A habitat-improvement rite of spring: slashing and burning bountiful buckthorn
A co-worker shared an intriguing piece with me today, about my least favorite invasive plant species, European buckthorn. The exotic shrub infests a little 10-yard-thick riparian area adjacent to a pond behind my home, so twice a year, I tear it out. Removing the buckthorn really opens the area up nicely, and I see lots of warblers and other songbirds using that riparian strip all year.
According to a piece in the Science and Technology section of the May 25 edition of The Economist, that’s no accident. Seth Magle, of Lincoln Park Zoo in Chicago, believed he’d find evidence of more predators where buckthorn exists, so – according to the magazine – he set up motion activated cameras in 35 wooded areas around the city.
Anyone who walks trails in the Upper Midwest, including the Twin Cities, sees the impenetrable understory of buckthorn across the region. The stuff grows so thick that it shades out everything underneath. Even other pesky exotics like garlic mustard can’t survive and relegate themselves to surviving along the woodland edges. Next time you’re walking a trail, look into a stand of buckthorn. You’ll see nothing underneath it, just bare ground. No native ferns, spring emphermals, herbs, or anything where a bird or any other creature can hide a nest.
Magle’s hypothesis is that lack of cover makes happy hunting ground for predators, and his research bears that out. Per The Economist, he saw more coyotes and raccoons searching areas in the spring where buckthorn is common.
My conclusion? Keep killing buckthorn. My most effective method has been pulling it out roots and all. I don’t like using chemicals to treat stumps because I’ve found the roots intermingle with good shrubs and even trees, and chemical treatments can kill those plants, too. Tearing it out by the roots is hard manual labor, but I have a small area to worry about – and three increasingly strapping sons to help me. In labor-intensive larger areas, like my dad’s 90-plus acres in southeast Minnesota or larger metro parks, buzzing off the buckthorn shrubs (or trees), then treating the stumps is the only way to go. Buckthorn, by the way, doesn't go away after cutting, pulling, or poisoning it once, because birds keep spreading its seeds.
Per a recent Star Tribune story, some efforts are trying to take buckthorn control to the next level and get some biofuel mileage out of it. Great idea. Anything that results in dead buckthorn has my blessing.
The Economist points out another nasty little quirk about buckthorn. Its leaves contain a toxin call emodin that discourages browsing by deer and other critters. Other researchers tested emodin on embroyonic frogs, and it killed them. What happens when those leaves fall off and emodin leaches into streams? The researchers indeed discovered the natural toxin in some ponds. Wonder if it’s in the one behind my home.
We’ve been hearing a lot about declining frog populations around North America. Could invasive buckthorn be playing a role?