Tuesday, October 2, 2007

Heaven on Earth?

Tuesdays are devoted to discussions about weeds, including any number of exotic invasives.

We see them all the time and don't even know it. They look a lot like sumac, but don't turn red in the fall. They grow quickly and can take over native trees in a very short period of time. And guess what? They are hard to get rid of. Another Exotic Invasive. This one is called Ailantheus or Tree of Heaven. You can even order it from some nursery catalogs. No. Don't do it. If you really want some, I'll give you plenty, but your neighbors might not be very pleased.

This tree is very commonly seen along the highway and will colonize recently cleared places. It's leaves look very much like sumac. Its rapid growth and spread can be attributed to a couple factors.

Ailantheus can spread through seed or through suckers. The suckering is it's secret to rapid establishment. When cut, the stump will send up suckers almost immediately. That way if the plant doesn't get a chance to seed, it will still spread.

If you start to cut it or dig it out, you will immediately notice a rather pungent not so pleasant odor. This is also a secret to success. The scent that repels you, repels the local plants as well and prevents other native trees from establishing themselves. Sumac does not smell the same.

Ailantheus also grows quickly, often reaching 10-20 feet within a year or two. Once the weather gets moderately warm, it's growing. Its height shades out other slower growing and not as tall species. This is one of the ways you can tell it from sumac. Sumacs tend to branch closely to the ground, while alantheus will often have a cluster of leaves and small branches at the very top of the tree. There will not be any lower branches. The tree's energy is put into gaining height. This is one of the reasons for its name.

Alantheus trees are native to southeast Asia and do not seem to have natural predators here in the southeastern United States. I did notice this year that the freeze in April, did them in quite nicely and it took them quite a while to recover. Eventually they did, but their growth was not as exuberant as it was last year.

To get rid of these pests, you will have to cut and dig them out. You can spray them with a strong chemical if that's your thing, but then you have the chemical hanging around to deter native plants. I think that watching the weather and cutting them back right before a cold snap in the spring will be the best way to slow their growth. Then if you can put in some more vigorous native species, like sumac, you can limit the Tree of Heaven that year. Like most invasives, it will take sustained effort over a number of years on your part to eradicate. And that is even if you use chemicals. Be patient and persistent, just like an exotic invasive. Only you belong here.
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