Last week's featured plant was one of the smallest trees that grows naturally in the Illawarra, so this week I can't resist looking at one of the largest, and also one of my absolute favourites: the Blackbutt (Eucalyptus pilularis).

This is the massive tall eucalypt that naturally dominates along the spurs of the escarpment foothills. While much of the Blackbutt forest in the region has been cleared, there are still many areas remaining.

A good place to see Blackbutts is around the housing in suburban areas on the escarpment north from Mount Keira. For example, huge trees surround the pole homes in western Bulli. There are also a few streets in Mangerton that are lined with magnificent specimens, creating a beautiful shady canopy.  

Many people find large eucalypts a bit confronting, particularly in urban areas, due to their association with risks of fire and falling limbs. These associations tend to overstate the risks (as this powerful and informative article from Dr Dean Nicolle makes clear).

Eucalypts are vital elements in local ecosystems, and a mature Blackbutt provides food and shelter to hundreds of different species of bird, insect and mammal, from tiny jewel bugs and aphids to grey-headed flying foxes, possums and gliders, and Powerful Owls. The Blackbutts behind our place in Mount Pleasant have hollows inhabited by sugar gliders and feather-tailed gliders, not to mention all the assorted parrots.

This species only starts to form suitable hollows for small mammals at about 100 years of age, and big hollows for King Parrots,Yellow-tailed Black Cockatoos and other larger birds from 200 years.

It's actually the same processes that produce falling branches and hollow trunks that create safe nesting places for native fauna, such as when termites eat away a tree's heartwood and leave suitable cavities behind.

While Blackbutts don't make comfortable bedfellows in typical urban gardens, their incredible biodiversity contribution means it's important to respect and protect them in natural areas and where they're still present as street trees.         

Emma Rooksby is the co-ordinator of the Growing Illawarra Natives website