Tree from hell

Ailanthus samaras                                             Nicholas A. Tonelli/Flickr

There is a tree you may be noticing now, a ubiquitous tree with big frondy leaves composed of many leaflets, that appears to be in "bloom" with clusters of yellow-green or reddish-brown "flowers."

The tree is Ailanthus altissima, and those aren't flowers you're seeing on the female form. They are clusters of seeds packed in thin, oblong pods called samaras. As soon as the seeds ripen in the next few weeks, their aerodynamic samaras will carry them hither and yon, unleashing another generation of this pest tree to infest gardens, parks, woodlands and farm fields.

The common name may be "tree of heaven," but those of us who know it well call it the tree from hell or, alternately, “that hideous weed.”

Fast-growing, greedy, persistent and impervious to insects, drought, poor soil and pollution, the ailanthus is a prime example of an invasive exotic -- an imported plant -- capable of displacing more desirable native species. This invader quickly forms impenetrable thickets, and produces toxins that discourage other plants from developing nearby.

Also known as the "tenement palm," the ailanthus starred in "A Tree Grows in Brooklyn," the novel by Betty Smith that was made into a 1945 film classic about triumph over adversity. You have to concede that the ailanthus will grow virtually anywhere -- from cracks in the sidewalk, along highway verges and train tracks, at the edges of cultivated fields, on flat roofs and even in leaf-clogged gutters.

Its tenacity is astounding. It will re-grow from a cut stump, growing a sapling 10 feet tall the same season. It will send root suckers reaching into the surrounding earth, creating a host of baby saplings. And it sprouts readily from those seeds we mentioned, as many as 350,000 per tree.

Before you notice these devils in a shrub border or weedy flower bed, they've already grown three feet tall and established a tap root half way to China, their original home. As with so many pestiferous plants, ailanthus was deliberately brought into the country, in 1784 to a garden near Philadelphia, to be exact. It arrived a bit later in Western states, where it was planted by Chinese immigrants who used various preparations made from the tree in folk medicines.

Ailanthus thicket                                          NatureServe/Flickr

It's hard to imagine how it could be considered medicinal, since contact with the leaves and sap can cause contact dermatitis in the sensitive. The whole tree, and especially the male flowers, has a foul odor (described as similar to burnt peanut butter), leading to another pet name -- stink weed. Ailanthus means "reaching to heaven," and altissima means "tall," but some of us translate the Latin as "stinking to high heaven."

I do battle with these weak, brittle and entirely unwanted interlopers on a regular basis. Some years back, it was an ailanthus on my boundary that was struck by lightning, falling on my neighbors' vehicles and squashing their roofs like eggs. I've been digging up and cutting down ailanthus for years, with no visible reduction in their numbers.

Just the other day I was trying to remove a two-foot sapling from a bed I was clearing. After I had dug a 20-inch hole with no end of the root in sight, I took a hatchet to it; sadly, I have no confidence that the sucker won't live to sprout again.

I have had ailanthus seedlings peeking out between my outside steps, growing beside my foundation, poking out from under the porch and springing up next to the tomatoes. One renegade got started in the middle of a venerable old red cedar that stands at the top of my garden. Before you knew it, it was a 10-foot-wide parasol shading my poor little roses below.

Killing these trees isn't easy. You can't exactly spray the foliage of a 60-foot tree without harming all plants below, and it does no good to merely chop them down at the base because of the prolific re-sprouting that goes on. The trunk and foliage is just the tip of the iceberg; you have to get to the roots to do any good.

One method I’ve seen used with good success is to cut the trunks to manageable size -- two to five feet off the ground -- and then treat the stump, painting it with an herbicide like Ortho Brush-B-Gone concentrate with Triclopyr. After treating, cover the top of the stump with aluminum foil so rain won't dilute the weed-killer.

If the trees are really large, you can drill several holes in the stump and pour herbicide in them before covering. Another chemical that works is dicamba, sold as Vanquish and Banvel. Tip: You have to get the weed killer on promptly, within five to 10 minutes of whacking the tree down, or plant cells will seal the cut, preventing penetration. As always, use caution with these chemicals and follow directions to the letter.

Very few things in nature inspire such dire impulses in me as the ailanthus does. But when alien plants mount a hostile takeover, you have to fight back.