My massive black walnut tree has behavior issues.
With the help of hordes of nut-addled squirrels, it drops a mess of debris and stains the concrete with hulls and shells. I hold my breath when people walk their dogs or kids through the alley, fearing someone will get beaned by a nut. My neighbor calls my tree a bully, which is an understatement considering it has been slowly murdering her white birch. Please do not plant a white birch anywhere near a black walnut tree.
I have grudging respect for this tree after 15 years of living with it and suffering innumerable plant fatalities. This is a tree that defends its turf and won’t cohabitate with just any plant. If you have a black walnut tree, I can tell you that besides the plants mentioned in the September/October issue of Northern Gardener, there are some beautiful shrubs that are tolerant of juglone, the compound produced by black walnut roots, leaves and nuts.
I’ve got a row of lilac and arborvitae growing under my black walnut despite the amount of shade thrown by the tree. They provide alley screening for me and must get just enough sun for themselves from the open alley space. Last year I planted a cluster of Arctic Fire dogwood within the black walnut’s dripline, and they’re doing just fine. In fact, the dogwood shrubs are menaced more by roving bands of rabbits than the walnut tree. (If one sometimes goes out the back door in one’s bathrobe to launch a garden clog at a rabbit, does that make one eccentric? Asking for a friend.)
There’s a mature burning bush, or euonymus, under the black walnut’s drip line–though it’s old and gnarly enough that I think it’s more of a “tree form” burning bush than, well, a bush. I’ve had some success with weigela, so I’ve got a couple of the Tango variety, with their lovely burgundy foliage, and a new cluster of My Monet weigela. These are stunning dwarf shrubs with variegated foliage and pink flowers, and they’re among my favorite new additions.
Serviceberry is a good companion tree or large shrub for a yard with a black walnut, and I’ve just added a cultivar called Standing Ovation for a spot under power lines. It has a columnar shape and grows to about 15 feet. I’m not concerned about it being on the outer edge of the walnut tree’s dripline, but I am worried it gets too much shade from a mature nearby crabapple. Wish me luck–I’m excited to have a beautiful serviceberry for its spring blooms, summer fruit, and fall color.
Bottom line: There are plenty of great shrub options if you have a black walnut on or near your property. Do research before buying and planting anything. Check several extension sources and look for a consensus opinion about juglone tolerance if sources conflict. Check out the University of Minnesota Extension Service’s publication, “The Best Plants for 30 Tough Sites,” www.conservancy.umn.edu. Other extension services that offer good black walnut info: Pennsylvania State University, www.extension.psu.edu, Iowa State University, www.hortnews.extension.iastate.edu, and the University of Wisconsin, www.hort.extension.wisc.edu.
Susan Barbieri is a St. Paul writer and longtime journalist who has worked for a variety of local and national publications, including the St. Paul Pioneer Press, Minneapolis Star Tribune and Minnesota Monthly.
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