Glossy Buckthorn: How can a shrub be so harmful?

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Glossy Buckthorn: How can a shrub be so harmful?

It’s National Invasive Species Awareness Week, so here is a profile of one of the top invasive plants in Maine. Do you recognize glossy buckthorn?

Glossy buckthorn (Frangula alnus) is a tall, understory shrub from Europe that was brought to North America in the early 1800s as an ornamental shrub, primarily to serve as hedges. But this woody plant escaped from yards and landscaped areas long ago, invading forests, fields, wetlands and lake shores.

Glossy buckthorn is extremely hardy and able to thrive in a variety of soil and light conditions. It also out-competes native plant species with its fast growth rate and extended growing season — glossy buckthorn leafs out earlier in the spring and holds its leaves later into fall, allowing it to continue to grow when most native species are dormant.

The leaves and bark of glossy buckthorn are not a gourmet treat for local wildlife. Look closely at a glossy buckthorn leaf and you'll rarely see any spots or small holes. It has no specific insect predators in North America. Deer also avoid it, instead munching on native species and furthering glossy buckthorn’s competitive edge.

Combine these characteristics with this shrub's plentiful seed production and it's not hard to see how it can very quickly dominate a forest or streamside area, pushing out beneficial plants.

Why glossy buckthorn matters

Impact on wildlife and forests

To us humans, a lakeshore dominated by glossy buckthorn just looks like a lush sea of bright green leaves. But invasions of glossy buckthorn reduce the abundance and diversity of butterflies and bees, which are valuable pollinators. In addition, glossy buckthorn out-competes native plants, resulting in fewer potential host plants for leaf-eating insects like caterpillars, which are the main food source for many nesting songbirds. Forest trees are also at risk from glossy buckthorn competition. Because it is somewhat shade-tolerant and can grow densely in the forest understory, glossy buckthorn can dominate and crowd out the seedlings and saplings of desirable forest trees like white pine. Foresters around New England are finding that they need to take action in order to ensure that desirable trees are able to come in after planned harvests, rather than thickets of glossy buckthorn.

Bad for our lakes and streams

Because glossy buckthorn shades out and out-competes native groundcover plants, it's bad for water quality. Native groundcovers help stabilize soil and retain and absorb rainwater. Without these native groundcover plants, rain water can move faster and pick up more pollutants including soil particles that empty into nearby bodies of water. The soil is rich in phosphorus which can feed nasty algae blooms.

What you can do

First, learn to recognize this invasive species!  Plants can grow in a shrub form with many stems coming from the base, or as a small tree up to 25’ tall. It can look like a young birch or cherry, with white lenticels on the bark, but the leaves have smooth edges (no teeth).  Glossy buckthorn’s branching pattern is alternate along the twig – one leaf per node.  Flowers are small, 5-parted, white-yellow, and and appear where the leaf meets the stem in early summer. Glossy buckthorn can have unripe green fruit, somewhat ripe red fruit, and ripe black fruit all on the same plant at once. Roots are a deep red color.

Second, look for this plant on your property, and take action to remove it. Do you have glossy buckthorn lurking at the edge of the stream, in your woodlot, or even planted as a hedge? Consider what you might do to get rid of it, or replace plantings over time. For more information on control methods, visit the Maine Natural Areas Program's invasive plant photo gallery. You’ll find many more photos to help you identify glossy buckthorn and links to videos demonstrating control techniques.  

Glossy BuckthornGlossy Buckthorn