Tree of heaven (Ailanthus altissima) - Early Detection Species

patch of spotted knapweed plants with pink/purple flowers

 
 

Tree of heaven is a tree that is a well-known invasive species problem in the eastern United States, but has only been found in Minnesota in limited numbers. Tree of heaven can form dense stands that hinder forest regeneration and the plant is a host of the agricultural pest spotted lanternfly. In Minnesota, tree of heaven is a prohibited noxious weed on the eradicate list so any trees found must be killed.

Warning: Cases of skin irritation have been reported. Avoid contact with plant parts such as leaves and sap. Tree of heaven pollen can also be allergenic for some people.

Description

Appearance

Tree of heaven is a tree that can grow rapidly and reach 50-90 feet tall. Plants have large leaves made up of many smaller leaflets and may be mistaken for trees such as walnut. Tree of heaven has separate male and female plants, so not all plants can produce seeds.

Leaves and Stem

The leaves are arranged on stems such that they alternate which side of the stem each leaf grows on. The leaves are large and made up of 11-41 smaller leaflets. The leaves are 1-4 feet long and the individual leaflets are 3-5 inches long. The leaflets have smooth edges, two lobes at the base of the leaflet, and a small stalk.

Mature tree of heaven bark is gray and bumpy. Tree of heaven twigs have a spongy brown center (pith).

Flowers

Flowers are small with five yellow-green petals. Flowers occur in clusters on the plant. Usually, male and female flowers are on separate plants, but plants that have both male and female flowers or individual flowers that have both male and female parts have been reported. The male flowers have stamens that release pollen and the female flowers have a stigma that collects pollen. Flowers bloom in June.

Seeds and Reproductive Structures

Tree of heaven produces one seed per seedpod. The seedpods start out greenish-red and mature to brown. Seedpods are dispersed by wind.
Trees can also spread vegetatively by sending up root suckers up to 50 feet away from the parent plant.

Roots

Trees can send up root suckers up to 50 feet away from the parent plant.

Biology

Tree of heaven is perennial tree or shrub. A mature tree can produce up to 325,000 seeds per year. It can also spread by root suckers to form dense patches of plants. It can grow in full sun to partial shade and tolerate many types of habitats including urban areas, roadsides, and other areas without dense tree cover.

Origin and Spread

Tree of heaven is native to Asia. It was planted in the United States as a landscape and boulevard tree. There have been few reported trees in Minnesota.

Refer to EDDMapS Distribution Maps for current distribution.

Don't be fooled by these look-alikes

  • Smooth sumac, Rhus glabra (native) and staghorn sumac, Rhus typhina (native) – the leaflets of the sumacs are serrated while the leaflets of tree of heaven are smooth except for the two lobes at the base.
  • Black walnut, Juglans nigra (native) – the leaflets of black walnut have fine serrations while the leaflets while tree of heaven are smooth except for the two lobes at the base.
  • Butternut, Juglans cinerea (native) – the leaflets of butternut have fine serrations while the leaflets while tree of heaven are smooth except for the two lobes at the base.
  • Amur cork tree, Phellodendron amurense (non-native) – Amur cork tree leaves are opposite (they come off the twig in pairs) while tree of heaven leaves are alternate (one at a time).
 
Regulatory Classification

Tree of heaven is a Minnesota Department of Agriculture Prohibited Noxious Weed on the Eradicate List meaning that the above and belowground parts of the plant must be destroyed. Additionally no transportation, propagation, or sale is allowed.

Threat to Minnesota
  • Tree of heaven can outcompete native species by forming dense cover and releasing allelochemicals that inhibit growth of other plants.
  • It can impede reforestation of desired trees.
  • It is a host for the invasive spotted lanternfly that has been found in the eastern United States and damages trees and is a threat to agricultural fruit crops. The Minnesota Department of Agriculture spotted lanternfly webpage has information for Minnesota.
  • Tree of heaven can have human health impacts. Cases of skin irritation have been reported. Avoid contact with plant parts such as leaves and sap. Tree of heaven pollen can also be allergenic for some people.
What you should do

One way that invasive plant seeds and fragments can spread is in soil. Sometimes plants are planted purposefully. You can prevent the spread of invasive plants.

PlayCleanGo: Stop Invasive Species in Your Tracks

  • REMOVE plants, animals & mud from boots, gear, pets & vehicle.
  • CLEAN your gear before entering & leaving the recreation site.
  • STAY on designated roads & trails.
  • PLANT non-invasive species.
Native Substitutes
 
Control Methods

Mechanical controlcan be done by digging or pulling small plants.

Herbicide control can be done using systemic herbicides, which are taken up by plants and move within the plant, killing leaves, stems, and roots. Cut plants will resprout if the stump is not treated with herbicide after cutting. Immediately after cutting (within 2 hours), apply an herbicide containing triclopyr (Garlon 3A/Vastlan, Garlon 4, or other brush killers with triclopyr) or glyphosate (Roundup) to the cut stump to prevent re-sprouting. Always follow label instructions for herbicides. Herbicides can be applied to cut stumps with a paintbrush, wick applicator such as a dauber or "buckthorn blaster," or a low volume sprayer.

In cases where more than a few plants are treated, add an indicator dye (available where pesticides are sold), such as Mark-It Blue, to the herbicide to mark which cut stumps you have sprayed.

For basal stem treatment, a method that applies chemical through the bark, low volume spray applications can be made with Garlon 4, Pathfinder II and similar oil-based products. This application method uses triclopyr ester mixed with an oil diluent (i.e. Bark Oil Blue, kerosene) applied directly to the bark of tree of heaven from the root collar up about 12-18 inches. An ultra-low volume spray wand should be used to minimize herbicide use and reduce the potential for non-target injury.

Reporting
Resources