Experts tackle readers’ garden questions.
Q: Can you identify this plant that has invaded my yard? I have a drought tolerant type yard with most of it covered with landscape fabric, wood chips and gravel and a few plants on drip. This plant is invading under the weed block fabric and wood chips, pushing up these plants or little trees. In some places, it just grows under the fabric, staying white never greening up, in very dry hard dirt and just raises the fabric up, never actually breaking through. The leaves stink. I have pulled many feet of the root out and have been spraying with Bayer Brush Killer, which kills the plant but apparently not the root. There is no sign of a similar looking tree on either side of my lot. Any suggestions on how to eradicate it?
John Saylor, Citrus Heights
Bee garden writer Debbie Arrington: That’s a Tree of Heaven, although a better name would be Tree from Hell. In China, it’s known as chouchun, which means “foul smelling tree.” It’s a real stinker in more ways than one.
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A native of China, Tree of Heaven (Ailanthus altissima) has become an invasive pest in the U.S. It has the ability to put out amazing suckers, as you have seen. It’s considered among the fastest growing trees in California, often growing more than 6 feet per year. All parts of the plant have a distinctly strong odor similar to rotting cashews. The fragrance of the male flowers on these trees is especially stinky.
Tree of Heaven often grows where little else survives. In addition, Tree of Heaven releases a chemical compound that inhibits the growth of other plants. That gives it a big advantage over its competition. It’s very drought tolerant as well as tolerant of pollution and terrible growing conditions (such as poor soil or constant exposure to cement dust).
And it’s almost impossible to kill once it gets established.
According to the integrated pest management experts at the University of California cooperative extension, successful eradication needs a combination of methods of attack, both mechanical (chopping off the suckers and starving them of sunlight) and chemical (namely RoundUp or other glysophate compounds). When using RoundUp, paint it directly on the foliage of the suckers. That carries it down to the roots. Be careful of herbicide drift. (Roses for example are very sensitive to RoundUp, which can travel many feet in the air.)
From experience, I know diligence works. But you have to keep pulling out those suckers for a couple of years before they’re all gone – and that’s only if they’re not connected to a mother tree.
Your photos suggest the presence of another full-sized Tree of Heaven or a mature tree that no longer exists; that’s how all those suckers came to be so long and strong. If the mother tree is gone, the suckers will eventually run out of steam if you keep chopping off the re-sprouts.
For more information on how to deal with weedy trees or shrubs, click on the UC’s Integrated Pest Management website, ipm.ucanr.edu, and search for Pest Notes 74122.
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