Iconic Eucalypts

Iconic Eucalypts

Thoughts of Australia are associated with our dominant group of trees – the eucalypts. This diverse group is most characteristic of dry forests, but are also a major component of wet forests, are found in semi-arid regions and on mountain tops. They flourish in dry and wet places, on exposed sites and in sheltered valleys. Each is adapted to its particular environment, but all share hard leaves (a response to relatively low water and poor soil phosphate levels) and the ability to regenerate from dormant buds after all but the most severe fires. During the course of time, a large number of animals have co-evolved with these trees and when we lose eucalypts to land clearing we lose a diverse group of significant fauna.

Most eucalypts are too large for the modern, smaller garden. The heavily flowering Plunkett mallee (Eucalyptus curtisii) is a dense, multi-stemmed shrub to 6m. Although reaching 20m at maturity, the Moreton Bay ash (Corymbia tessellaris) is a slow growing, slender tree with a delicate canopy (picured). Branches rarely fall from this species. Larger species definitely deserve serious consideration by those living on large blocks and acreage or who wish to regenerate despoiled land. Plantings in home gardens should be on the south side of any building to minimize the effect of shade on shrubs and ground cover that need sunlight for flowering and at least 5m from pipes or concrete foundations. An effective way to increase fauna diversity and maintain good understory planting is to group several trees within 1.5 – 2.5m from each other so that their merging crowns will not create excessive shade.

The narrow-leafed ironbark (Eucalyptus crebra) is a common tree of the lower, well drained slopes around Brisbane where it grows to about 25m (its specific name -crebra -means abundant). The timber, as with other ironbarks, is dark, very hard, dense, strong and durable and is favoured for fencing and railway sleepers. The white, terminal flowers are abundant from May to November and attract bees. Koalas feed on the young leaves and sugar gliders feed on both the sap and insects attracted to the tree.

Eucalyptus grandis, Eucalyptus crebra – Photographs courtesy of Neil Murphy.

The smooth fruited grey gum (Eucalyptus propinqua) is another medium sized tree growing to about 30m. It has smooth, grey bark that is shed annually in flakes to expose the new orange bark that contrasts with the leaves that are dark green above and paler below. White flowers are borne terminally from January to March and attract bees and adult butterflies as well as nectar feeding birds such as the lorikeets, parrots and honeyeaters. Insect eating birds (e.g. cuckoos, the rainbow bee-eater, dollar bird and tree creepers) are drawn to insects feeding on nectar, leaves and sap. Koalas seek this out as a food tree. The yellow-bellied glider has a staple diet of nectar, pollen and sap (obtained by biting out small pieces of bark from the main branches) from this and other selected eucalypts, and insects. The greater glider feeds exclusively on the leaves.

Another koala host tree is the yellow box (Eucalyptus melliodora) that grows to about 20m. Its trunk is about half the tree height with a large, round crown of fine grey-green leaves. It has persistent, fibrous bark on the the lower trunk with inner yellow bark. Fallen branches make excellent firewood although the trees are forested for poles and heavy construction timber. It is regarded as the best honey tree of all the eucalypts and is a butterfly feeding tree. It is a significant tree for nectar and insect feeding birds.

These are but a few of the eucalypts, which can cater for small gardens through to large regeneration plantings, that are found at the nursery.

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