To control tree of heaven, use Yates Tree & Blackberry Killer. For seedlings up to 5 cm diameter, apply Yates Tree & Blackberry Killer as a basal bark spray. For treatment of suckers and seedlings more than 5 cm in diameter, apply as a cut stump treatment. For both treatments, you will need to mix Yates Tree & Blackberry Killer with kerosene. Please read label instructions on the back of the bottle for more information.
Continue to monitor the area(s) after treatment as there are likely to be seeds germinating or suckers appearing, especially if there is any soil disturbance, such as cultivation or changes in soil moisture.
Tree of heaven is an invasive woody tree that is widespread across most of Australia. Native to Taiwan and China, tree of heaven was introduced to Australia in the mid-1800s as an ornamental garden plant and shade tree. However, it soon escaped homesteads and naturalised in nearby bushland and pastures. Tree of heaven spreads easily via seeds and suckers, allowing it to grow into dense thickets that can exclude other vegetation.
This deciduous tree grows between 10–20 m tall with large compound leaves (multiple leaflets attached to a single rachis or stem) that can grow up to 1 m long. The dark green leaflets are arranged in pairs, with up to 20 leaflet pairs on one leaf. Each leaflet has a distinctive tooth-like bump at the base of the leaf. In autumn, the leaves turn yellow and fall, but appear again in early spring; emerging as bronze-coloured leaflets before turning dark green. Clusters of small, white, or yellow-green flowers appear at the ends of branches from late spring to summer. Male and female flowers are borne on separate plants (dioecious) although some plants may have both. The male flowers release an odorous smell to attract insects to assist with pollination.
Flattened winged yellow-brown fruits appear (40–50 mm long) and age reddish-pink or red-brown. Each fruit encases a single seed, and an established mature tree can produce up to 300,000 seeds annually. The winged fruit are easily dispersed by wind or water and will germinate readily in a range of soil types and light conditions. Seeds germinate in spring and form extensive root systems within the first year.
Tree of heaven is a particularly aggressive weed as its seeds can suppress the germination of other seeds – they contain toxins that can inhibit growth (allelopathy). Once established, it also suckers profusely and will easily re-grow from root segments. Trees that are simply cut down will sucker and spread, so proper control is required to manage this invasive weed.
Due to its aggressive nature, it has been known to form dense monocultures, completely excluding other species and consequently, displacing plant communities.