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Serving: IN

Recognize, control these invasive plants

Slideshow: Conservation groups step up efforts to root out invasive plants.

Who knew decades ago that popular landscaping species such as Bradford pear and burning bush would spread into woodlots and forested areas? Most people know now, and Emily Finch, invasive species specialist for the soil and water conservation districts in Daviess, Dubois and Martin counties in Indiana, is doing her best to make sure everyone else finds out soon.

These three districts are using a second Clean Water Indiana grant, which extends through 2023, to continue employing Finch to provide outreach and technical assistance to landowners. The CWI grant also includes surveys of poison hemlock and phragmites in the three-county area.

Farm Progress posed questions to Finch so she could better explain why it’s important to focus on invasive species. Refer to the pictures in the slideshow to identify some of the most common invasive species.

What can people do on their own to control invasive plants? Identify what invasive plants you have. Honeysuckle and multiflora rose leaf out before native trees, making them easy to spot. Some annuals like Japanese stiltgrass can only be identified in summer. Once you know what you have, choose which areas you want to start controlling first. That could be small, isolated patches, mature plants with lots of fruit or just the area of your property that is easiest for you to access. It’s important to prioritize where to start.

When is the best time to control invasive plants? It depends. Poison hemlock and Japanese Stiltgrass need to be controlled before flowering so they don’t produce seeds. Phragmites and Japanese knotweed are best controlled when sprayed after they reach full growth, and depending on herbicide selection, after flowering. Fortunately, most woody species can be controlled throughout the year.

Adjust your treatment method based on the season. If you’re applying a foliar herbicide to leaves, spring and fall can be ideal since many invasive plants will be green when nearby native vegetation is not, creating a more targeted herbicide application. Cut-stump applications can be done just about year-round, except during spring sap flow. The only time basal bark can’t be used is on hot summer days or when the bark is wet.

Choose a treatment that works best for you and the targeted invasive species. The best time to control an invasive species is when you have time!

Where can people get more information? Contact the Southern Indiana Cooperative Invasives Management group at They have several regional specialists around the state to help landowners. Your local SWCD may also have someone who can help. The USDA Natural Resources Conservation Service has cost-share programs available to help landowners pay for control efforts.

Is constant scouting and continued control necessary? Unfortunately, invasive species management is an ongoing need. But the first control efforts are the hardest. Once you have your invasive populations more or less under control, it’s about monitoring and maintenance. Many invasive species have seed banks that can last for 10 years or more. Keep an eye on areas that had invasive plants and control any new seedlings. By regularly monitoring areas like roadways, waterways and forest edges, you can quickly catch and remove new infestations.

What are the most common and damaging invasive plants a landowner might encounter? Some common woodland species are amur or bush honeysuckle, multiflora rose, Japanese vine honeysuckle and autumn olive. You’ll find them in the forest understory, but also in denser populations on forest edges where they get more sunlight. Wintercreeper vines are also becoming more common.

If you have open areas, you might see poison hemlock, johnsongrass or sericea lespedeza. In roadside ditches or on pond edges, the tall grass known as common reed or phragmites is also common.

The most damaging species are those left to grow unchecked. Certain sites are at more risk. For example, a mature forest may see little impact from Japanese honeysuckle vines. But after a timber harvest, if vines that were on sunny edges aren’t managed, young trees are quickly strangled.

A newer invasive, Japanese stiltgrass, is an annual grass that is very shade tolerant and can create thick dense patches on forest floors, shading out other plants, while wildlife like deer don’t eat it. It is also one of the more difficult plants to control. Treatment timing is very specific during the summer, and must be repeated every year for about 10 years to exhaust the seed bank.

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