Tree of heaven? Invasive pest vector more like tree of Satan
Q
I heard that we shouldn't plant a tree of heaven because it's invasive and host to some invasive pest species. Could you explain?
A
The tree of heaven (Ailanthus altissima) is native to China but has become an invasive tree in the United States. It can be found all over California (and other parts of the country) and can grow just about anywhere. It's been found in cities and agricultural areas, on riverbanks and even along railroad tracks. It can grow
3-6 feet per year and can produce extremely large quantities of seeds within two to three years. Its roots produce a compound that kills any other plants nearby (a trait called allopathy), so it easily takes over by killing its competition. It also tends to produce many root suckers (which are also allopathic).
The tree of heaven has very large (3 feet long) compound leaves with smooth-edged leaflets, giving it an exotic appearance. The bark is green on young trees but becomes gray and smooth, with a webbed appearance in maturity. Female trees produce many winged, papery seed pods (called samaras) that can be red, yellow or green and, if you didn't know any better, are quite attractive. The tree has an unpleasant odor that has been likened to cat urine and rancid peanut butter.
This odious tree is also host to two destructive pest insects: the spotted lantern fly and the marmorated stink bug.
Marmorated stink bugs, besides being stinky, are obnoxious in that they will destroy many economically important food crops in California. They attack grapevines, pears, apples, stone fruit, berries, figs, almonds, hazelnuts and citrus. In colder weather they have also been known to invade houses in large numbers. These shieldshaped bugs are about
5/8 inch long with mottled brown wings that have banding along the outer edges. When disturbed, they will release a foul odor. Of course, something this obnoxious would hang out in the tree of heaven.
The spotted lantern fly, another invasive pest, has been causing problems on the East Coast but has not arrived in California. It lays its eggs on nonplant materials such as firewood, outdoor furniture, shipping crates or vehicles. In this way, you can see how easy it would be for it to make its way to California. It affects at least 40 crops including grapes, stone fruit, apples, berries, walnuts, almonds and hops. It is 1 inch long and about half an inch wide. At rest, its wings form a tent-like shape over the body. True to its name, the wings are gray with black spots and the bottom third of the wing has a darker, bricklike pattern. The tree of heaven is the spotted lantern fly's preferred host.
We hope that by discouraging people from planting this tree (and working to eliminate the already existing one), we can slow or stop the spread of the spotted lantern fly to California. It may sound mean to advocate for the destruction of these trees, but think of the hops (and the other crops that could be lost).