Two common invasive plants you’re seeing right now

As you drive Indiana roads or walk your property this time of year, you’ve likely noticed unwanted plants quickly filling ditches, fence lines, and forest edges.

Many landowners want to protect their landscapes but aren’t always sure what they’re seeing or what action to take. Two invasive plants of increasing concern are garlic mustard and poison hemlock—both non‑woody invasives that spread aggressively but can be managed with timely action.

Garlic mustard is a highly invasive biennial that spreads rapidly by producing hundreds of seeds and by altering soil chemistry in ways that harm beneficial fungi and native plants. It grows early in spring, giving it a competitive advantage in forest understories, and can form dense colonies within just a few years. Garlic mustard produces foliage the first year, then flowers and sets seed in its second year before dying. It is identified by triangular, toothed leaves. The good news is that garlic mustard is relatively easy to control: pull plants before seed formation and dispose of them in sealed trash bags, or repeatedly cut second‑year plants to prevent seed production.

Poison hemlock presents a different challenge—and a serious safety concern. This fast‑spreading biennial can grow up to 10 feet tall in its second year and produces small white flowers in umbrella‑shaped clusters during June and July. Its fern‑like leaves cause it to be mistaken for other plants, but poison hemlock can be reliably identified by the purple blotches on its smooth stem. Correct identification matters because poison hemlock is highly toxic and can be fatal to humans and livestock. Control includes mowing before plants set seed, carefully hand‑pulling small infestations with proper protective equipment, or using labeled herbicides while plants are actively growing and before flowering.

If you are ready to take steps to protect your property and Indiana’s natural areas, Purdue Extension is here to help. For detailed guidance on identification and control, consult Poison Hemlock (FNR‑437‑W) or contact the Putnam County Purdue Extension Office.

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