April 21, 2012 in Washington Voices

Dig or use herbicide to control garden grasses

Pat Munts
 

The garden is coming alive! Green sprouts are popping up all over the place. Drat, a lot of them are shoots of grass in the middle of the perennial and shrub beds. How do you get rid of it without destroying the whole bed?

There are two kinds of grass that commonly invade gardens. Annual grasses like bulbous bluegrass usually come up very early. It is short and fine-textured with roots that look like a bulb. These grasses will send up seed heads by early May and be done by June.

Running grasses like orchard grass spread by underground roots that can overtake a garden bed quickly. Orchard grass has thick, white, jointed roots that grow a few inches under the soil and will run several feet. It usually moves in from grassy areas around a bed or as a hitchhiker in a root ball.

Obviously, the best way to control grasses is to not let them get into a bed in the first place. For running grasses, English perennial gardeners used to dig a narrow, three-inch trench around beds that most grasses can’t cross. If you are moving plants from a bed that has grass, poke through the root ball for any long, white grass roots and pull them out.

That said, most of us aren’t that organized.

Small patches of grass can be dug out. This means you will need to be going after annual grasses very early in the spring before they start going to seed. For running grasses, loosen the ground around the patch and then gently pull the long root back to the mother clump and dig it out.

For beds that are totally infested, you are going to either have to deprive the grass of light or kill it off with herbicides. In areas where there aren’t many plants, cover the area with weed-block fabric, cardboard or 10 or 15 layers of wet newspaper. Don’t use black plastic; water can’t get through to the plants you want to keep. Cover that with a thick layer of fine bark, shredded pine needles or compost and leave it. Light can’t get through, so the grass dies.

Herbicides need to be used carefully because spray drift can damage or kill plants close by. There are herbicides specifically for use on grasses that won’t damage most plants, but check the label before you spray. Glyphosate (Roundup) can also be used, but it will kill anything it gets on.

Apply herbicides on a day when the temperature is going to be in the high 50s and 60s with no wind. Don’t apply if temperatures are above 80 degrees. Read and follow the directions. Use a small spray bottle to squirt it right where you want it. Cover desirable plants with buckets, boxes or garden pots before you spray. Leave them on for the day. If grass is growing too close to plants to spray safely, put some spray mix in a container and carefully paint it on the grass blades with a paintbrush. Follow up in a few weeks to catch the ones you missed.

Pat Munts has gardened in the Spokane Valley for more than 35 years. She can be reached at pat@ inlandnwgardening.com.


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