Corymbia (Eucalyptus) citriodora
Family: Lemon-scented Gum
Blackwood has an extensive native range, extending throughout southern Victoria into Tasmania. Blackwood is also found on the basalt plains north of Melbourne where it is found in mixed populations with A. implexa, Lightwood. In these northern habitats, Blackwood does not reach the same very tall size found in the Otways, Tasmania and along the south-east coast of Victoria, often reaching only 10-12m tall. In cultivation, most Blackwoods will grow to only 12-15m, although if the site is ideal, they may reach 20m. Blackwoods are strong-wooded trees, and do not shed limbs as frequently as other wattles or some eucalypts. They are long-lived, often living over 100 years.
Blackwoods are known for their long life, low suckering habit, elegant dark grey-green foliage, and abundant winter flowers. The flowers appear in late winter, and are multi-branched inflorescences of pale yellow balls. The fragrance is sweet. The bark of Blackwoods is dark brown, deeply furrowed, and not typical of many wattles.
Siting of Blackwoods requires soils that have either extremely free drainage or an abundance of organic matter and moisture. These trees probably will not succeed on many dry compacted sites, and if grown in streetscapes, will require an extensive root run. Blackwoods are not suited for narrow nature strips or under power lines (or verandahs).
A. melanoxylon is an excellent indigenous plant for Melbourne if grown in adequately-large areas where both roots and canopy can grow to full potential.Lemon-scented Gum is one of the most popular Australian trees grown in Melbourne. Originating from a very restricted area in Queensland on the Tropic of Capricorn, Lemon-scented Gum has grown very well on many Melbourne sites. This tree is typified by its tall, upright habit, long elegant foliage, and smooth grey bark. Further, the lemon-scented foliage and flowers are of great interest throughout the year.
C. citriodora seems to grow on most sites in Melbourne. It is tolerant of dry, sandy sites, seems to tolerate moist, high-clay-fraction locations, and grows rapidly both with and without water. Occasionally it may be troubled by lerp, but is not badly affected at any time. C. citriodora is intolerant of frost when young, and trees less than 1m tall can be badly affected in northern and highland areas.
There are no selections of C. citriodora currently available, although performance with this tree may vary; this results from interbreeding between C. citriodora and the closely related C. maculata (Spotted Gum). Frequently trees with strongly-spotted trunks may grow in a seedling tray of C. citriodora, showing the obvious hybridisation between these two species. To assure best growth and true-to-type plants, Metropolitan Tree Growers are using seed from the CSIRO orchard, located in Castle Hill NSW.
Corymbia citriodora ‘Dwarf’ is a selected form of Lemon-scented Gum that has been grafted at Humphris Nurseries to allow the clonal expression of its desirable attributes. Grafted trees are typically smaller than seedling grown specimens.
Corymbia citriodora grafted Dwarf is expected to grow to around 7 m high in the Melbourne area. It will have the same environmental tolerances as the species but can be used in locations where space is more constrained.
Typical mature height: to 20m in Melbourne
Useful in: avenues, parks
Sites for best growth: most soil types, full sun