ILANTHUS (Tree of Heaven) Simarubaceae A. altissima
HABITAT: Native to India, China. Zone 4.
USES: City tree under adverse conditions, parks.
HABIT: Tall to 60', hardy fast growing, deciduous trees with large, alternate, compound, fern-shaped leaves and bearing small yellow, vile smelling flowers (male trees) in late June and large clusters of "keys" (female trees) similar to maples except seed is in the center of the wing. The green leaves are reddish as they unfurl in early spring and are 1-3' in length with each consisting of 11-21 leaflets which grow in bunches at the end of the heavy twigs. The Ailanthus withstands trying city conditions and withstands seashore plantings. Fruits are produced which turn reddish in late summer.
SEED GERMINATION AND CULTURE: Place seed in a plastic bag with moist Grow Mix in the bottom of the refrigerator for two months and then remove and sow in flats of moist Park's Grow Mix, covering lightly and maintaining both moisture and a 70° temperature during the germination period. Seeds may be erratic in germinating and may require a month or more to do so. Transplant when large enough to handle to 2 1/4" peat pots then shift to 4" peat pots when the roots emerge from pot walls and grow on in a protected (Cold Frame) spot until seedlings are large enough to shift to permanent spots.
Place female trees (odorless and unable to produce seedlings without male trees) in the spring or fall in most any type of soil and in the sun or shaded areas.
Feed in the spring with a 10-10-10 fertilizer at the rate of 2 lbs. per 1" of trunk diameter. Punch holes in soil around the tree 18-24" apart and 12-18" deep, placing holes at the drip line (2/3 of the distance from the trunk to the outer edge of the leaf line). Keep sprayed for insects and diseases.
Underground shoots should be pruned as soon as they appear and prune above ground wood only if needed during the winter.
INSECTS: Not generally a problem.
DISEASES: Verticillium Wilt: Destroy infected plants. No known chemical control.
PROPAGATION: Grafts, root cuttings, seeds.