Tree of Heaven: Control Strategies (2024)

The rapidly growing, invasive tree-of-heaven is difficult to eliminate due to its prolific seed production and root suckering ability. To control tree-of-heaven, you must control the roots. Learn when and how to apply systemic herbicides to successfully eradicate the tree.

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- Tree-of-heaven, Ailanthus altissima, commonly referred to as ailanthus, is a rapidly growing, invasive tree found across much of the United States that aggressively reproduces by wind-dispersed seeds.

Female trees can produce more than 300,000 annually.

Once established, trees spread by root sprouts that can extend up to 50 feet away from the parent tree.

Root sprouts as young as two years of age can produce seeds.

Due to its extensive spreading root system and root suckering ability, tree-of-heaven is difficult to control.

However, if you follow the guidelines outlined here and are persistent, you can successfully eradicate it.

Mechanical methods such as cutting or mowing are ineffective at controlling tree-of-heaven.

In fact, cutting trees can make the situation worse as trees respond by sending up dozens of stump sprouts and root suckers.

Hand pulling young tree-of-heaven seedlings when the soil is moist can be effective.

However, it is often impractical to do so.

Here you see hundreds of seedlings that germinated in a small area.

For hand pulling to be effective, you must remove the entire root system.

Even small root fragments can generate new shoots.

Be aware that seedlings are easily confused with root suckers, which are nearly impossible to pull by hand.

To control tree-of-heaven you must control the root system.

The most effective way to do this is by applying a systemic herbicide at the optimum time of year.

Systemic herbicides must move through the tree's vascular system to the roots to be effective.

Therefore you need to apply the herbicide when the tree is moving sugars produced through photosynthesis down to the roots.

This is best accomplished in mid to late summer, July through September.

If you apply systemic herbicides to tree-of-heaven outside of this optimum time of year, you will injure above-ground growth, but you will not effectively control the roots.

In other words, the foliage may die but the roots will remain intact.

This is also why treative tree-of-heaven stumps with herbicides is not effective.

When you remove the top of the tree, you are removing the mechanism that moves the herbicide downward.

So the herbicide cannot effectively control the roots.

Stump treatment of tree-of-heaven will keep the stump from resprouting, but it will not prevent root suckering.

Before removing tree-of-heaven, treat them with a herbicide first.

Allow 30 days for it to take effect and then cut the tree.

There are many herbicides effective at controlling tree-of-heaven.

For most treatments, we recommend using herbicides containing the active ingredients glyphosate or triclopyr.

For up-to-date herbicide recommendations, refer to the Penn State Extension website.

Always follow the herbicide label instructions for rates, application methods, and personal protection.

There are three herbicide application methods effective at controlling tree-of-heaven: foliar, basal bark, and hack-and-squirt.

If trees are small and you can spray the leaves without contacting nearby desirable plants, you can use the foliar application method.

Foliar sprays are also good for initial treatment of dense or extensive infestations to eliminate small low growth.

Then follow up with a basal bark or hack-and-squirt application on remaining larger stems.

A mixture containing glyphosate and triclopyr is best for foliar treatments of tree-of-heaven.

You can apply foliar treatments using a low-volume backpack sprayer as shown here or with high-volume truck-mounted sprayers.

The basal bark application method is suitable for trees up to six inches in diameter.

The trees shown here are good candidates for this method.

This method is very selective so you can target tree-of-heaven without harming nearby plants.

Use a low-volume backpack sprayer containing a concentrated mixture of triclopyr ester and basal oil.

Apply the herbicide solution from the ground line to a height of 12 to 18 inches completely around the stem.

It's important that you treat completely around the stem so that the herbicide intercepts the complete vascular system to the roots.

The hack-and-squirt application method is another highly selective alternative for treating tree-of-heaven.

You can use it for trees one inch in diameter and larger.

To use this method, space downward-angled cuts, or hacks, evenly around the circumference of the tree and apply a herbicide solution to the cuts.

You can use formulations of either glyphosate or triclopyr amine.

By intentionally leaving uncut tissue between the hacks, you provide open pathways for the herbicide to move to the roots.

Use a hatchet with a narrow blade to make the cuts in the tree.

To create a more effective hack-and-squirt tool, you can modify a regular hatchet by grinding down the blade so that it's no more than two inches wide.

This modified hatchet will create a narrow cut to better hold the herbicide.

The rule of thumb for hack-and-squirt applications is to make one cut per inch of tree diameter with a minimum of two on small stems.

For a six-inch diameter tree, make six cuts evenly spaced around the circumference of the tree with intact bark left between each.

Then fill each cut with herbicide solution.

Again, be sure to apply all herbicide treatments in mid to late summer to maximize herbicide movement to roots.

After the initial treatment, monitor the site for signs of regrowth and retreat as necessary.

Initial treatments often only reduce the root systems, making follow-up measures essential.

This is critical to prevent reinfestation.

Well-established tree-of-heaven stands are only eliminated through repeated efforts.

Persistence is the key to success.