How to Kill Grass in a Rock Garden

A properly designed and managed rock garden is visually pleasing and adds distinction to a property. A rock garden requires care and maintenance, though, including continuous removal of grass and weeds as seeds carried by wind and birds drop into the area and germinate. Stepping stones make the chore of weeding easier in a large rock garden. Once unwanted grass takes root, a number of methods will eliminate it.

If plastic sheeting to block weeds and grass was not installed during the construction of the rock garden, you can add it. Black plastic that is 4 millimeters thick kills grass by blocking its access to light, oxygen and water.

Place pieces of black plastic sheeting in problem areas, and cover it with gravel or other small stones that complement the garden design. Leave a 2- to 3-inch open space between the stems of the rock garden plants and the plastic.

Black plastic kills and blocks most grasses and weeds but not bermudagrass (Cynodon dactylon), which has sharp sprouts that pierce plastic. Landscape fabric is better-suited for bermudagrass. Bermudagrass is winter hardy in U.S. Department of Agriculture's plant zones 5 through 10, depending on the variety. It is considered a noxious or invasive plant in many U.S. locations.

Geotextiles, also called landscape fabrics, block sunlight and are difficult to puncture or tear. Landscape fabric benefits plants with roots under problem areas because it allows water and oxygen to penetrate.

Place pieces of geotextile over areas where the grass is sprouting in the rock garden, and cover it with gravel or another mulch material. Keep the fabric from touching garden plants.

Although plastic sheeting and geotextile kills existing grass and prevents new grass growth, over time, seedlings can sprout on dust or sediment that settles on top of the sheeting or fabric, even when either is covered with a gravel mulch.

Several household products kill grass and weeds. Place any one of these liquids in a spray bottle, and use it full strength on the grass: bleach, white vinegar or apple cider vinegar.

Spray it directly on the grass clump. Avoid doing this on a windy day to ensure the mist does not drift to other plants in the rock garden. If it rains or as new growth appears, reapply the product.

Borax and table salt are two more household products that kill grass. Sprinkle either borax or salt directly on the grass. Lightly mist the site with water to activate the granules.

A vodka, liquid dish soap and water cocktail kills weeds and grass.

Container

2 tablespoons vodka

3 drops liquid dish soap

2 cups water

Spray bottle

Mix 2 tablespoons of vodka with 3 drops of liquid dish soap and 2 cups of water.

Pour the mixture into a spray bottle.

Spray the mixture directly on the rock garden's grass until it runs off the grass blades. Apply it at noon on a sunny day. The sunlight in conjunction with the cocktail dehydrates and kills the grass.