Chinese Tree of Heaven

I was in the southern Sierra Nevada mountains during November and I went for a hike along the Kern River. It was a beautiful fall day and many of the trees were displaying colorful foliage. I was surprised, however, when I noticed a Chinese Tree of Heaven (Ailanthus altissima) growing there by the river. Soon I recognized that it was growing everywhere and that there were thickets of it springing up throughout the riparian area.

The Chinese Tree of Heaven, as the name implies, comes from central China. It is a root sprouter and prolific seeder with a foul smell, and it can quickly take over any disturbed area. According to the Plant Conservation Alliance’s Alien Plant Working Group, the Tree of Heaven was first introduced in North America by a Philadelphia gardener in 1784. It has now spread to at least 30 states and has become an obnoxious pest.

This is something I know well, because in Salt Lake City we once bought a house with an established Tree of Heaven population. I was unfamiliar with the species at the time, but I soon determined that it was an unwelcome part of the landscape. It sprouted everywhere, pushing up into the garden, cracking the foundation, and leaning against the wall of the garage. I couldn’t stop it. I cut it, I dug it up, I sprayed it. After a while, my vigilance allowed me to stay even with it, but I hardly dared go away for a weekend vacation. After that experience, I will not consider buying any property where it has an established presence. It is that bad.

Because Ailanthus altissima is a stump and root sprouter, it will not go away when you cut it. That is, you can cut down the clump of trees, but the clump will immediately re-sprout from the cut stumps and lateral roots. According to The Nature Conservancy, there is not much information regarding the use of herbicides to control the pest, though it may be effective in some circumstances. In Salt Lake, the only thing that worked was heavy cutting, followed by persistent pulling of small sprouts and seedlings, but this level of maintenance is clearly impractical for an area a large as the Kern River Valley. In that case, it is likely that the locals will simply have to learn to live with the tree.

The Chinese Tree of Heaven is an alien plant in North America that is quickly becoming an invasive pest across the continent. It is a prolific seeder and sprouter and can quickly colonize an area. It is an ugly tree with a foul odor and poor form. The best way to remove it may be simply to persist in cutting it and weeding it over the long term. In my own experience, moreover, the tree is improperly named. I mean, if they've got these things in heaven, I'd rather go to the other place.