tree of heaven

Ailanthus altissima
habit in fruit (Photo: Land Protection, QDNRW)
habit in flower (Photo: Trevor James)
greyish bark on main trunk (Photo: Trevor James)
leaves (Photo: Sheldon Navie)
close-up of reddish-coloured young foliage (Photo: Trevor James)
close-up of leaflets with small lobes at their bases (Photo: Sheldon Navie)
close-up of the underside of the leaflets, showing the raised glands (Photo: Trevor James)
male flowers (Photo: Trevor James)
close-up of male flowers (Photo: Trevor James)
young fruit (Photo: Trevor James)
immature reddish-coloured fruit (Photo: Trevor James)
mature winged fruit (Photo: Trevor James)
seedling (Photo: Sheldon Navie)
Tree
Alternate
Compound
White
Yellow
Green

A large shrub or tree that loses its leaves during autumn. Its once-compound leaves are very large (40-100 cm long), with 5-20 pairs of leaflets and a single leaflet at the tip. Its leaflets are mostly entire, except for a few teeth or small lobes near the base which bear prominent raised glands. Its small white or greenish-yellow flowers are borne in large spreading clusters at the ends of the branches. Separate male and female flowers are produced on different plants. Its distinctive winged fruit (3-5 cm long and 7-15 mm wide) turn bright reddish-pink or reddish-brown as they mature.

Common names 
Also known as: ailanthus, baked sewage tree, China sum, tree of heaven,
Family 
Simaroubaceae
Deciduous 
Yes
Flowering time 
Late Spring-Summer
Native/Exotic 
Exotic
Origin 
Native to eastern Asia (i.e. north-eastern and central China).
Notifiable 
No
Council declaration 
SIL – Special Investigation List
Known distribution 

A widely naturalised species that is largely found throughout the coastal and sub-coastal regions of south-eastern Australia. It is most common in the coastal and sub-coastal regions of eastern New South Wales, in the ACT and in Victoria. Also relatively common or occasional in south-eastern South Australia, south-western Western Australia and south-eastern Queensland.

Habitat 

A weed of bushland, waterways, gullies, forest margins, pastures, forestry plantations, urban areas, abandoned homes, disturbed sites, waste areas, roadsides and railways in the humid and sub-humid temperate and sub-tropical regions of Australia.

Habit 

Rarely a large shrub or more commonly a medium to large tree that loses its leaves in autumn (i.e. it is deciduous). It usually grows from 3 to 12 m tall, but may occasionally reach up to 25 m in height.

Impact and control methods 

Tree of heaven (Ailanthus altissima) is regarded as an environmental weed in New South Wales, the ACT, Victoria, South Australia, Queensland and Western Australia. It was recently also listed as a priority environmental weed in two Natural Resource Management regions. This species primarily occurs in disturbed areas, but its winged seeds can blow considerable distances and it may also invade undisturbed habitats. It spreads into bushland from old homestead sites and other plantings, and is particularly invasive in riparian vegetation and along gullies. However, it can also invade dry sclerophyll forests and other woodlands. This species is an aggressive competitor due to its suppression of other plants with toxins (i.e. allelopathic chemicals) and the abundant suckers that it produces from its shallow roots. Tree of heaven (Ailanthus altissima) is also a very successful competitor for both light and nutrients, and typically shades out other species with its very large and dense leaves. The root suckers enable the plant to develop into extensive thickets, sometimes many hectares in size, that displace the native vegetation. These stands can be almost devoid of other species (i.e. monospecific) and can remain for long periods of time. It also re-sprouts vigorously when cut or damaged, making its eradication extremely difficult and time consuming.

Stem and leaves 

The leaf-bearing, younger stems are smooth or pitted, speckled and reddish-brown in colour. Mature stems have grey or yellowish-grey coloured bark that is slightly rough in texture. The stalked (i.e. petiolate) leaves are very large (40-100 cm long) and alternately arranged along the stems. These leaves are once-compound with 5-20 pairs of leaflets a single terminal leaflet (i.e. they are imparipinnate). Individual leaflets are narrowly oval (i.e. elliptic), egg-shaped in outline (i.e. ovate), or slightly elongated in shape and are borne on short stalks (i.e. petiolules). These leaflets (4-15 cm long and 1.5-6 cm wide) are hairless (i.e. glabrous) or sparsely hairy (i.e. puberulent). Their margins are mostly entire, except for a few teeth or a small lobe near the base of the leaflet, and their tips taper to a point (i.e. they have acuminate apices). There is one or more prominent raised glands on the underside of each leaflet, near the basal teeth or lobe. Leaves turn yellow and are lost during the autumn (i.e. it is deciduous), and new bright green leaves are produced in mid-spring.

Flowers and fruits 

The small flowers are borne in large spreading clusters (up to 60 cm long) at the tips of the branches (i.e. in terminal panicles). They are white or greenish-yellow in colour with five small petals (2-4 mm long), and five tiny sepals (i.e. calyx lobes) that are only 0.75-1 mm long. Separate male and female (i.e. unisexual) flowers are produced on different plants and the male flowers produce a very strong smell (i.e. they are very pungent). Flowering occurs during late spring and summer. The winged fruit (i.e. samara) are initially yellow or greenish in colour but turn reddish-pink or reddish-brown as they mature. These fruit consist of a rounded disc containing the seed (3-4 mm across) and a large flat wing (3-5 cm long and 7-15 mm wide). The fruit begin to develop in late summer and early autumn, but can remain on the tree into winter.

Reproduction and dispersal 

This plant reproduces by seed and also produces large numbers of suckers from its shallow roots, especially after the main stem is cut down. The seeds are mostly spread by wind and water, and these forms of dispersal are aided by their wings. They can also be dispersed by birds, machinery, mowers, and in dumped garden waste. Colonies also spread laterally over time, via the root suckers.

Similar species 

Tree of heaven (Ailanthus altissima) can sometimes be confused with rhus (Toxicodendron succedaneum). These species can be distinguished by the following differences: tree of heaven (Ailanthus altissima) has leaves that turn yellow in colour before they are shed. Its winged fruit (i.e. samaras) are relatively large (3-5 cm long) and turn reddish in colour as they mature.rhus (Toxicodendron succedaneum) has leaves that turn bright reddish in colour before they are shed. Its somewhat rounded berry-like fruit (i.e. drupes) are relatively small (5-10 mm across) and turn dark-brown in colour as they mature. Two native trees, red cedar (Toona ciliata) and pencil cedar (Polyscias murrayi), are also easily confused with tree of heaven (Ailanthus altissima) as they have very similar leaves. However, neither of these native trees have glands on the base of their leaflets, and pencil cedar (Polyscias murrayi) does not lose its leaves during autumn (i.e. it is evergreen). Also, the fruit of red cedar (Toona ciliata) is a dry capsule (1-2 cm long) which splits open to release four or five winged seeds, while the fruit of pencil cedar (Polyscias murrayi) is a small purple 'berry' (i.e. drupe) about 4 mm across.