Tree-of-heaven is a medium-sized tree, with a broad, rounded crown. The tree has a tropical appearance.Read more about Tree, Bark, Twigs
Leaves are long and pinnately compound with 11 - 41 tapered leaflets, each with a tooth at either side of the base.Read more about Leaves
Flowers are yellowish-green, borne in erect clusters at the tips of branches.Read more about Flowers
Fruits are twisted samaras (winged seeds) borne in clusters. They mature from green to reddish- or yellowish-brown.Read more about Fruit
Tree-of-heaven is a medium-sized tree, up to 25 m (82') in height and 75 cm (2' 5) in diameter. The crown is rounded, broad and not too dense. The tree has a tropical appearance.
Winter twigs have prominent heart-shaped leaf scars and small, round buds, each with 2 - 4 brown hairy scales.
Leaves are pinnately compound with 11 - 41 leaflets on a central stalk that is 25 - 75 cm (10" - 30") long. They emit an unpleasant odour when crushed.
Each leaflet is 5 - 15 cm (2" - 6") long, tapered at the tip, widest toward the base. There is a nubby tooth at either side of the base and a warty gland on the underside of this tooth.
Yellowish-green flowers are borne in erect clusters, 10 - 30 cm (4" - 12") long. Male and female flowers are usually borne on separate trees.
Male and female flowers are similar in appearance, about 5 mm (1/5") across, with 5 petals. Male (pollen) flowers have an unpleasant odour.
Tree-of-heaven's ability to survive in harsh conditions provided the inspiration for Betty Smith's novel 'A Tree Grows in Brooklyn,' about a girl's coming of age in Brooklyn.
Tree-of-heaven is native to China. It was brought from there to England by Jesuit missionaries in 1751 and was subsequently exported to North America, first to Philadelphia, in 1784. Tree-of-heaven was also introduced to California by Chinese miners during the gold rush in the 19th Century. Tree-of-heaven now grows wild from Canada to Argentina.
Biology and Habit
Tree-of-heaven is a hardy, fast-growing invasive species capable of out-competing native species, and thriving in the most inhospitable conditions. It has reportedly been able to grow from root sprouts up to 46m (150') away from the parent tree. It can take root in cracks in the pavement and can withstand pollution, drought, and poor soil. It also secretes toxic compounds that suppress competing plant growth.
Derivation of names
The genus name, Ailanthus, derives from the Indonesian name ailanthos, which means "tree of heaven," or "tree reaching-for-the-sky", a reference to the speed with which trees in this genus grow. The species name, altissima, is from the Latin for very high or highest. When first brought to the west, it was assumed tree-of-heaven was a sumac (Rhus, which has similar compound leaves); however, it was correctly identified as Ailanthus when specimens with fruit were seen. The alternative common name Chinese sumac is also applied to Rhus chinensis. Tree-of-heaven is also called "stinking ash" in reference to the unpleasant odour emitted by its leaf glands when they are rubbed.
Tree-of-heaven's place in Toronto's urban forest
Tree-of-heaven populates a variety of disturbed areas in the city, including alleys, railyards, vacant lots, fence-lines, and cracks in the sidewalk. It is a very fast-growing species capable of 2 m of growth per growing season when the tree is young. It is highly resistant to pollution and urban stresses.
Landscape value and potential for home planting
Tree-of-heaven is one of the most invasive plants in North America and, as such, is not recommended for planting. Once established it is very hard to eradicate (the best solution is to weed out seedlings when they first pop up).
Because of the male tree's unpleasant-smelling flowers, female trees have usually been planted. However, this does not prevent the tree from reproducing, as it can also grow from root sprouts.
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