Ailanthus ALTISSIMA

Ailanthus ALTISSIMA - Tree of Heaven, Ailanthus altissima, Paradise Tree, Chinese Sumac.

Ailanthus is a genus in the quassia family (Simaroubaceae), comprising about ten species of trees. They grow in East and Southeast Asia and in Australia.

The trees are deciduous, fast-growing, with smooth grayish bark and very large odd-pinnate leaves. The wood is soft, lightweight, and of low commercial value.

The plants are dioecious; the flowers are small, greenish-yellow, gathered in large terminal panicles. The fruit is a flat samara with a seed in the center, clustered in showy drooping bunches that turn red by autumn.

Tree of heaven is a tree up to 25-30 m (82-98 ft) tall native to northern and central China. The epithet "altissima" ("highest") was given for its growth rate: in its early years, a sapling rises 2-3 m (6.6-9.8 ft) per season.

The leaves are up to 60-90 cm (24-35 in) long, consisting of 13-25 leaflets, with a reddish tinge upon unfolding. Male flowers emit a sharp unpleasant odor, while female ones are almost odorless. In autumn, the tree is draped with clusters of reddish-ochre samaras that persist until winter and are highly ornamental.

Ailanthus seeds are flat samaras; germination rates are high and maintained for 2-3 years. The wing is not removed before sowing. Seeds are soaked for 12-24 hours in warm water or in a solution of growth stimulant: SUPERthrive, HB-101, Aminosol, Epin, or Zircon. Stratification is desirable: 1-2 months at 2-5 °C (36-41 °F) in moist sand noticeably evens out germination.

Sowing is carried out in spring into loose substrate to a depth of 1-2 cm (0.4-0.8 in) or before winter directly into open ground. The sowing is moistened with a spray mister and germinated in the light at a temperature of 18-25 °C (64-77 °F).

Seedlings appear after 2-4 weeks, uniformly. Seedlings grow very rapidly and reach one meter (3.3 ft) during the first season, so pricking out into individual deep pots is carried out immediately after the unfurling of the first pair of true leaves.

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Any bright spot suits the plant, preferably full sun.

The species is cold-hardy, enduring temperate zone frosts without shelter. It is beneficial to mulch young seedlings for their first winter.

Watering is moderate, only for young plants. A mature tree is drought-tolerant and practically requires no watering.

Any substrate is suitable: ailanthus tolerates poor, saline, and compacted soil alike. In container cultivation, drainage is placed at the bottom of the pot.

Feeding is not required; the tree grows excellently without it. An excess of nutrients only intensifies its already vigorous growth.

Ailanthus tolerates pruning excellently, and after it produces vigorous shoots with especially large leaves. When planting in open ground, one should remember its abundant root suckering and plant the tree away from lawns and flowerbeds.

Special notes: The sap and fresh bark of ailanthus contain irritating substances and cause dermatitis in sensitive individuals, so pruning is best performed wearing gloves. In open ground, the tree aggressively spreads via root suckers and self-seeding; in a small garden, it is safer to keep it in a container.