Budding myth. (journal extracts).

EUCALYPTS are famous for their ability to sprout new shoots along their branches and stems after fire, insect attack, drought, lopping or wind damage. Anyone who has heard of these epicormic shoots knows that they sprout from small dormant buds buried in the outer bark of the tree. `Wrong!' says Dr Geoff Burrows of Charles Sturt University. It now seems that this long-standing belief, even among botanists and foresters, is a myth.

After studying the anatomy of epicormic bud strands in the sugar gum (Eucalyptus cladocalyx), and in other related species, Burrows says that typically no buds are present in the stems or larger branches of eucalypts. Rather, these trees have radially orientated strands of tissue, which extend from the pith, or inner core of the stem, to the outer bark. Close inspection of a smooth-barked species of eucalypt, such as a sugar gum or ribbon gum, will reveal little mounds on the surface of its branches, indicating the location of the tips of these strands. In the inner bark, near the wood, each strand possesses several very narrow strips of cells that can produce hundreds of buds, but only when given the appropriate hormonal signal, say after fire.

In many northern hemisphere trees, such as oak, maple and willows, epicormic shoots grow from small, but fully formed, buds embedded in the outer bark. However, in our eucalypts the epicormic buds tend to form, only when required, from tissues close to the wood, where they gain maximum protection thanks to the full thickness of the bark. This is one reason why eucalypts are very fire resistant. In contrast, the dormant buds of many exotic trees could easily be damaged by fire.

Burrows GE (2000) An anatomical study of epicormic bud strand structure in Eucalyptus cladocalyx (Myrtaceae). Australian Journal of Botany, 48:233-245.