A Rare plant that is common in cultivation

Eucalyptus crenulata is a small, crooked tree with dense blue-green foliage, and rough, fissured bark.  Its natural distribution is restricted to two small areas near the towns of Yering and Buxton, north-east of Melbourne.  The vegetation at both sites is a woodland, with an understory of small-leafed shrubs and coarse sedges, which grows on seasonally waterlogged soils near river floodplains.  The populations are small (fewer than 700 individuals in total on a combined area of less than 50 ha), surrounded by farmland, and the vegetation is highly disturbed with 20-50% of the understory species made up of non-native plants.  Recent research has suggested that the mature trees of the Yering population (about 40 km north-east of Melbourne) are probably hybrids between Eucalyptus crenulata and Eucalyptus ovata (Swamp Gump) so the only pure stands are at the larger and less disturbed Buxton site. 

With credentials like these it is easy to see why Eucalyptus crenulata has been classified as endangered in Victoria and Australia.  Nevertheless, the distribution map map below shows that this species has been recorded in many more places than the two isolated sites where it is native.  This is because Eucalyptus crenulata has become popular in cultivation and widely planted.  Individuals from the planted sites have escaped and are now growing and reproducing some distance away from their place of origin.

Most eucalypts that grow in temperate parts of Victoria are naturally quite tall, relatively sparsely-branched, have narrow green leaves that hang vertically, cast little shade, and produce flowers only on the tips of branchlets.  Eucalyptus crenulata is one of a few species which deviate from this norm.  The dense, broad leaves, which are covered by a pale blue-green wax when they are young, and the cream flowers clustered in leaf axils have made them a popular ornamental tree.  They are particularly good for smaller gardens where drainage is poor, or for roadsides where there are overhanging powerlines.  They are available from a wide range of nurseries across Victoria and other parts of Australia, and have found their way into New Zealand, Canada, northern USA and Europe (a French company sells them on the web).

There are many more individuals of Eucalyptus crenulata in cultivation than there are in the wild - in fact there are more in a single suburb in Melbourne's south-east.  There are also more growing wild in areas to which they are not native than are in their natural habitat.  Sadly most of the plants that grow away from Yering and Buxton are bigger, brighter blue, more densely foliaged and more robust than the originals.

This is not an unusual situation as there are many species that are rare in their natural environment - or at least uncommon - that have become much more abundant in cultivation.  Victorian examples include Grevillea barkleyana, which is native to a tiny area north-east of Melbourne but has become an extremely popular cultivated species.  The Western Australian tree, Corymbia ficifolia (Flowering Gum) has a natural range of about 1 km², but is one of the most widely planted eucalypts in the country. 

Sometimes the cultivated species invades new areas so successfully that it becomes an environmental weed.  For example, Pittosporum undulatum (Sweet Pittosporum) is native to, and an important component of, rainforests of East Gippsland but its popularity in cultivation has turned it into one of the most disliked of environmental weeds around Melbourne.  The Cootamundra Wattle (Acacia baileyana) is another serious environmental weed in Victoria and other states but its home range is a very small area near the town of Cootamundra in NSW.  Two of Victoria's most important imported tree species, Pinus radiata (Monterey Pine) - the mainstay of our softwood industry - and Cupressus macrocarpa (Monterey Cyprus) - a major windbreak and parkland tree - are both threatened in their home state of California.

Clearly when a plant is rare and has a quality about it that is attractive for cultivation there is always the potential for the species to become more common away from its place of origin.  If the original populations then become threatened it is logical that the long-term survival of the species will come to rest more heavily on the cultivated forms.