Author: Susan Parsons
The Camden white gum (Eucalyptus benthamii) is considered a threatened Australian native species, native to the Nepean River and tributaries near Camden in New South Wales. This status was, in part, a result of the construction of the Warragamba Dam in 1933 that flooded a large area of its habitat. The species was well known to Aboriginal people of the area who called it durrum-by-ang.
The species was listed as a vulnerable in the EPBC Act as at 16 July 2000.
Camden white gum has been planted as one of the forests at the National Arboretum Canberra. In December 2011, Ezekiel Ochieng, M.Sc Forestry, who is working with the ACT Government, said that a total of 2,335 Eucalyptus benthamii trees had been planted with 1,983 trees planted from landscape tubes in 2007-8 and 160 in 2009.
Seeds had been sourced in 2006 from the Australian Tree Seed Centre CSIRO who supplied 5g of seed which had been collected from 25 mother trees in a seedling seed orchard located at Barclays, Deniliquin in New South Wales. Seedlings for the Arboretum were raised at Yarralumla Nursery in Canberra. Stock Control Officer at the Nursery, Cheryl Gregory, said additional seeds have been obtained for an expanded planting of 192 trees. These seeds came from ten mother trees at Kedumba Valley in New South Wales.
Apart from damage by kangaroos, which resulted in the replacement of 114 trees, the species has performed exceptionally well at the Arboretum. The Friends Tree Measurement Group last measured trees in the planting on 22 November 2009. At that stage the average height varied from 0.64m (younger plantings) to 2.83m for the 2007 plantings. Average diameters for the earlier plantings were 9.34cm.
The original plantings were placed at a spacing of two metres within rows and four metres between rows. This was done with the objective of later increasing the spacing through thinning some trees to reduce competition between individual trees and produce a healthy forest. Thinning was conducted on the older stands and will be repeated sometime in the future as the other younger stands start to exhibit signs of competition.
Curator at the Arboretum, Adam Burgess, says this forest is especially important to the National Arboretum as it was the first forest planted. He remembers clearly planting the first tree and admiring the surrounding topography picturing the future Arboretum that was then on its way. Burgess says now, when you stand in the same spot five years later, all you can see is a Eucalyptus benthamii forest.
In this writer’s home library was a newspaper clipping dated 2 July 1994 from “The Weekend Australian” newspaper which referred to work done in connection with Eucalyptus benthamii by Dr Craig Gardiner and Dr John Larmour at Kedumba.
We contacted the information officer at the CSIRO, Marian Sheppard, who explained that Dr Gardiner was no longer employed with CSIRO and that his replacement as manager of the Australian Tree and Seed Centre was Sarah Whitfield.
We were given reference to reports published reports, “Seed collections and ex-situ conservation measures for Eucalyptus benthamii from the Kedumba Valley” (1995) by Gardiner, C and Larmour, J. (CSIRO Division of Forestry, Canberra) and “Seed collections of Eucalyptus benthamii, Kedumba Valley” (1993) Larmour, J. (CSIRO Division of Forestry, Canberra).
This project was a “Water for Healthy Country” initiative for which the current communicator is Mary Mulcahy of the CSIRO.
Dr Larmour was out of Canberra with work but he promptly responded to our query that the E. benthamii project, “It was one of my memorable seed collections trips into a beautiful and spectacular part of Australia. We managed an extensive collection of about 100 individual trees and (this) has proved a collection of considerable interest both internationally and for domestic conservation.”
Sarah Whitfield, Manager, Australian Tree Seed Centre at CSIRO Plant Industry, provided us with a report on seedling seed orchards of Eucalyptus benthamii located at Deniliquin, NSW, which are a partnership between CSIRO Plant Industry, Riverina Trees and local land holders. Their original aims were to produce commercial quantities of improved seed and to serve as part of a base population for selection of parent trees for breeding. She also passed on a report on a seedling seed orchard of E. benthamii located at Kowen, ACT, which is a partnership between CSIRO Plant Industry and Environment ACT, which had similar aims.
The two sites near Deniliquin were established in 1995. Originally established as trials to test for superior provenances, families and individuals, they were measured and selectively thinned in 2000 and 2002, converting them into seedling seed orchards. Selection was based on stem volume, leaving only the best trees for seed production. High quality E benthamii seed is now being produced from these orchards for sale to plantation growers within Australia and overseas.
The site at Kowen was established in 1995 as a trial to test for superior families and individuals, it has been measured once every two years and selectively thinned in 2001, converting it into a seedling seed orchard. Selection was based on stem volume, straightness and branch characteristics, leaving only the best trees for seed production. The orchard incorporates 48 families of E. benthamii sourced from the species’ largest natural population, the Kedumba Valley, west of Sydney NSW. This population is both isolated from the few other natural stands of the species and limited in numbers.
Sarah Whitfield also advised that Penny Butcher, formerly CSIRO, has written papers on the genetic variation between the three different populations of this species. The Australian Tree seed Centre currently holds seed from the majority of the genetic resources available for this species.
On 27 February 2012, Whitfield said that the Australian Tree Seed Centre’s main reason for working with E. benthamii is from a biodiversity conservation stance, not so much to produce commercial quantities of seed. The orchards were originally established as conservation stands, however the Forest Industry in Australia and overseas have now shown an interest in growing this species for timber, pulp and bioenergy production on marginal sites.
In “Buildings & Landscapes: The Australian National University, Canberra” (1996. ANU) Dr John CG Banks and Mads Gaardboe give an appendix reference to, “Eucalyptus benthamii var. benthamii (Camden white gum) as a medium-sized, riverine, forest tree restricted to the Nepean river system. It has a smooth white bark to ground level, concolorous leaves and seven flowers in the inflorescence, the capsules are bell-shaped with a thickened rim, valves slightly exsert. Closely related to the manna gum. New plantings on north side of Sullivan’s Creek.”
We contacted Melinda Walker, University Arborist Gardens and Grounds, of the ANU and she sent us a map showing the location of the trees near Burgmann College at the end of Daley Road.
Walker planted the trees herself and, although the University does not have tree planting records that go back that far, she was fairly certain they were planted around 1996 when John Banks was working on the book.
There were originally about ten trees of which seven remain. The old ANU tree database records that on 15 January 2003 the threes were in good health and 6m tall.
Melinda Walker provided a Tree Report on one of the trees that was inspected on 20 December 2007 when the tree identified in the report was 17 metres high, semi mature, in good health, of high significance.. The writer of this Tree Story visited those trees in December 2011. Their riverine location on the slopes of the creek is very appealing. For this Tree Story, Walker measured the tallest tree on 27 February 2012 and it is 18m high.
Environmental and horticultural consultant Geoff Butler has also told me of a good stand of E. benthamii on the ‘Cherryburn’ property in the Majura Valley. The property is a private rural lease. The species is present in some windbreaks that have been established at ‘Cherryburn’ and the trees are performing particularly well. The windbreaks are readily seen from Majura Road and are located at the northern end of the valley.
Camden white gum is planted at the Australian National Botanic Gardens in Canberra. On a visit to the Gardens in January 2012, Dan Marges directed me to a specimen on the Eucalypt Lawn. The tree is close to the path that bisects the lawn, on the right leading to the Ducrou pavilion. Marges says this E. benthamii is 25.5m high and its diameter at breast height (DBH) is 1822mm.
Paul Carmen from the Gardens has shared the collection notes, dated 26 September, 1979, by J.D. Briggs, on the eucalypt and we reproduce part of them here. Collection site was Kedumba Valley, lower reaches of Reedy Creek, 2.4km south of Kedumba Homestead, altitude 160m. A narrow belt of E. benthamii extends for a few kilometers along the creek. A tall white gum, 33m high, DBH 60cm, 3m of brown, flaking bark, then a smooth white stem. Voucher for painting of Endangered Eucalypts for ANPWS by [botanical illustrator] Marjorie May, 1981, voucher for drawing of fruits for Flora of Australia, by M. May 1981.
These details will bring a shiver of excitement to anyone who loves trees – the thrill of the search, the collection, then a specimen of an endangered eucalypt which is now 30-32 years old.