How to Kill Grass in Flower Beds & Keep it Out

While a lawn full of thriving grass is ideal for any proud gardener, this growth is less welcome when it spreads to take over nearby garden beds. Aggressive turfgrass species and grassy weeds can invade the bare soil in your flower bed; not only does this ruin the aesthetics of the bed, but the grass can also steal precious water and nutrients from your other plants. 

Methods to kill grass in flower beds naturally include hand-pulling, smothering the grass, or solarizing the grass. For severe infestations, chemical means of control involve the use of a selective or non-selective herbicide to kill the grass. To keep grass out of flower beds, you can install landscaping fabric, landscape edging, add a layer of mulch, or grow groundcover plants. Preemergent herbicides are also a good choice if you have a recurring issue with grass growth in a garden bed. 

How Does Grass Spread to Flower Beds?

Grasses are able to spread using either overground stolons, underground rhizomes, or a combination of both. Also, each grass plant can scatter hundreds of seeds that may end up in your garden beds. This growth habit means that any bare soil in your flower bed is vulnerable to invasive grass species. Many of these grasses are incredibly challenging to get rid of, particularly if they’re allowed to mature and establish themselves in the soil. 

a flower bed with blue flowers next to a lawn

Types of Grassy Weeds in Flower Beds

Some common examples of grassy weeds include crabgrass, goosegrass, Bermuda grass, creeping bentgrass, and nutsedge.

Crabgrass

Crabgrass is an annual grassy weed that will appear on your lawn or garden beds between the spring and late summer. It has flat, wide, pointed blades, and stems that are short and purplish green in color. Crabgrass also grows clusters of small flowers. This weed is particularly difficult to get rid of as it has the ability to regrow roots from its stem nodes; it’s necessary to remove every part of the plant, including all roots and rhizomes, to completely eradicate this weed.

Goosegrass

Goosegrass is an annual grassy weed that grows most vigorously in the summer months. It looks very similar to crabgrass, having wide, flat blades; you can distinguish this weed from crabgrass by the flattened white center on its leaves. Like crabgrass, you’ll need to remove all parts of the goosegrass to eradicate it completely. 

Bermuda Grass

Bermuda grass is a type of warm-season grass that has an aggressive growth habit. Even if you don’t have it growing on your lawn, Bermuda grass can invade your flower beds as a grassy weed. This grass type is particularly hardy and fast-spreading, making it another challenging weed to get rid of. You’ll need to kill Bermuda grass to prevent it from choking out your other plants or grass.

Creeping Bentgrass

Creeping bentgrass is a cool-season grass type that will grow aggressively in cool temperatures and wet soil. Although this is another type of turfgrass, creeping bentgrass is considered a weed when it invades lawns and garden beds unintentionally. This grassy weed has blue-gray tapered blades that can grow up to 4 inches tall. 

Nutsedge

Nutsedge is a perennial sedge grass that grows most vigorously in the spring and summer, but can persist all year-round. This grassy weed has a distinctive ‘V’ shape that differs from normal grass, which is typically rounded. The two different types of nutsedge are yellow nutsedge and purple nutsedge; they are distinguished by the color of the flowers that this weed grows. As nutsedge spreads by underground rhizomes, it can form weed colonies that persist for years in lawns and flower beds. 

How to Kill Grass in Flower Beds

There are several methods you can use, both organic and chemical, to kill grass in flower beds. Methods to kill grass in flower beds naturally include hand-pulling, smothering the grass, or solarizing the grass. As a last resort, you can kill grass in flower beds using a chemical weed killer.

Hand-Pull Grass

For minimal infestations of grass in flower beds, the easiest and most straightforward way to remove it is to hand-pull. For this method to be effective, it’s crucial to remove all parts of the grass plant, including roots and rhizomes; most types of grasses are able to regrow from any parts that remain in the soil. 

Method:

1. Moisten the soil by watering it lightly the day before you plan to hand-pull the grass. This will ease the process, particularly if you have clay-heavy or overly dry soil. Avoid adding too much water or attempting to carry out this method after a heavy rain; if the soil is too wet, it’s more likely that parts of the roots will break off during removal.

2. Put on some gloves and begin pulling the grass plants out of the soil. Grasp the grass plant as close to the ground as possible before pulling it up, slowly but firmly. Again, this technique is to avoid breaking off root fragments. If the grass is stubborn, try twisting it as you pull upwards. Make sure you remove the entirety of the grass’ root systems along with the upward growth.

3. After removing all of the grass plants, place them in a warm, sunny spot to allow them to dry out. You can then place the dry grass onto your compost heap. If you don’t have a compost heap, dispose of the grass using a suitable alternative method. 

4. Keep monitoring the bed for regrowth and remove as necessary. It’s likely that you’ll have to repeat the previous steps several times before you completely eradicate the weeds.

Smother Grass

An excellent organic method to kill grass in a flower bed is to smother it. This method kills weeds by depriving them of sunlight, interrupting their process of photosynthesis and causing them to die off. Although this method takes a couple of months to work, it will effectively kill all grass and weeds in the bed. 

Method:

1. To increase the effectiveness of this method, you should first reduce the grass as much as possible. You can do so by mowing or cutting the grass to the soil line, or by tilling the soil with a hoe or spade.

2. Gather sheets of cardboard, newspaper, or a similar alternative material. Place the sheets on top of the affected bed. If using newspaper, layer about 5 to 10 sheets to create a thick barrier. Make sure not to cover any wanted plants, as this method will kill those off too.

3. Press the sheets down as close to the soil surface as possible. The easiest way to do this is to place wooden boards on top of the sheets before standing on them. 

4. Using a hose or watering can, soak the sheets with water. This will help to anchor them in place.

5. To further improve the effectiveness of this method, add a layer of mulch atop the sheets. This will add more weight to the covering and will block all sunlight from reaching the weeds.

6. After about 2 months, all weeds and grass beneath the cover should be fully dead. If you have used a biodegradable material like newspaper or cardboard, you can leave it in place; it will decompose over time and act as a slow-release fertilizer for the soil. If you’d rather remove the covering, you can do so at this point providing all weeds are completely dead. 

Solarize Grass

Solarization is a method to kill grass in flower beds by harnessing the power of the sun. This method involves placing clear plastic sheeting across the soil surface; the plastic sheeting amplifies the sun’s rays, causing the underlying soil to rise in temperature significantly. The heat that the sheeting generates will cause the grass and any other weeds to die off. For this method to be effective, you must carry it out during the late spring to summer. 

Method:

1. Till the soil in the garden bed using a spade or tiller to expose the grass’ roots to the air and sun. This step will also bring weed seeds to the surface, making them vulnerable to the effects of the sun too.

2. Cover the garden bed with clear plastic sheeting, overlapping the sheets where necessary. Avoid covering any plants you don’t wish to kill. After laying the sheeting, use heavy objects like rocks or timber to weigh the edges down.

3. Leave the sheets in place to allow them to do their job of killing the grass plants; this method takes an average of about 4 weeks to work. If you live in a particularly hot and dry region, you may only need to leave the sheets in place for 2 to 3 weeks.

4. Once all of the grass in the bed is dead, remove the sheets. 

5. Before planting anything new in the solarized bed, add a topdressing of compost to the soil. This will replenish the nutrients and microorganisms that were lost during the solarization process.

Use Chemical Weed Killer

If you have a particularly severe or widespread infestation, you may need to use a post-emergent chemical grass killer. As the chemicals in these killers can be so harmful, it’s best to use such treatments as a last resort. You have the choice of using either a non-selective herbicide, such as those containing glyphosate, or a selective herbicide, designed to kill the grassy weeds only. Take note that a non-selective herbicide will kill all plants it makes contact with, not just the weeds.

Method:

1. Purchase either a selective or non-selective herbicide. Read the label of the product to ensure it’s safe to use around the plants in your flower bed. You should also take note of the application and safety instructions and follow them carefully.

2. Apply the herbicide directly to the blades of the unwanted grass. For liquid formulas, it’s best to use a wand-style sprayer; this will enable you to accurately target the grass with little to no overspray on your wanted plants. If the grass is very close to your wanted plants, you can protect them with cardboard or an overturned bucket. If using a granular formula, add about ½ inch of water to the bed after application. 

3. Monitor the grass over the days following the application. It shouldn’t take long for the growth to turn brown and die off; if any parts remain green, reapply the herbicide as necessary. Avoid digging up the weeds too soon to allow the herbicide to soak down into the roots. 

4. After several days of the grassy weeds appearing brown and dead, dig them up from the bed.

How to Keep Grass Out of Flower Beds

After removing the grass, you can take some extra measures to prevent it from returning. To keep grass out of your flower beds, water properly, mulch the soil, install landscaping fabric or edging, and treat the bed with a preemergent herbicide.

Water Adequately

To avoid encouraging the growth of grassy weeds, make sure to only add as much water as your garden bed needs. Excess watering will invite weeds and grass into the bed, in addition to encouraging their deep root growth. To keep grass out of flower beds, water adequately, in addition to keeping an eye out for low spots in the soil. If you notice any pooling, you may need to level the soil to prevent areas of standing water.

Add a Layer of Mulch

A layer of mulch will keep grass out of flower beds, as well as bringing a host of other benefits to your soil. Mulch helps the soil to retain moisture, regulates the soil temperature, and can be used to improve the aesthetics of a planting bed. It works to suppress weed growth by providing shade to the soil surface; this blocks sunlight from reaching weeds and weed seeds, preventing them from germinating and growing. 

Materials you can use as mulch include:

  • Bark
  • Cardboard
  • Compost 
  • Glass chips
  • Grass clippings
  • Leaves
  • Straw
  • Woodchips

Grow Groundcover Plants

There are a few different plants you can grow as groundcover plants, also known as ‘living mulches’. These plants serve as a living alternative to mulch or landscaping fabric; they provide a covering for the soil, choking out the growth of grassy and broadleaf weeds. 

The types of plants you can grow as groundcover plants include:

  • Brass buttons
  • Bunchberry 
  • Clover
  • Creeping phlox
  • Epimedium
  • Golden moneywort
  • Lamb’s ear
  • Lamium
  • Lily-of-the-valley
  • Thyme
  • Wild ginger

Install Landscaping Fabric

A low-cost method to keep grass out of flower beds is to install landscaping fabric. The fabric blocks sunlight from reaching the soil surface, preventing the germination and establishment of unwanted grass and weeds. You’ll still be able to water the bed as normal with landscaping fabric installed; the fabric is permeable, meaning water will still be able to pass through and reach the soil.

Method:

You simply lay the fabric over your garden bed, cutting holes for new or existing plants. This will act as a barrier to significantly reduce the growth of weeds and grass in the underlying soil. 

Install Landscape Edging

You can install metal or stone edging to keep grass out of flower beds. The edging works to prevent the spread of grass and weeds to your flower beds by serving as a blockade between the bed and the surrounding soil.

Metal Landscape Edging:

Metal landscape edging is available to purchase as narrow metal strips with attached stakes. You install this type of edging by driving the stakes into the ground.

Stone Landscape Edging:

To install natural stone landscape edging, you’ll first need to dig a trench around the bed about 2 inches deep. You then lay the stone inside the trench to create the barrier. You can build up the walls of the edging by stacking several rows of stone on top of each other; this is known as dry-stacking.

Treat Beds with Preemergent Herbicide

A chemical means to keep grass out of flower beds is to treat the bed with a preemergent herbicide. These herbicides are specifically formulated to prevent the germination of seeds, killing grass and weeds before they get a chance to establish themselves. Take note that due to this formulation, preemergent herbicides will have no effect on grass or weeds that are already growing. You also need to make sure that the product you choose is safe to use around the existing plants in the bed.

Method:

1. Before treating the bed, hand-pull all weeds currently growing in the soil.

2. Purchase an appropriate preemergent herbicide for the grass or weed you want to prevent. Read the label of your product carefully to ensure it’s safe for use around your existing plants. Also, take note of the application and safety instructions for your particular product. 

3. Distribute the preemergent herbicide evenly across the soil surface in the bed. If you used a granular product, add about ½ inch of water immediately after treating the soil. 

4. After about 60 to 90 days, you may need to add another treatment to the bed to combat any new seeds that have made their way into the soil. 

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