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Imagine going to all the trouble of removing a section of your lawn to plant a garden bed, only to see grass reappearing. When grass creeps into planting beds, it becomes a weed that competes for the same nutrients, sunlight, and space that your flowers and edibles rely on to thrive. Grass can choke out the bed’s plants and create a messy appearance. While chemical herbicides might seem like the easy way to tackle undesirable grass in your flower beds, there are safer approaches. Keep reading to learn how to keep grass out of flower beds without reaching for chemicals.
Cover the area with cardboard or newspaper.
You can tackle remaining grass in an area before starting your flower bed with smothering. Also known as layering or composting, smothering involves covering existing patches of grass with several layers of overlapping cardboard or newspaper. This technique works by blocking any sunlight from reaching the grass, ultimately killing grass blades and weakening their root system. Wet the paper product before arranging it in the flower bed and anchor it down with mulch, soil, or rocks.
Keep in mind that it can take about 8 weeks for the grass to die, so this method requires some patience, and if you already have plants in the bed, you’ll need to work carefully around them. The other benefit of using cardboard or newspaper is that it boosts soil quality as it breaks down.
Install root barrier edging.
Installing a physical barrier between the flower beds and the surrounding lawn can help keep grass out. Grass spreads underground through rhizomes and stolons, explains Gaetano Virone, a landscaping and irrigation expert and founder and head of Environmental Designers Irrigation in Wall Township, New Jersey. Use garden edging made of a sturdy material like wood, steel, brick, or stone to help block grass roots from spreading into the beds. “Install a physical root barrier edging at least 6 inches deep around the entire bed perimeter,” recommends Virone.
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Lay landscape fabric in the bed.
Lay commercial-grade landscape fabric underneath your soil or amendments, says Virone. This woven material effectively blocks sunlight to keep out grass. “I’ve seen homeowners skip this or go too budget-friendly, and then wonder why they’re pulling grass shoots two seasons later.” To use it, first prepare the ground by removing any existing grass. Then lay the fabric over the flower bed and keep it in place with staples or small garden stakes. “Overlap the seams by at least a foot,” says Virone. Be sure to cut a hole large enough for plants that will go in the garden bed.
Dig a sloping trench.
Trenching is another safe alternative to herbicides. It involves digging a trench between the edge of the garden bed and the lawn, which forms a moat so grass can’t grow across the area. The best way to do this is by using a sharp shovel to dig 4 to 6 inches deep in a V-shape along the edge of the garden bed. For best results, leave the grass side of the trench vertical, but slope the flower bed side about 45 degrees. Keep the trenched edge clear by occasionally mowing or trimming.
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Add a layer of mulch.
Mulching is another way to suppress grass growth in garden beds. It serves as a barrier to prevent sunlight from reaching grass seeds. Pine bark, shredded hardwood, straw, and shredded leaves are recommended materials to use for mulching. The best way to stop grass in the bed is to temporarily layer the new area with at least 8 inches of mulch (for about 4 weeks). After planting, add a 2- to 3-inch layer of mulch in your flower beds to help prevent grass from reappearing.
Set up irrigation zones.
Virone suggests setting up irrigation zones for your landscape. “If your existing lawn zones are throwing water into the new bed area, you’re actively encouraging grass to reclaim that ground,” he warns. “Redirecting or capping those heads to match only the new planting zone’s needs is something we address on almost every residential redesign we do, and it makes a real difference in what takes root and what doesn’t.”
