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Master Gardeners of Goodhue County

Master Gardeners of Goodhue County

Borrow a Weed Wrench and Be a Buckthorn Buster

Terry L. Yockey, Goodhue County Master Gardener

Why should you find and remove all buckthorn from your yard and gardens?

Let's start with why buckthorn is so destructive. Buckthorn produces berries with zillions of seeds that are eaten and then dispersed by the birds. The seeds germinate easily and then become zillions of baby buckthorns that soon grow into thickets of buckthorn that choke out all the existing native shrubs and other vegetation including the chokeberries, serviceberries and high-bush cranberries (Viburnums) that feed the birds and other fauna.

Once the buckthorn has totally taken over an area it becomes the only food source for the birds living there. On the surface this might seem okay, but buckthorn berries are extremely diuretic and pass right through the birds without giving them the nutrition that they need to survive. Even worse, the more they must eat buckthorn berries because there is no native vegetation, more baby buckthorns are produced. It is a vicious cycle.

It isn't enough that buckthorn grows so thickly that it crowds out the native shrub understory, to add insult to injury the roots and leaves are even allopathic. That means that like black walnuts most plants cannot survive growing nearby. So not only does it shade and crowd out all the native shrubs it also poisons any flora trying to grow underneath. Without the woodland plants to hold it, the soil erodes washing native plant seeds into nearby streams and ravines and making any future re-growth impossible.

If you still aren't convinced that buckthorn is a scourge, I will add one more reason to hate it for those of you that farm. Buckthorn is a host for the crown rust fungus (Puccinia coronata), which harms oats and it is also a host for Asian soybean aphids that damage soybeans and spread many other horticultural viruses.

Buckthorn is fairly easy to identify especially later in the fall when it keeps its green foliage long after most shrubs and trees have lost their leaves. The leaves are glossy, small and pointed and the fruits are in clusters of ΒΌ inch black berries. The bark resembles that of native cherries or plums, but if you scrape off a small section of the outer bark you will find that buckthorns have a distinctive bright orange heartwood underneath. You can find good photos of the leaves and bark on the MN DNR website at www.dnr.state.mn.us.

I won't lie to you--eradicating buckthorn isn't easy. If you don't correctly remove the plant you can end up with ten times as many buckthorns that come up from the roots and trunk. If you have mature buckthorn on your property that have a large trunk the best way to kill the tree is to cut it down to six inches or less from the ground and then immediately brush or spray an herbicide containing glyphosate onto the stump. Don't wait even a few minutes to paint the stump (especially in spring) because once the sap starts to ooze it will form a barrier rendering the herbicide less effective.

Choose a product that contains at least 25% glyphosate and preferably an even greater percentage. The ingredients label will give you the exact percentage if you read it carefully. There are other chemicals that will also kill buckthorn, but I don't recommend them because they can be very toxic and glyphosate becomes neutral when it hits the soil. I have had personal experience as to what a more toxic product can do when a friend used another herbicide for buckthorn growing in my garden and to this day nothing grows in the area where it was sprayed.

For smaller buckthorn there is a handy tool called the Weed Wrench that clamps onto the stem and easily levers the plant right out of the ground roots and all. The Goodhue County Master Gardeners have purchased a Weed Wrench that you can borrow free with a minimal security deposit that will be refunded when the Weed Wrench is returned. You can sign up to borrow the Weed Wrench or get a free fact sheet on buckthorn at the U of MN Extension office located at the Government Center, Room 201, 509 West 5th St, Red Wing, MN. Please call Robin at 651-385-3100 for more information on availability. View our video on buckthorn.