How To Kill The Grass In Your Flower Beds

Have you noticed that grass refuses to thrive in your lawn, but it's lush and green in your flower beds? Unless you’re ready to give up the blooms and create another area to mow, the grass has got to go. Grass spreads rapidly in flower beds as it steals nutrients and water. Even after getting rid of the visible blades, grass can leave behind seeds or an expansive root system and come back with a vengeance.

Killing or getting rid of grass in flower beds is an ongoing process. You’ll be more successful if you prevent the invasion with a physical barrier and tackle the problem as soon as you first see grass appear. Try these methods to prevent and kill grass in flower beds without damaging your other plants.

Organic Methods to Kill Grass in Flower Beds

These methods can be used to kill grass if it has not woven itself too far into the flowers you want to keep.

Vinegar: To be effective, use cleaning vinegar which is much stronger than apple cider or distilled white vinegar. Spray undiluted vinegar directly on the grass taking care not to spray other plants. Vinegar is most effective on young grass shoots and tender broadleaf weeds and you will see “death” within 24 hours. However, while vinegar will burn back the grass it will not kill the roots. Repeat the treatment as grass reappears and after rain showers or irrigation periods because they dilute the efficacy of the vinegar. 

Boiling Water: Heat the tea kettle and using care to avoid other plants, pour boiling water on the invading grass. It will kill the root system of the grass. 

Solar Power: If you want to turn a section of lawn into a flower bed, solarization works well to kill grass. Cover the area with a layer of clear plastic sheeting. The heat from sunlight will kill the grass and the roots. The grass and roots can then be raked out after tilling the soil and before planting flowers.

Chemical Methods to Kill Grass in Flower Beds

Garden center shelves are filled with products that will kill grass. Most are available in spray bottles with a premixed solution. Others must be diluted and applied with a home garden sprayer. Always read directions and take precautions when using these herbicides. They are non-selective which means they will kill not only the grass but also your petunias, lilies, and coneflowers. One method to prevent overspray is to use a piece of heavy cardboard to protect desirable plants.

Glyphosate, sold as RoundUp, KleenUp, Accord, Imitator, Eraser, Pronto, or Rodeo, is the most widely used herbicide to kill grass. A non-selective, post-emergent, broad-spectrum systemic herbicide, it is absorbed by foliage and kills the root system within 7 to 10 days. It is an effective grass killer but care must be taken to prevent overspray onto flowers. The U.S. Environmental Protection Agency does not consider glyphosate to be a human carcinogen.

There are other non-selective herbicides, Diquat (Reward™), pelargonic acid (Scythe™), glufosinate (Finale™, and others) that can be used to kill grass. These products do not translocate from the foliage to the root system and require repeated applications.

Physical Methods to Prevent Grass from Creeping into Flower Beds

Adding edging or a physical barrier between a flower bed and the lawn can help discourage grass from leaping into the bed as it grows. Before you choose an edging barrier, use a sharp, square-edged garden spade to cut straight into the ground along the flower bed line. Then make a 45-degree cut from the bed towards the first cut to form a trench that severs the root system of the nearby grass. Here are two edging choices:

Steel Edging: Available in strips or rolls in a variety of finishes, steel edging creates a rigid, uniform boundary to block grass. More expensive than plastic edging, it is more durable especially if you use a string trimmer to keep lawn edges sharp. Depending on the thickness of the steel chosen, the edging can last from 20 to 25 years.

Plastic Edging: Less expensive, lighter weight, and easier to install around curved beds, plastic edging will also block grassroots. However, plastic becomes brittle after extended sun exposure and may need to be replaced within five years.

Manual Removal of Grass from Flower Beds

My uncle, RD Hodges, a North Carolina State Extension Agent, loved to tell homeowners to use the Santa Claus method to remove grass from flower beds—Hoe, Hoe, Hoe. The pun was always followed by a groan, but it remains one of the most effective ways to make sure you get rid of grass and its roots. If removing grass by hand, use a garden trowel or hoe to loosen the soil so you can pull out the grass and its roots. If any small roots are left in the soil, the grass will reappear.