Brushpiles: Tree of Heaven - Not a Good Neighbor

Posted: August 15, 2014

Brushpiles is the opinion page of Forest Leaves. It’s a place for you to write in and share your reactions and thoughts about recent articles in the newsletter. This Tree of Heaven piece was written by Laura Jackson in response to Bill Paxton's recent Tree of Heaven article.

I learned a lot from Bill Paxton's article on "Tree of Heaven" in the July 8, 2014 issue of Forest Leaves. That wasn't surprising, as Bill's articles are always very informative and interesting. Reading about Bill's research on Ailanthus altissima, or Tree of Heaven, brought back memories of my early childhood and my observations about this tree, so I thought I'd continue the topic and share some of my experiences and research about this remarkable species.

I grew up on a farm in southern Bedford County, just a few miles south of Everett, PA. As a young child, I was always interested in nature. Both of my parents allowed me to bring all sorts of creepy crawlies onto the back porch, which became my natural history museum. A good bit of the farm was forested and adjacent to state game lands, so I had hundreds of forested acres to explore. My father took time from his busy farming schedule to teach me the names of trees and their role in the forest. I had favorite trees to climb, where I would sit for hours – entertained by wildlife and the beauty of the forest.

When I was around ten-years old we drove to the Pittsburgh suburbs to visit family friends who had moved there from Everett. I remember playing with the other children and marveling at this strange tree – this very huge tree (or so it seemed to me) that grew in their backyard. I had never seen this tree in my woods. My friends explained that it was called Tree of Heaven before crushing some leaves so I could smell the "burnt peanut butter" odor, which I thought was kind of stinky. From then on, I always associated Tree of Heaven with Pittsburgh and I'd look for it on the steep hillsides in the city when we visited. I noticed it grew in odd places, where other trees didn't grow. I thought of it as strictly a city tree.

Fast-forward to about twenty years later when my husband and I moved back to my family farm after being away for twelve years. The farm hadn't really changed very much, but the little town of Everett certainly had. The Borough received an "improvement grant," so almost all the street trees in the downtown section were removed. Now the wide sidewalks contained big concrete planters holding stunted ornamental pear trees. Only one tree was spared in the downtown section along Main Street and that was a gingko, reportedly planted in honor of three brothers who went off to fight in the Civil War. There were plenty of trees on the side streets and in the outlying areas around Everett – including some Tree of Heaven – a tree that I never saw in Everett until about 15 years ago.

Although the downtown is still barren of trees, there is now Ailanthus almost everywhere else. If there is a small patch of dirt along the edge of a parking lot, there will be three or four Ailanthus competing for space. The dike that protects Everett from the Raystown Branch of the Juniata River when it floods is covered with Ailanthus. The Borough tried to eradicate Ailanthus on the dike after receiving a grant to control it, but to no avail. Side lots are turning into Ailanthus jungles. Just outside Everett is a steep hillside that used to be covered with redbud, but now the Ailanthus towers over the redbud. A few years ago, I asked the local PennDOT manager to spray the Ailanthus with herbicide, as the hillside is in their right of way, but PennDOT doesn't use herbicide in the late summer, I was told. Late summer is the time of year when Ailanthus should be sprayed, so the plant takes the toxin down to its roots. Perhaps PennDOT may be more willing when one of the trees crashes on the road during a storm. Everett is literally being taken over by Ailanthus.

Since we live just a few miles south of town, I've watched the steady march of Ailanthus as it gets closer to our property. Ailanthus is smothering an historic limestone kiln just south of Everett, in Black Valley where we live. Although I've shared information with the landowner on how to control Ailanthus, his attempted control methods were unsuccessful. Now some small clumps of Ailanthus are growing right along the road about a mile north of our property. Last year we even discovered a few small Ailanthus growing in our woods on Tussey Mountain, so we followed proper herbicide treatment to kill them. DCNR has a publication that details methods to eradicate Ailanthus. (1)

Mr. Paxton's concerns, that our efforts to eradicate Tree of Heaven are "mindless, expensive, and misdirected," are based on his research that shows the Tree of Heaven is, indeed, a noteworthy tree. I agree that it is truly a super tree and many of its qualities are to be admired. But, like anything else in the wrong location, Tree of Heaven creates problems when it grows in my forest – or any place in Pennsylvania's forests.

Mr. Paxton found that the Tree of Heaven "has no insect pests or diseases." While a landscape architect might feel that being pest-free is a valuable trait, it sends up a red flag to me. I want trees in my forest to be part of the food chain, to play an important ecological role in the web of life. Non-native trees like Tree of Heaven do not support insects, which feed many species of birds. Trees in my forest should support birds like insect-eating warblers and scarlet tanagers. Pennsylvania is a keystone state for scarlet tanagers in that about 20% of the world's population of scarlet tanagers breed in Pennsylvania. As a forest landowner, I feel responsible for helping to maintain the population of scarlet tanagers in Pennsylvania. If I had a forest of Ailanthus, I would be destroying the food source for these beautiful and important birds, as well as many other bird species. For more information on the importance of native plants, I recommend Doug Tallamy's excellent book, "Bringing Nature Home."  (2)

Some of us had the wonderful opportunity to hear Dr. Tallamy speak in 2013 at the Private Forest Landowner's Conference. I'm looking forward to the next conference in 2015. (3)

Ailanthus has remarkable properties in its ability to enrich forest soil, as Mr. Paxton points out. It is amazing that the tree contains so many nutrients in its dead leaves and branches; however, I've seen how Ailanthus forms thick clumps, which probably prevent other tree species from benefitting from those nutrients. If the high nutrient value only benefits Ailanthus, and not our native trees, then allowing Ailanthus to grow does a disservice to native forest species that could participate in the food web.

Just because Ailanthus possesses remarkable qualities does not make it a good neighbor. I think its qualities make it a bio-bully since it uses its arsenal of superlatives to displace our native trees – it produces toxins that prohibit other species from growing near it, it is perhaps the fastest growing tree in Pennsylvania so it outcompetes native trees, and traditional harvesting techniques merely stimulate it to grow more suckers. My highest priority is the ecological role of a tree and that property is more important to me than its potential as a timber or fuelwood tree. Others agree. Ailanthus is listed as a noxious weed in Vermont and is banned in Connecticut, Massachusetts, and New Hampshire, according to the USDA Plants Profile for Ailanthus. (4)

Research by Matthew Kasson, who received his doctorate in plant pathology and environmental microbiology from Penn State and studied clearcuts on state forests lands in south-central Pennsylvania, is quoted as saying, "It's the number one cause of native regeneration failure in clearcuts in Pennsylvania."  Kasson acknowledged there are other invasive species in Pennsylvania, but he said that Ailanthus does more damage than any other invasive tree in the research area. (5)

Most of us forest landowners value our forests for their wildlife and we find enjoyment in going to the woods where we find peace and solitude. In return, we have an obligation to care for our forests, to do all we can to protect and promote native species. Don't let Ailanthus take over your forest!