Eucalyptus rydalensis R.T.Baker & H.G.Sm.
Eucalyptus aggregata, commonly known as black gum, is a species of Eucalyptus endemic to southeastern Australia. A medium-sized tree with dark bark and white flowers over the summer and autumn, it is a component of grassy woodland, often in low-lying or swampy areas. Much of its natural habitat has been cleared and it is under threat.
The black gum was first described by Henry Deane and Joseph Maiden in 1900, with material collected at Wallerawang as the lectotype. The species name aggregata is Latin for "clustered", referring to the fruit.
The black gum grows as a medium-sized tree, reaching 18 metres (59 ft) in height, with dark grey to black rough bark, which is fibrous and flaky. The glossy green leaves are alternately arranged along the stems and measure 5–12 centimetres (2.0–4.7 in) long by 1–2 centimetres (0.4–0.8 in) wide. They are the same colour on both surfaces. Arranged in groups of seven, the white flowers appear from November to May. Each flower head is around 1 centimetre (0.4 in) in diameter.
Distribution and habitat
It is a rare species found from Capertee and Bathurst in central New South Wales, south through central and southern tablelands, with an isolated population near Woodend in Victoria. It has a very patchy and scattered distribution, as much of the land throughout its range has been cleared for agriculture. Eucalyptus aggregata grows in woodland and is associated with candlebark (Eucalyptus rubida), ribbon gum (E. viminalis), black sally (E. stellulata) broad-leaved peppermint (E. dives) and snow gum (E. pauciflora), with a grassy understory of river tussock (Poa labillardieri) and silver top wallaby grass (Joycea pallida). The soil is generally poorly drained, alluvial or swampy, with the black gum growing in low-lying areas. These are also natural frost hollows, where cold air persists in the cooler months. It is found at altitudes above 700 metres (2,300 ft), where there are heavy frosts and snow in winter.
Conservation and threats
Most of the extant population, estimated at 6300 to 8100 mature trees, are isolated. Their seedlings cannot compete against surrounding weeds. These trees are also threatened by hybridisation with E. viminalis and E. rubida. Climate change may also reduce the extent of frost hollows as the climate warms. The NSW Scientific Committee of the Department of Environment and Heritage in the New South Wales Government have proposed the black gum be listed as vulnerable.
Although its soft timber is of little use, the species is versatile in that it grows in other areas where few other local species thrive, and can be a useful shade tree with its dense canopy. Its foliage can be used as fodder.
- "Eucalyptus aggregata H.Deane & Maiden". Australian Plant Name Index (APNI), IBIS database. Centre for Plant Biodiversity Research, Australian Government.
- Elliot, Rodger W.; Jones, David L.; Blake, Trevor (1992). Encyclopaedia of Australian Plants Suitable for Cultivation: Vol. 4: Eu-Go. Port Melbourne: Lothian Press. p. 16. ISBN 0-85091-213-X.
- Hill, Ken. "New South Wales Flora Online: Eucalyptus aggregata". Royal Botanic Gardens & Domain Trust, Sydney, Australia.
- Benson, Doug; McDougall, Lyn (1998). "Ecology of Sydney plant species:Part 6 Dicotyledon family Myrtaceae" (PDF). Cunninghamia. 5 (4): 809–987. Archived from the original (PDF) on 2009-06-14.
- Major, Richard (28 February 2011). "Eucalyptus aggregata - proposed vulnerable species listing". Environment & Heritage. New South Wales Government. Retrieved 21 March 2012.