Ailanthus: Tree of Heaven, or tree from hell?

The yard behind us has several Ailanthus altissimas. Most of you know this tree. It's found in most American cities, anywhere there is a little soil and no one to check its growth. It grows between bricks on abandoned buildings,  in cracked concrete in alley ways, and has invaded native forests in at least 30 states. The tree is native to China, Taiwan, and Northern Korea. Because of it's rapid growth, it was imported to the United States by William Hamilton, a Philadelphia botanist whose estate, The Woodlands, is a few blocks from us. It was used as a street tree until people realized how short-lived the tree is, and how malodorous it is. Then it lost favor. But it was already too late. The tree spread quickly.

It's bloom seems to occur at the same time as Privet (Ligustrum sinense Lour.) which abounds in our neighborhood as hedges. The smell for the first day or so is actually pleasantly sweet. Despite my loathing of this particular tree, I noticed with delight bees clambering about the flowers when I was watering the top roof deck last  Thursday. Then the rain came. Old, wet ailanthus pollen smells like only one thing, despite what others say, it smells like cat piss.

The rain from the tropical storm Andrea helped wash the pollen from the tree and down to the ground. A thick coating is everywhere, including the leaves of our Hosta garden which is below this tree. I try to wash the pollen of the leaves as best as I can as soon as possible after a rainfall. I have not always been able to manage this though, and have found later after the pollen dries out, that it adheres to the leaves like Velcro. Then, if allowed to remain til the next rain, the re-sodden pollen will weigh the leaves down enough that they break.



If all this pollen slogging wasn't enough, after the pollen falls, the flower scapes dry, and eventually also fall. The part which had connected the scape to the tree, being heavier than the rest, falls first. This end also can be quite pointed and sharp, so when it hits a big broad Hosta leaf it shoots right into it. You get enough holes in one leaf, and you can forget about it helping the plant thrive. The leaves look like they've been used for target practice by the squirrels.

Some sources including the Plant Conservation Alliance, Alien Plant Working Group, www.nps.gov claim that ailanthus produce chemicals which prevent the establishment of of the plant species nearby. This might explain why I have such trouble getting new Hostas to thrive, unless I plant them in pots on top of the soil surrounding the tree.

Seedlings hide beneath the leaves of the Hostas, and if left to grow more than a year, are difficult to pull and get all of the roots. It's worth spending an hour or so to eliminate as many of the little time bombs as I can possibly find.

Last spring, as the pollen began to fall, I covered the Hostas with some old sheer curtains. I'd shake the pollen off every day or so. I left them on until most of the flower scapes had fallen as well. I then noticed that none of my Hostas bloomed last summer. I don't know for certain, that it was because of covering them, but it made me want to try something different this year. I'm hoping I can suspend some protection above them to keep the things from shredding the leaves. I'll let you know how it works.

I would be remiss to not mention the connection between ailanthus and the tree's most famous relation, the metaphoric "A Tree Grows In Brooklyn." I vaguely remember reading the book decades ago, long before I had an ailanthus in my life. I wonder if I'd read the book differently today?