It’s late fall in Minnesota. Peak color in the woods is over and most of the native trees and shrubs have dropped their leaves in preparation for winter. Now, take a moment to look out at the nearest woodlot. If you see shrubs that still have green leaves, they are likely the nasty and invasive buckthorn.
Buckthorn is a shrub/small tree that can reach a height of up to 25 feet. It often has multiple stems and dark green, glossy leaves. The bark is grey to brown with yellow inner bark and orange heartwood. In the fall older, seed-bearing plants will have numerous quarter-inch black berries. Buckthorn is very hardy and reproduces through stump sprouts and by seed that is spread via birds and animals. It grows in sun or shade and on a variety of soils. There are a variety of species that can look a lot like buckthorn including dogwood, chokecherry, pincherry and crabapple so be sure you have properly identified the plant in question.
Buckthorn was brought in from Europe in the mid 1800s as a hedging material. The plant soon escaped and invaded forests, yards, parks and roadsides. The plant is very aggressive and shades out native shrubs and small trees that grow in the mid-layer of the forests. Along lakes and rivers, buckthorn shades out native, deep-rooted species causing concern for erosion and degraded water quality. In woodlots, buckthorn out-competes native shrubs and forbs that provide important browse for many species of wildlife. It can also restrict the natural regeneration of tree species.
Controlling buckthorn can be very difficult and time consuming. Plants that are two inches in diameter or larger are best controlled by cutting the stem at the ground and then treating the stump with a herbicide like Garlon to prevent re-sprouting. Stumps should be treated immediately (within two hours) after cutting. The best time to cut and chemically treat buckthorn is late summer through the fall. Small plants are best controlled by pulling the entire plant out of the ground. Plants that are pulled with all the roots intact will not re-sprout. Burning can also be effective but you must be very careful to adequately heat the base of the shrub to interrupt the vascular system that transports water and nutrients. Buckthorn control is a long-term commitment. Seeds can remain viable on the forest floor for up to five years. Patience and persistence are necessary for winning the battle against buckthorn once it is established. We recommend getting aggressive at the first sight of buckthorn in your woodlot.
The Minnesota Department of Agriculture has declared buckthorn a restricted noxious weed. This means that the sale, transportation or movement of this plant is prohibited statewide by the Minnesota Department of Agriculture.
For more information on buckthorn identification and recommendations on control, contact your local Soil and Water Conservation District or Natural Resources Conservation Service.