A Green Pest

Wisconsin is home to 1,800 species of native plants. The summer is alive with the swaying prairie and in the winter, hardy evergreens hold their needles close. From the whispering driftless hilltops to the sandy beaches of Picnic Point, Wisconsin is second to none in terms of diverse greenery.

However, an invader lives in the quiet understory of our forests.

Buckthorn, an introduced and invasive species, is an ongoing problem in Wisconsin woodlands. Not-so-fun-fact: about four in ten of all federally threatened or endangered species are at risk because of invasive species!

Native to Europe, buckthorn was originally brought to America in the 1840s to be used as a decorative plant or a hedge. Since then, it has rapidly spread from Washington to Maine, having a particularly huge impact on Wisconsin with the help of our unsuspecting feathered friends.

Birds eat buckthorn’s numerous seeds and spread them quickly to new, faraway areas. There, they grow and form dense thickets that shade out native plant species. What could have started as a small hedge in your backyard could turn into a green monstrosity smothering peaceful native plants in our parks!

Those patches may look friendly, but they have bark and a bite. The thorn in the name comes from the pointed tip of buckthorn’s branches. Ouch!

Not all branches have this feature, however. Buckthorn is known for its incredible plasticity in growth form. Jargon aside, this means that buckthorn can grow as a tiny shrub lying across the ground, or a small-sized tree shading out plants beneath. It can be covered in spines like the name suggests, or it can have none at all. Each individual plant is its own individual, and this trait is what also allows it to conquer so many different terrains. Buckthorn can thrive in complete sunlight or under the canopy of tall oaks. It can overwhelm river-soaked clay beds or drier loams.

Buckthorn is certainly a mighty foe, but the battle isn’t hopeless. It may be impossible to completely eliminate these innocent-looking bushes, but daily efforts can help to reduce its impact. The Wisconsin DNR, Arboretum, and Parks Department all play vital roles in keeping our plant communities diverse and healthy.

Agencies and organizations like the WDNR and Parks Department tend to use a number of methods to reduce or eliminate buckthorn. Prescribed burning, mowing, and applying herbicide are common management techniques that combat buckthorn, but may be impossible for the average Joe. I don’t know about you, but I don’t own a flamethrower, or a flamethrower permit for that matter.

So, how can we help? The first step is knowing your enemy.

If you’re new to plant identification, you might be plant blind, that is, all plants look the same except for the ones with pretty flowers. Unfortunately, buckthorn doesn’t have pretty flowers but it does have a number of noticeable traits that can separate it from the green jumble beneath the forest canopy. Wood County’s department of land conservation has a great guide linked here↗ (opens in a new tab). The most obvious things to be aware of are the clusters of small black berries along the branches and its occasional sharp points at the ends of branches.

If you’re still not sure, though, the UW-Madison arboretum’s volunteer work parties are a great place to start. These work parties offer Madisonians a chance to help preserve the arboretum’s pristine natural areas, while also learning about the management and labor that goes into them. They are offered from February to December. Local experts and arboretum staff will help you get involved with hands-on experience. In the late fall months, help is needed to collect native seed and chop down unwanted plants, buckthorn included. You can find more details about these volunteer work parties here↗ (opens in a new tab).

If you find buckthorn on your property, the best thing to do is dig it up, but if that’s not possible then cut it down and apply herbicide containing glyphosate (like Roundup) to the cut stump so it can’t regrow from its expansive root system. The native plant-life will thank you.