrous bark
Eucalyptus rudis flooded gum Rough bark on trunk and smooth gray bark on branches
Eucalyptus sieberi coast ash Bark of young trees flaky, orange-brown
Eucalyptus sturgissiana Ettrema mallee Restricted to sandstone plateaus in NSW
Eucalyptus utilis coastal moort Large white flowers, restricted to south coast of Western Australia
Eucalyptus websteriana Webster’s mallee Beautiful cinnamon-red curling bark and heart-shaped leaves

Our Australian Stalwarts

We have placed emphasis on rejuvenating the Australian collection because of its long-standing diversity and historical significance among public collections. Let’s look at this collection for a comparison of species that have persisted for many decades, ones that have been added recently and those that are new to the collection. The table below features a selection of species that have thrived for decades, diminished in number of specimens and new additions. It contains scientific name, common name, year accessioned and planted (persisted in landscape), and year accessioned & short lived (either in the landscape or the nursery). The fourth column contains years for accessions that never left the nursery or specimens that lived only very briefly in the landscape—see comment below table for reasons. It becomes apparent that desirability is often a factor driving the frequency of acquisition exemplified by E. ficifolia, E. macrocarpa, E. torquata, X. quadrangulata.

Name Common Name Acc. & planted Acc. & short lived*
Acacia glaucoptera Clay wattle 1986s, 1991c, 1999p, 2002p 1974s, 1978c
Angophora costata Smooth-barked apple 1953s, 1954s, 1964s 1969s, 1950s, 1959s, 1978s, 1985p
Callistemon citrinus ‘Jeffers’ Bottlebrush 2009p None
Callistemon viminalis ‘Harkness’ Bottlebrush 1968c, 1972p, 1977p 1968c
Eucalyptus diversicolor Karri gum 1954p, 2004p 1951s, 1953s, 1954s, 1954s, 1958s, 1967s
Eucalyptus ficifolia (Corymbia ficifolia) Red-flowering gum 1949s, 1954s, 1960s, 1967p, 1971p, 1983p 1988s, 1997p, 2002p, 2002p, 2006p 1948s, 1949s, 1951s, 1953s, 1954s, 1956s, 1957p, 1957p, 1958p, 1960s, 1967p, 1969p, 1970p, 1970s, 1970p
Eucalyptus globulus Tasmanian blue gum 1948p, 1955s, 1999s 1950p
Eucalyptus gunnii Cider gum 1966s, 1979s 1950s, 1953s, 1956p, 1971s
Eucalyptus macrocarpa Coolgardie rose 1957s, 1985s, 1986s, 2005s, 2006p 1949p, 1949s, 1949s, 1953s, 1956s, 1957s, 1958s, 1959s, 1969s
Eucalyptus torquata Coral gum 1950s, 1963s, 1969s, 1986p, 1986s, 1986s, 1997p 1949s, 1950s, 1959s, 1963s, 1965s, 1980p
Geijera parviflora Australian willow 1951s, 1955s, 1970p, 1981p, 1988p 1980p
Melaleuca linariifolia Flax-leaf paperbark 1954s, 1959s, 1997c 1951s, 1955p, 1960s, 1965s
Xanthorrhoea quadrangulata Grass tree 1951s, 1971s, 1972p, 1981p, 1987s, 1989s, 1996s, 1998p 1960s, 1975s, 1975s, 1975s, 1976s, 1980s

Legend: c=cutting, p=plant; s=seed
Alive in the most recent inventory
Species planted in 2016
*=did not get planted in the landscape because of the following: not propagated; failed to germinate/root; died in the nursery; remained in the nursery too long resulting in a deformed specimen; frost damage; poor care; hit by a truck
1948 is the year LASCA was incorporated
1949 is the first year new germplasm was acquired, accessioned, planted

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