Kill your lawn dead, dead, dead
Properly removing your existing grass lawn is one of the most important components of installing a WaterSmart landscape. If the existing grass lawn is not completely killed, including the roots that might be deep underground, it will come back and ruin your new landscape. Premature planting of your new garden will mean years of follow-up weed removal, which you do NOT want to do. So make sure the lawn is dead, dead, dead!
There are a few different methods to kill your lawn, including herbicide application and solarization. Before you kill your lawn, you must:
Determine what kind of grass you have
- Cool season turf: Marathon, Fescue, Bluegrass, or grasses that stay green in the winter
- Warm season turf: St. Augustine, Bermuda, Zoysia, or any rhizomatous grass (grows horizontally under or along the ground and often sends out roots and shoots) that is brown in the winter
Determine your method of removal
Cool Season Grasses. Here are a few options of how to kill cool season grasses:
- Smother with mulch, no plastic
- Strip and flip using a sod-cutting machine
Warm Season Grasses are harder to kill, especially in the winter when they are dormant, because you have to kill all the roots. Here are a few methods of removal:
- Solarization (cover with plastic)
When in doubt, assume you have at least some warm season grass, so you’ll have no regrets later.
Some methods for killing the grass lawn
- Natural turf removal: A natural way to remove turf and preserve the soil’s ecology is to strip the turf, and for the next two weeks, water the area to encourage grass to re-sprout, and remove all new growth.
Solarization: If you have six to eight weeks time, a preferred alternative is to use the process of solarization, which involves covering the area and using the sun to heat up the soil to levels that will kill the weed seeds without damaging the healthy soil microorganism.
- Cover your entire lawn with black plastic sheets and weigh down with bricks or rocks.
- The lawn must stay covered for at least 6 weeks to ensure that it has been properly killed.
- Water and fertilize the (hopefully) dead lawn for a couple of weeks after removing the plastic to make sure all the grass is dead.
Mow the dead grass to a very short length and remove with a sod cutter or shovel.
According to the UC Guide to Healthy Lawns, the most effective way to kill your grass lawn is through the application of a nonselective herbicide, like glyphosate. Glyophosate is the main ingredient in “Roundup”, which is readily available at most garden supply stores. Since Bermuda grass and some other grasses are dormant in the winter, they must be treated with herbicide when they are actively growing in the remainder of the year. While herbicides are undeniably effective, they also pose threats to the environment if used improperly. It is up to the consumer to determine the costs and benefits of herbicide use. Here are some key points to consider if you plan on using this technique:
- Water, grow, spray, kill; repeat. Apply herbicide while your turf is actively growing (non-winter months) to ensure proper absorption. Don’t apply if it is expected to rain within 24 hours; don’t water for 24 hours.
- Do not disturb the sprayed area for at least 7 days, as it may take up to 7 days for the plant to fully absorb the herbicide.
- Once the grass has died, mow the lawn at a very low setting—as close to the bare soil as possible—and collect the resulting material.
- Water and fertilize the (hopefully) dead lawn for a couple more of weeks; spraying any live shoots that appear. Remove remaining material with a sod cutter or shovel.
NOTE: In order to prevent unnecessary pollution and the destruction of non-targeted plant material, it is important that herbicide is not applied in windy conditions or 24 hours before a rain event. Visit Cornell University’s Pesticide Management Education Program for more information on glyphosate. Before applying any herbicide, be sure to read and understand the label. When it comes to herbicide, the label is the law.
Tree of Life Nursery provides an easy-to-read guide on how to kill your lawn.
The techniques listed above are not meant to be exhaustive. Learn how to kill your lawn in greater detail with UC Guide to Healthy Lawns or visit the UC Sonoma County Master Gardeners for more information.