Which tree is best for your small garden? It depends on where you live

That old Chinese proverb “The best time to plant a tree is 20 years ago; and the second best is now” is not actually Chinese. But that doesn’t mean it’s not true, both metaphorically and literally. In the era of climate change, the proverb acquires a new urgency: you can’t plant a tree soon enough. And winter is tree-planting season. Deciduous trees are dormant and evergreen trees have slowed their growth, making transplant less risky for both.

The critical question, though, is not when or where: the City of Sydney’s latest planning document for greening the city advises that just 20 square metres is a big enough space for a small tree. And it certainly isn’t why: the good reasons for tree-planting range from aesthetic beauty, climate mitigation and physical and mental health benefits to cold hard cash; house prices rise with rising tree canopy.

The vital question is which tree? Trees planted today will mature in about 2040 and can be expected to live until at least 2070, so it’s crucial that the species chosen today are resilient to the coming climate.

The Which Plant Where project, a collaboration between teams from Macquarie University, Western Sydney University, Hort Innovation Australia and the NSW Department of Planning, Industry and Environment, aims to identify the most appropriate plant species for our urban landscapes into the future. Researchers have been assessing the impact of different environmental stressors on different species in different places.

Which Plant Where will be an online tool (going live this spring) that allows gardeners to make climate-resilient choices. The information will also help nurserypeople to propagate future-proof plant material, making plants available that aren’t now in garden centres.

Trees planted today will mature in about 2040 and can be expected to live until at least 2070.

But if you plan to make the most of lockdown makeover opportunities during tree-planting season, or to celebrate National Tree Day on August 1 by planting a tree, you need the information now. Fortunately, Which Plant Where is keen to share.

The researchers have found that based on climate suitability for 2030, 2040 and 2070, one of the small tree options for gardens in the western suburbs is the macadamia, which can be pruned to about 4m high and wide, has high drought and frost tolerance and gorgeous trusses of cream flowers. Not to mention the nuts. With a bit more space, try the leopardwood, Flindersia maculosa, which gets its common name for the beautifully spotted trunk. It also has ferny leaves a little like a jacaranda and yellow flowers in summer.

Gardens in the east in need of a small tree could consider a coral tree, Erythrina speciosa, which flowers in winter on bare wood with vivid red blooms, or the elegant Chinese dogwood, Cornus kousa. Both are deciduous, so offer shade in summer and sun in winter. For year-round canopy cover, the options include citrus trees and the east coast rainforest tree known as steelwood, Sarcopteryx stipata. But that last one might be hard to find – at least for now.