This site is for people who like plants -- growers, enthusiasts, aesthetes, novices and professionals, those who appreciate wild things and those who appreciate the cultivated. I garden in Chelsea, and I've been visiting people's yards for 20+ years in the course of my work. My goal is to make this blog a community project, so if you share my interests, please consider becoming a participant and contributing content -- Guerin. Info:

Wednesday, July 20, 2011

Around town with corktrees

The corktree is a hardy and handsome shade-tree from Asia that has made it onto the short list of trees recommended by Michigan Extension and the City of Ann Arbor. The corktree is also on the list of noxious invasive pests published by the Bureau of Land Management. Read on and then go figure.
One of many on Brooks
The Amur corktree, Phellodendron amurense, likely made its first appearance in Ann Arbor at Nichols Arboretum in 1920. Additional plantings were made in subsequent years of that decade, and there may(!) remain several large specimens in the glade at the bottom of the hill. Around town you might run into the occasional mature specimen growing in yards in older residential areas. The City of Ann Arbor also started planting them in modest numbers along the sidewalks starting in the 70's.
a specimen at Felch/Miner
The overall form of the corktree is distinct -- assuming you are practiced in that kind of thing. The tree can can be told from a distance by its shelf-like branching, somewhat resembling a menorah. Typically with a short trunk, it often grows at least as wide as tall. The bark is light-grey and corky, although 'cork' as a product is not derived from this tree.

Another Brooks St specimen
You might confuse a corktree for the more familiar ash. Both groups have stout twigs on which pinnately-compound leaves are arranged in pairs.  The cork-tree leaf, however, will emit a turpentine aroma when crushed (the tree is in the citrus family); and the twigs never have a terminal bud.

The fruit, when fresh, looks like a small cherry. Older fruit can be retained for a year, in which case it is hard and dark. Both smell just like the fruit of our local Zanthoxylum (prickly-ash, which is also a citrus relative), and a lot like sumac fruit and the rind of a lime.

The tree's bad reputation comes from its tendency to appear as a volunteer in unwanted places. Matthaei Botanical Gardens director Bob Grese said, "I don't know if I would plant any more of these trees." He said the Arb workers have had to pull out thousands of seedlings. The plant is also shows up in city parks that are being restored as natural areas.

Whereas cork-tree hasn't yet made it onto the list of "Least Wanted" trees in Michigan, it has proven to be a locally noxious pest in the New York City Parks, several Audubon wildlife sanctuaries in eastern Massachusetts and around Philadelphia.

To visit some local corktrees,  check the out two largish specimens growing along the driveway entrance to Matthaei Botanical Gardens. In town a very interesting specimen graces the front lawn at 513 Onondaga; and on the west side you can admire a tall specimen at 1937 Ivywood. And let me know if any of these have been removed, if you would. Some city street-side plantings are found at the corner of Fifth St and Pauline (on Fifth), 1111 Miner, 1129 Bydding and along Brooks starting in the 1000 block.


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