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GLOSSY GREEN LEAVES IN LATE FALL SPELL TROUBLE
Everyone loves to look at colorful fall leaves. In a few weeks, we'll marvel at the reds, yellows, oranges and scarlets.
This fall, train your eyes to search for green leaves on small trees after all the red, yellow, orange and scarlet leaves have cascaded from the tree branches. The green leaves you see still clinging to branches in late October and early November after all the colorful leaves have fallen are buckthorn.
A few weeks ago, I spent a half day removing and digging out the roots from a very handsome nine-year-old fernleaf buckthorn (Rhamnus asplenifolia) that was planted right outside my office window in 1993 by a landscape contractor. It had grown to about 15 feet and, as the name implies, sported very attractive fern-like leaves. It also produced -- for the first time this summer -- small black berries.
I liked the tree a lot until I discovered the berries. When eaten by birds, these berries are spread across my yard and the surrounding neighborhood and the seeds sprout into seedlings that will not become atractive fernleaf buckthorns. Rather, the seedlings revert to the non-native, invasive parent buckthorn species.
Removing my attractive ornamental buckthorn was a lot of work but the tree had to go. I can't very well go on writing with a clear conscience about buckthorn eradication when I have a source of the problem growing in my yard. My tree was okay as long as it didn't produce berries but, given the plant's propensity to propagate from seed, it was time to reach for the saw and shovel.
Later in the same week, I made a house call at a home on Lake Waconia where a beautiful landscape had been established 20 years earlier. Some of the trees and shrubs at this site, unfortunately, have become overgrown and unsightly. I was invited to the site to offer advice on pruning and general tree and shrub maintenance.
A dozen of the woody plants in this landscape are buckthorns -- a popular landscape plant two decades ago. Native to Europe, buckthorn was imported to North America in the late 1700s and widely planted as hedging material until 1930. Ornamental varieties of buckthorn (like my fernleaf variety) continued to be sold and planted right up until the last few years. The buckthorns on this Waconia lot were full of beautiful 1/4-inch diameter berries. And, you guessed it, tiny buckthorn seedlings are popping up everywhere.
I've written about buckthorn before, and perhaps you wish I'd find a new topic, but buckthorn is a serious problem in Minnesota yards and wooded areas and each of us can play a part in preventing a total takeover by this invasive plant.
You may have heard the term allelopathy. It refers to suppressive effect of one plant on another through production and release of natural compounds. Black walnuts possess allelopathy. Tomatoes and peppers and some other plants will not grow in soil where black walnut roots are present. Sunflower seeds also cause this phenomenon. There are no plants growing under my bird feeders.
Buckthorn puts all the pieces together for total takeover: A vigorous root system, mycorrhizal root fungi, a long growing season, hungry birds that spread the seeds, no natural predators and an allelopathic effect on other plants.
The first step in controlling the spread of buckthorn is identification. That's why I hope you'll stop and take a close look at the glossy, green-leafed plant this fall after the other leaves have fallen.
Mary Lerman, horticulturist with the Minneapolis Park and Recreation Board, says the woodlands and wetlands in Minneapolis are infested with common buckthorn. "One only needs to drive along Minnehaha Parkway, the River Road parkways, through Theodore Wirth Park and along Diamond Lake to see its devastation," she says. Some experts have written that, if buckthorn isn't removed soon, future generations will not have the opportunity to enjoy the flora and fauna of woodlands and wetlands.
Buckthorn eradication is complicated and labor intensive. If you have buckthorn present on your property, I encourage you to begin the process of eliminating it. The Minnesota Department of Agriculture and the University of Minnesota Extension Service have published helpful guidelines for fighting this invasive plant. Eradication procedures and close-up photos of the leaves and berries can be viewed on dozens of internet sites.
In some areas, homeowners and other volunteers have joined forces to eradicate buckthorn from entire neighborhoods. Perhaps you are just the person to begin a buckthorn removal campaign in your neighborhood.
Okay, I've said my piece...and I promise not to write about buckthorn anymore in 2002. By the way, my buckthorn removal project had a happy ending. I drove to a local garden center and bought a small but very attractive blue-needle Japanese white pine and planted it where the fernleaf buckthorn grew for nine years. I should have planted the pine in the first place.
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