Crooked River Farm has several patches of the dreaded Ailanthus tree, also known as Paradise Tree, Tree of Heaven, or locally called Shumace.
Ailanthus is one of the most dangerous trees in VA. Where it sprouts up, it sets out it’s own natural herbicide that keeps anything else much from coming up except itself. Female trees set tens of thousands of seeds each year, and it readily sprouts from its roots. Cut down an Ailanthus, and you’ll have hundreds of new trees sprout from the roots. So it needs special treatment to eradicate. It now lines our roadways all over VA as well as the edges of forests. VA Tech researchers have been working on biological control agents for several years to no avail.
There are no organic control/eradication techniques for Ailanthus, so here we parted from our organic approach and resorted to limited use of herbicide.
The common recommendation for Ailanthus eradication is to spray the leaves with herbicide. This of course is a bad idea, as there is no way to prevent the herbicide from drifting onto other plants. A common technique of killing undesirable trees and shrubs is to cut off the plant, and paint the stump with herbicide, but Ailanthus foils this technique by immediately sending up sprouts from the roots that don’t die after the host is killed.
So we tried a different technique. What we did was hack into the bark of the trunk with a machete (a hatchet will do) around the tree to expose the cambium layer and create a pocket for the herbicide. If you girdle the tree completely it will sprout from the roots and you’ll create a bigger problem, so the trick is to leave about 1″ of intact bark and cambium in between the hacks. Generally, you do one hack for every inch of tree diameter. And then in each hack, you squirt the herbicide to the point just before it will spill out of the hack. For sprouts less than 1″ in diameter, we’ve had 100% success with just exposing the cambium with a scrape and then squirting the scrape. The Ailanthus thinks it’s still alive while it absorbs the herbicide, and by the time it realizes it’s dying and tries to send up root sprouts, it’s too late.
This must be done while the tree is actively growing or it won’t work. This means from the time of first leaf-set up until the females are flowering. We “treated” trees after flowering, and they seemed to respond much more slowly and will have to wait until spring to see if they have been killed or not.
We just bought a very small hand-held spray/mister bottle at the local garden shop and used Triclopyr herbicide, sold under various brand names. We did not dilute the Triclopyr.
So far at least, it appears to work. The larger the tree, the longer it takes for it to die. One-inch trees will be bare of leaves in 4-6 weeks, 3-4 inch trees seem to take 8 weeks or so, and larger trees even longer.
And the work is fast – with a machete in one hand and the squirt bottle in the left, you can kill one of these nasty buggers in well under a minute. Just this summer, Trish and I killed acres of this “Tree from Hell” and just have some clean-up work to do in the 2009 growing season.