Keep Invasive Purple Loosestrife Plants Out of Your Garden

The eternal question for gardeners often seems to be, “is that a flower, or is that a weed?” It can be difficult to know what plants in your garden are supposed to be there, and what’s not — and sometimes, even the prettiest plants can wreak havoc on your yard and the ecosystem. That’s the case with invasive purple loosestrife. While it looks lovely, it’s not native, and it’s proven difficult to contain even in the most carefully maintained gardens. Here’s what you need to know about this troublesome plant, and how to get rid of it.

What Is Purple Loosestrife?

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Purple loosestrife (Lythrum salicaria), native to Europe and Asia, typically grows in wetland climates. It made its way to the United States on cargo ships in the mid-1800s. It’s posed trouble in gardens and wetlands ever since, as it outcompetes native plants, provides no food or shelter for native species, and negatively impacts the landscape in natural areas.

What Does Purple Loosestrife Look Like?

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To recognize whether you’re dealing with this problem, start by looking for a plant with purple flowers. Those flowers typically have five or six petals, and they grow in ‘spikes’ of up to a foot in height. A good trademark to look for is a square-shaped stem.

Worth noting, though, is that a few native species resemble this invasive plant. Before taking action to rid your yard of the plant, make sure you do, indeed, have purple loosestrife and not a lookalike.

Learn surprising facts about invasive plants.

How to Get Rid of Purple Loosestrife

“About five years ago, I replaced overgrown lawn with a mixture of natives and herbs for birds and butterflies. But now, purple loosestrife has appeared along my property line. Is there any way to get rid of it, or am I doomed to a loosestrife takeover?” asks Birds & Blooms reader Marge Berger of Athens, Wisconsin.

Horticultural expert Melinda Myers says, “Thanks for doing your part to keep invasive plants out of the ecosystem. Removing these invaders as soon as you find them, before they set seed, is the best way to control small populations.

Plants in your neighborhood may be providing the seeds that are infesting your plantings. Work with neighbors to rid your area of this pest. Some severely infested communities have enlisted the help of galerucella beetles, which eat the leaves and prevent the plant from flowering.

For information, contact the Wisconsin Department of Natural Resources. Officials work with schools and citizen groups to raise, release and monitor the beetles. Those battling purple loosestrife in other states can contact their local municipality, university extension office, or Department of Natural Resources.”

Next, learn how to manage garlic mustard: a noxious invasive weed.

Sources

• Minnesota DNR, “Purple loosestrife (Lythrum salicaria)“
• Michigan Invasive Species, “Invasive Species: Purple Loosestrife“