You don’t have to plant eucalypts

On Black Saturday in 2009 – the hottest day ever recorded in Victoria at 46°C – we were hiking in Tasmania, oblivious to the catastrophe unfolding because we were walking in a temperature of just 26°C.

When we came back into phone range, a close friend sent pictures of the bushfires that totally destroyed his house and farm.

We learned later when we visited that it was the oak trees that survived, along with all of his fruit trees. In short, the flammable ‘eucalyptics’ were burnt and the deciduous trees survived.

Could it be that flammability is actually a stratagem to defeat the competition? After burning they re-sprout from the lignotuber and spread their seeds in the fertile ashes to beat the competition and dominate the sunlight.

If we are to replace eucalypts in our gardens due to fire risks and because they provide lousy shade, which trees should we choose?

Visit our world-class botanic gardens for guidance

We are incredibly fortunate because our English heritage encouraged the establishment of five incredibly important botanic gardens located in Brisbane, Sydney, Melbourne, Hobart and Adelaide.

In these gardens we have at least 175 years of trialling to guide us, from mature deciduous trees to plantings of native trees (non-‘eucalyptic’) from our rainforests. I have been visiting these botanic gardens now for more than 20 years to find the toughest natives that will grow quickly, provide excellent shade and enhance our sense of beauty.

Drought tolerance and survival

In Adelaide, which is hotter and drier than other cities, we are fortunate to have the Waite Institute arboretum, which was established nearly 100 years ago, just 10km away from the CBD. This enables us to evaluate growth patterns and the impacts of hot, dry conditions on drought tolerance and survival. We can compare the growth rates and heights of the trees at Waite, which are grown naturally and without any additional attention, to the very same trees in the botanic gardens, where they grow under ideal cultivation, watering and husbandry.

Fast-growing non-flammable evergreens

Native evergreens from our rainforests

In our valley at Heronswood we have had exciting results with growth rates of our native rainforest trees – Kauri Pine, Bunya Pine, Hill’s Fig, Black Booyong and Red Cedar – in unwatered and unimproved soil. In planting the trees we have incorporated the spent trunks of banana, Musa ensete, which has generated phenomenal growth, particularly with the Flame tree, Brachychiton acerifolius.

Oaks

Our early settlers brought out oak seeds so we now have over 100 years of growing experience and some truly huge trees are growing in southern states. Of particular significance is the oak lawn at Melbourne’s Royal Botanic Gardens. Two of the largest and fastest growing oaks are specimens of Quercus canariensis, whose broad canopies provide generous shade for garden visitors. All oaks start life with deep tap roots so they forage for moisture faster than most trees, and even deciduous oaks survive drought as efficiently as the evergreen Holm and Cork oaks

To produce long-lived oaks it is vital that you prune forks in trunks early, as well as large side branches that exceed pencil thickness. A forked oak will often split in a storm or during lightning strikes so, if your oaks are forked, you may need to provide cable support between the thickest branches.

At the Blazey Arboretum we are currently planting all the rainforest natives mentioned above, as well as about ten oak species