Invasiveness Assessment - Tree of heaven (Ailanthus altissima) in Victoria

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Plant invasiveness is determined by evaluating a plant’s biological and ecological characteristics against criteria that encompass establishment requirements, growth rate and competitive ability, methods of reproduction, and dispersal mechanisms.

Each characteristic, or criterion, is assessed against a list of intensity ratings. Depending upon information found, a rating of Low, Medium Low, Medium High or High is assigned to that criterion. Where no data is available to answer a criterion, a rating of medium (M) is applied. A description of the invasiveness criteria and intensity ratings used in this process can be viewed here.

The following table provides information on the invasiveness of Tree of heaven.

A more detailed description of the methodology of the Victorian Weed Risk Assessment (WRA) method can be viewed below:

Victorian Weed Risk Assessment (WRA) method (PDF - 630 KB)
Victorian Weed Risk Assessment (WRA) method (DOC - 1026 KB)
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Common Name: Tree of heaven
Scientific name: Ailanthus altissima

Question	Comments	Reference	Rating
Establishment
Germination requirements?	Seeds germinate in spring. Roots sucker freely.	P & C (1992)	MH
Establishment requirements?	As a weed in dry sclerophyll forest and woodland, gullies and riparian areas, it is assumed to establish under moderate canopy and litter in these environments. “It survives without sun, water and seemingly earth”. (Shah 1997).	Carr et al (1992) P & C (1992)	H
How much disturbance is required?	Establishes in minor disturbed natural ecosystems – riparian vegetation, dry sclerophyll forest and woodland.	Carr et al (1992)	MH
Growth/Competitive
Life form?	Erect deciduous shrub. Other.	P & C (1992)	L
Allelopathic properties?	“Leaf extracts contain Allelopathic substances which adversely affect the growth of other plants”.	P & C (1992)	MH
Tolerates herb pressure?	Stock feed on lower leaves, so still capable of flowering under moderate herbivory.	P & C (1992)	MH
Normal growth rate?	As aggressive intruder that tends to displace indigenous flora.	Frankel (1999)	H
Stress tolerance to frost, drought, w/logg, sal. etc?	Tolerant of drought and saline soils. Occurs in areas prone to frosts (e.g. Austria, China, Ontario etc).	Bory et al (1991) CAB Abstracts	MH
Reproduction
Reproductive system	Reproducing from creeping roots and by seed.	P & C (1992)	H
Number of propagules produced?	Well over 2000 seeds on large tress. (see picture P & C 1992 p. 591).	P & C (1992)	H
Propagule longevity?	?		M
Reproductive period?	Can produce virtually pure stands remaining for long periods of time. Form thickets. Tress also known to survive > 35 years.	Rice (1984) - Cech (1998) Webb et al (1988)	H
Time to reproductive maturity?	Flowering does not occur until plants are > two years old. “It flowers during its second year of growth” . (APB 1992).	P & C (1992) APB (1992)	MH
Dispersal
Number of mechanisms?	Wind, water, birds, farm produce, machinery etc.	P & C (1992)	H
How far do they disperse?	Cultivation equipment, birds, and other mechanisms capable of dispersing propagules between 200-1,000 m.		H

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