Terrestrial Invasives

Ailanthus altissima

Ailanthus altissimaTree of heaven

Common Name 
Tree of heaven
Legal Status 
Target Species

A fast growing deciduous tree from China can grow 20m or more. It has smooth stems with pale gray bark, and twigs which are light chestnut brown, especially in the dormant season. In late spring, clusters of small, yellow-green flowers appear near the tips of branches. Seeds are produced on female trees in late summer to early autumn. Fruits are papery, somewhat twisted, winged structures called samaras that are tan to pink-coloured.

Where does this species come from? 
Northeastern and Central China and Taiwan
Why is it a problem? 
A common tree in urban areas where it causes damage to sewers and structures, Ailanthus poses a greater threat to agriculture and natural ecosystems. It is a vigorous growing tree and prolific seeder that establishes dense stands that push out natives. Tree of heaven contains chemicals, including ailanthone, that have been found to have strong allelopathic (herbicidal) effects on the growth of other plants which help it establish and spread.
Means of reproduction? 
Flowers, fruits and seeds: large showy clusters of small yellowish-green flowers produced during June; in summer, flat, twisted, single-seeded winged fruits or samaras are produced on female trees and may remain on trees for long periods of time; individual trees may produce an estimated 325,000 seeds per year.
Spreads: reproduces by seed and by vigorous re-sprouting, especially in response to injury such as breakage or cutting.