Crabgrass is one of the most prevalent weeds in Indiana lawns however it is also fairly simple to control. There are two main ways to prevent or control an infestation; cultural and chemical.

Crabgrass has an important growth characteristic which allows most controls to work. It is a warm season summer annual while most turf varieties planted in Indiana are cool season perennials. This means our desirable turf plants green up earlier in the spring so if we have a healthy, dense turf early in the spring, crabgrass never gets started. However it also means that when cool season grasses go dormant in the heat of the summer, crabgrass can thrive.

Cultural control is achieved by making sure your turf is well cared for and healthy. A healthy lawn will out-compete crabgrass and prevent it from becoming established. Using proper mowing techniques and following a good lawn fertilization program will help keep crabgrass from getting started.

Unfortunately, sometimes crabgrass will be a problem even if the turf is well-managed. Most lawns will have “better” and “worse” areas. There can be many reasons an area does poorly but often we find crabgrass in these locations. In these cases, sometimes we need to use chemical controls.

Chemical control is usually achieved by using pre-emergent herbicides. As crabgrass is an annual, it must establish itself each spring. As a warm season grass, it germinates after cool season species have already started to green up. Pre-emergent herbicides help prevent this initial germination and restrict seedling development by preventing root growth. Crabgrass seed begins to germinate when soil temperatures reach 57 to 64 degrees so application timing is critical. In most years you should apply by April 10 in Central Indiana. The online Growing Degree Date Tracker, located at: http://www.gddtracker.net/, can be helpful. Select “Crabgrass PRE” from the toolbar.

For newly seeded turf, including areas which have received spot seeding, you must wait until the grass has become fully established before applying most crabgrass products. Read the label for specific directions but most products recommend waiting until you have mowed the area several times. Using a product too early will result in it having the same effect on your desirable turf as on crabgrass – preventing it from becoming established by restricting root growth.

Products with the active ingredient siduron are safe to use on newly seeded Kentucky bluegrass, tall and fine fescues, perennial ryegrass and some cultivars of creeping colonial bentgrass (consult the label for specific cultivars). These require multiple applications 3 to 5 weeks apart and are fairly expensive. However they may be an option if crabgrass looks like it may be a big problem. For any pesticide, be sure to read and follow all label directions.

Post-emergent control is more difficult, however a few products are available. Read and follow label directions for the specific product as, if used improperly, they can damage desirable species. Also, these are generally only effective on very small crabgrass plants.

Consider how much crabgrass is acceptable. You can virtually eliminate it but this takes intense management and significant expense. Most people can tolerate a few crabgrass plants in their lawn.

Annual Yard and Garden Show

The 2019 Gardenfest, sponsored by Boone County Master Gardener Association and Purdue Extension — Boone County, will be held on Saturday, April 6 from 9 a.m. to 3 p.m. at the Boone County 4-H Fairgrounds Farm Bureau Community Building in Lebanon. Some of the many activities and events for the day include:

Featured Gardening Speakers:

10 a.m. “Growing Roses is Easy” by Mark Nolan, Indiana Rose Society

11:30 a.m. “Changing the World with Plants” by Kelly Frank, Horticulturalist

1 p.m. “Gardening for Shade” by Amy Mullen, Spotts Garden Center

The first 300 attendees will receive a free tree seedling. Master gardeners will be on hand to assist with your garden questions. Door prizes will also be awarded. Vendors featuring flowers, garden art, herbs, succulents, hostas, horticulture information, gifts, and more will be on hand.

You may also pick up free Purdue Extension garden publications and have your soil pH tested. Pre-owned garden tools and items will be available for sale and sandwiches and homemade desserts will be sold at the Garden Café. The Pansy Patch will have fun activities for kids.

Admission is free and anyone is invited. For additional information please contact the Extension Office at 765-482-0750 or e-mail cemanuel@purdue.edu.

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