Plastic lawn edging is a common choice for homeowners who want a quick, low-cost way to define garden beds and keep grass from creeping into planting areas. Rhonda Ferree, a horticulture educator with University of Illinois Extension, explains that plastic is inexpensive and easy to install, but it also has poor durability and an artificial appearance. Understanding its limits before you dig can save you from the frustration of edging that refuses to stay put. For other options, compare metal edging and stone edging, and see how to install lawn edging.
What to Expect from Plastic Lawn Edging
According to the University of Illinois Extension, plastic is the most common edging material used by homeowners because it is inexpensive and easy to handle. However, Ferree points out that of all the materials used as edging, plastic is probably the hardest to install for a lasting, stable result. Many people have experienced the frustration of plastic edging that simply will not stay in the ground.
Plastic edging comes in different profiles. Experts generally agree that round-top edgings are better because they do not sink as easily as flat types. If you choose flat plastic edging, the Illinois Extension recommends nailing a 1 x 1 inch strip of treated wood along the bottom of each strip where possible, using galvanized nails. This helps stabilize the plastic and reduces movement over time.
Frost heaving is another common problem. The Illinois Extension notes that most frost heaving can be stopped by using grooved or lip-style edging, steel anchoring stakes, and proper installation procedures. These features help lock the edging into the soil and resist the upward push of freezing ground.
Planning Your Plastic Edging Installation
Before you break ground, you need to contact 811. The national before-you-dig service states that anyone who plans to dig should contact 811 or visit their state 811 center’s website a few business days before starting any digging project. This includes installing lawn edging. The service will arrange for the approximate location of buried utilities to be marked with paint or flags so you can avoid hitting underground lines. The 811 site warns that even shovels can harm utilities.
Once utilities are marked, decide on the shape of your edge. The Royal Horticultural Society (RHS) advises that broad, sweeping curves are easier to maintain than intricate curves or complex shapes. Straight edges create a formal look and give clear definition between lawn and border. Curved edges create a natural feel and are good for breaking up long, rectangular gardens.
To mark a straight edge, the RHS suggests tying a string between two canes or pegs so the string is taut and at ground level. For curved edges, use something flexible like a garden hose, rope, or string. View the marked-out edge from various angles, including from an upstairs window if possible, to get a good view of the whole shape. Make adjustments until you are happy with the positioning.
Cutting the Trench and Installing Plastic Edging
With the line marked, you can begin cutting the trench. The RHS recommends using a half-moon edging tool or a flat-backed spade. If you use a spade, mark a depth of 7.5cm (3in) on the blade with tape and insert it to that depth. Start at one end of the line and insert the blade into the ground, standing on the flattened top of the blade to ensure it is inserted fully. Work your way along the line, taking small steps so that the cuts just slightly overlap to create a continuous cut.
After cutting, go back along the line and pull up narrow strips of grass by hand. To lift larger pieces, slide the blade of a spade underneath. Walk down the line and look at it from both ends to check that the cut is neat and even. If necessary, cut out further pieces with your edging tool. The RHS notes that the unwanted grass can be composted or stacked in a separate pile to rot down into soil.
Now you can place the plastic edging into the trench. If you are using flat plastic edging, follow the Illinois Extension’s advice and nail a treated wood strip along the bottom for extra stability. For lip-style or grooved edging, insert steel anchoring stakes according to the manufacturer’s instructions. The RHS says that installing wood or metal edging helps retain the shape and makes edge trimming easier, and the same principle applies to plastic: a well-secured edge will hold its line better.
Keeping Plastic Edging in Place
Plastic edging tends to shift because it is lightweight and flexible. The Illinois Extension explains that flat types can sink over time, which is why round-top profiles are preferred. The wood strip trick adds weight and a wider base, making it harder for the edging to tilt or push up. Illinois Extension adds that grooved or lip-style edging with steel anchoring stakes and proper installation stops most frost heaving.
When backfilling the trench, press the soil firmly against both sides of the edging. The RHS emphasizes that a well-defined lawn edge with a decent drop down to the border will help keep mulching material in place. Aim for a drop of about 7.5cm (3in) from the lawn surface to the border soil. This not only holds mulch but also discourages grass runners from crossing into the bed.
Maintaining a Clean Edge with Plastic Edging
Even with plastic edging installed, regular maintenance is necessary to keep the line crisp. The RHS advises redefining edges with a half-moon edging tool at any time of year. Work your way around the lawn, inserting the blade downwards to cut away slivers of grass that have grown over the edge. This redefinition can be done annually and makes trimming the edge easier throughout the season.
For routine trimming, the RHS recommends using edging shears after each time you mow your lawn. When grass is in full growth, this may be as often as once a week. Hold the shears upright so the blades are beside the lawn edge. Keep the handle attached to the lower blade steady, and move the handle attached to the upper blade to cut overhanging grass. Take small sideways steps and slightly overlap your cuts to create a neat, crisp edge. Afterwards, check for any missed tufts of grass and rake up the clippings. Short sections can be flicked into the border with a hoe to rot down.
If your plastic edging has shifted or heaved, you may need to reset it. Remove any soil that has accumulated, reposition the edging, and re-secure stakes or add new ones. The RHS notes that if your soil sits wet over winter, it is best to wait until it dries out before working on edges to avoid compacting the soil and damaging the lawn.
Frequently asked questions
How can I keep plastic edging from popping out of the ground?
The University of Illinois Extension suggests using lip-style or grooved edging with steel anchoring stakes to resist frost heave. For flat plastic types, nailing a treated wood strip along the bottom adds weight and stability. Proper installation, with the edging set at the correct depth and soil firmly packed around it, also helps.
Is plastic edging suitable for curved beds?
Yes, plastic edging is flexible enough to follow curves. The Royal Horticultural Society recommends broad, sweeping curves because they are easier to maintain than tight, intricate shapes. When marking a curved edge, use a garden hose or rope to lay out a smooth line before cutting the trench.
How often should I trim the edges?
The Royal Horticultural Society advises trimming lawn edges with edging shears after each mow. During periods of active grass growth, this may be once a week. Regular trimming keeps the edge looking neat and prevents grass from growing over the plastic edging.
For more details on choosing and installing plastic lawn edging, visit our plastic lawn edging page. You can also explore other materials and styles in our lawn edging types section and read our full comparison of lawn edging materials.
