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Ailanthus altissima

Biological Category 
Plants
Species Type 
Tree
NY Invasiveness Rank 
Moderate
LHPrism Status 
Tier 4 - Widespread

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Description 
  • Tree of heaven is a member of the Tree of heaven family (Simaroubaceae)
  • A rapidly growing deciduous tree native to China, tree of heaven can grow to over 60 feet in height. The species’ branches are very brittle and easily broken, and its bark light grey, and smooth. (4)

Leaves
Leaves are large, up to 3 feet long, compound and composed of 11-25 leaflets. The leaflets have a pair of prominent glands on the underside and are malodorous when crushed. Generally, one or more coarse teeth are present at the base of each leaflet. (3)

Flowers
Flowers develop into pale, papery samaras turning tan to reddish to pink as summer progresses into fall. (3)

Introduction History 
Introduced via the horticultural trade in the mid-1700s, tree of heaven was prized for its exotic foliage. Planted heavily throughout cities it was renowned as a near indestructible street tree and touted for its tolerance of soil compaction and pollution. (2)
Ecology and Habitat 
Tree of heaven is tolerant of a variety of soil types in full sun to shade. The species is strongly associated with anthropogenic disturbance and is commonly found in waste places such as roadsides, parking lots, and old fields. The species also favors naturally occurring early successional habitats. (2)
Reproduction and Phenology 
Tree of heaven is a prolific reproducer, capable of producing over a million seeds per mature tree in optimum conditions. (7) Although most of these seeds fall within 20 feet of the parent tree, Tree of heaven rivals Ash (Fraxinus) as one of the furthest wind-dispersing trees in the New York canopy. Although seed rain from this invasive species is heavy, Tree of heaven is short lived, and its productive years shorter still: most trees live less than 100 years, with their most fecund years taking place early in their lifespan. Additionally, the species does not appear to build up a persistent seed bank, and most seeds live only one year in the soil. (8) Tree of heaven does reproduce vegetatively, however, and these ramets can increase the lifespan of a single individual by hundreds of years. (4) Vectors include wind and water (4)
Impacts of this species 

Tree of heaven has a moderate impact on the ecological communities it invades: little evidence exists to suggest it alters natural environmental processes and the species has no native congeners with which to hybridize. Established stands of this invasive tree can outcompete native species and change the composition and density of the surrounding vegetation, particularly in early successional habitats. (1) The species has been shown to exhibit allelopathic properties and can inhibit the germination and growth of other vegetation. (6)

Management Methods 

Biological Control
There is currently no single optimal biological control agent in use against this species. 

Manual or Mechanical Control
Pulling / Digging Up: Pulling by hand is an effective method of control for seedlings and small plants if the entire root is extracted from the soil. For larger plants this technique is not advisable as it will encourage root sprouting (4)

Mowing: Not advisable

Girdling: Girdling will top-kill larger trees, however, cut and stump treatment is safer and more effective. Tree of heaven is a very brittle tree: dead standing wood is incredibly hazardous due to its tendency to break apart and fall. (10)

Prescribed Fire: Not applicable. Tree of heaven has a long taproot, rendering it resistant to fire (4)

Prescribed Grazing: White tailed deer and goats will graze tree of heaven foliage, but it is not a preferred species. (4)

Soil Tilling: Not advisable. Tilling may fragment roots and encourage re-sprouting.

Mulching: Not applicable

Solarization: Not applicable

Hot Foam Spray: Not applicable

Chemical Control
The pesticide application rates and usage herein are recommendations based on research and interviews with land managers.  When considering the use of pesticides, it is your responsibility to fully understand the laws, regulations and best practices required to apply pesticides in a responsible manner.  At times, the pest you seek to treat may not be on a pesticide label, requiring a 2ee exemption from NYSDEC.  Always thoroughly read the label of any pesticide and consult the NYSDEC or a licensed pesticide applicator with questions.

Foliar Spray: A 2-3% solution of glyphosate or triclopyr is effective at managing small tree of heaven plants, although a repeat application may be necessary. Infestations managed in this way should be revisited in 2-3 weeks to monitor for regrowth. Always read and follow all instructions on the herbicide label. (10)

Cut Stump: Apply a 50% solution of glyphosate or triclopyr to the cut stump of larger tree of heaven plants towards the end of the growing season, but before leaf senescence. (12) 

Basal Bark: A 25% solution of triclopyr applied to the bark of dormant tree of heaven is somewhat effective in controlling infestations, although this technique is best applied with other strategies, such as a follow-up cut stump (12)

Hack-And-Squirt

Stem Injection: Picloram, Imazapyr and Triclopyr are all effective for stem injection use. Midsummer and late winter injections are most effective. Follow information on the product label for appropriate rates and instructions. (12)

Pre-Emergent Spray: Not applicable

Summary of Best Managment Practices 

General management overview and recommendation
As with any other invasive infestation complex, large stands of tree of heaven are best managed via a combination of mechanical and chemical means.  All managed infestations should be monitored for at least one year to ensure exhaustion of the seed bank. (4) Any new seedlings can be hand pulled. Even when using the most effective methods of chemical control, managed populations must be monitored due to the species’ strong tendency to form root sprouts. 

Post treatment monitoring
Any infestations managed by chemical means must be revisited in 2-3 weeks to check for treatment efficacy. Any infestations managed solely by mechanical means will need follow up treatment as soon as re-sprouts appear. Populations should be revisited the following year to ensure exhaustion of the short-lived seed bank. (10)

Disposal Methods
Waste material can be crushed, chipped, burned or composted so long as management was completed prior to seed set. Any fruit must be bagged and disposed of, and any roots thoroughly crushed or dried.