Master Gardener’s Corner: Tree-of-Heaven

Tree-of-heaven is an invasive weed. A tree of heaven it is not! It was initially valued as an urban street tree and was widely planted in the United States particularly around the Baltimore and Washington D.C. area.

Tree-of-heaven can reach heights of 80 feet and grow to 3 feet in diameter. The tree has smooth grey bark, stout, blunt, chestnut brown twigs, and a long compound leaf ranging in length from 1-4 feet with as many as 30 leaflets. The leaflets are smooth-edged except for 1-3 teeth near the base. Clusters of twisted papery seeds, called samaras, often hang on the trees over winter. The wood is soft, weak, course grained, and creamy white to light brown in color. All parts of the tree, especially the flowers, have a strong, offensive odor. Tree-of-heaven is often found growing in clusters as new shoots grow from the roots.

This species is easily confused with walnut trees. The foul odor produced by the crushed foliage and the scraped bark is also unique to tree-of-heaven.

Established trees constantly spread by sending up root suckers that may emerge as far as 50 feet from the parent tree allowing them to rapidly dominate sites.

Using only mechanical methods for controlling tree-of-heaven may be counter-productive since the tree responds to cutting and girdling by producing large numbers of stump sprouts and root suckers. Hand pulling of young seedlings may be effective when the soil is moist and the entire root system is removed. However, very small pieces of root are capable of generating new shoots.

The most effective approach for controlling tree-of-heaven includes the use of herbicides applied to foliage, stems, or cut surfaces. Persistence is the key to success.■

-—For more information go to ipm.ucanr.edu