What edging does and how to create it

Edging is a border that separates your mulch bed from the lawn or hardscape around it. It stops mulch from spilling into grass, keeps grass roots from creeping into the bed, and gives the whole landscape a finished look. You create an edge by cutting a clean line along the perimeter of the bed, usually 2 to 4 inches deep, then optionally installing a physical barrier—metal, plastic, or wood—to hold that line in place over time.

The simplest approach is a cut edge with no barrier: you dig a shallow trench along the bed's border and keep it maintained. A physical edging material makes the edge last longer between maintenance visits and gives a more formal appearance. Most home gardeners use one of three methods: a spade-cut edge (free, temporary), plastic or metal edging (inexpensive, lasts several years), or wood edging (more expensive, looks natural, needs replacement every 5 to 10 years).

Key Takeaways

  • A clean edge is a shallow trench cut 2 to 4 inches deep along the bed's border, made with a flat spade or edging tool.
  • Mark your edge line with chalk, spray paint, or a garden hose before you cut, so the line is straight and you do not have to guess.
  • Cut on a slight angle (about 45 degrees) rather than straight down, which makes the edge more stable and easier to maintain.
  • Physical edging materials like plastic or metal strips hold the line longer than a cut-only edge, but a cut edge alone works if you refresh it once or twice a year.
  • Edging works best when done in spring or fall when the soil is moist enough to cut cleanly but not waterlogged.

Mark your edge line before you cut

Start by deciding where your edge will run. Walk the perimeter of the bed and look for the natural boundary between mulch and lawn. If the bed is new or irregular, use a garden hose to lay out the line you want—curve it, straighten it, step back and look at it from the house. Once you are happy with the shape, mark the line so you can see it while you work.

Chalk, spray paint, or flour all work. Spray paint (the kind sold for marking utility lines) is fastest and most visible; chalk works on dry soil but washes away in rain; flour is temporary and biodegradable. Mark the line on the grass side of where you will cut, so your blade follows the mark and the mark disappears as you go. For a curved edge, mark every foot or so. For a straight edge, mark the start and end points and snap a chalk line between them.

Choose your cutting tool

A flat-bladed spade is the standard tool for edging and works well for most soil types. The flat blade cuts a clean line and the long handle gives you leverage. A half-moon edger (a semicircular blade on a long handle) is designed specifically for this job and is easier on your back if you have a lot of edging to do. A power edger (a wheeled machine with a vertical blade) is worth renting if your bed is very long or your soil is hard clay.

Avoid a shovel with a curved blade—it digs rather than cuts and leaves a ragged edge. Make sure your spade is sharp; a dull blade tears roots and soil instead of slicing cleanly. If your spade is dull, sharpen it with a file or whetstone before you start, or rent a sharp tool from a garden center.

Cut the edge at a 45-degree angle

Stand at one end of your marked line, facing along the edge. Hold the spade so the blade is tilted at about 45 degrees—not straight up and down, but leaning away from the bed. Push the blade straight down into the soil to a depth of 2 to 4 inches (deeper in loose soil, shallower in clay). Step on the top of the blade to drive it in if the soil is hard.

Once the blade is in, pull the handle toward you slightly to cut the soil, then step back and move to the next spot. Overlap each cut slightly so you do not leave gaps. Work along the entire line in one direction. The angled cut creates a small wall that holds the mulch in and is less likely to collapse than a vertical cut. It also makes the edge easier to maintain later—when you refresh it, you follow the same angle.

If you hit a root, cut around it rather than trying to chop through it. If the soil is very hard and your spade is not going in, water the area the night before and try again when the soil is slightly softer. Wet soil cuts more cleanly than dry soil, but waterlogged soil is hard to work in and clumps on your blade.

Install physical edging if you want the edge to last

Once your edge is cut, you can stop there—a cut edge alone looks clean and works fine if you are willing to refresh it once or twice a year. If you want the edge to hold its shape longer, install a physical barrier in the trench you just made.

Plastic edging is the most common choice. It comes in rolls, is inexpensive (usually $0.50 to $1.50 per linear foot), and lasts 5 to 10 years before becoming brittle. Lay it in the trench so the top edge sits just above ground level (about 1 inch above the soil), which stops mulch from spilling over. Stake it every 2 to 3 feet with landscape spikes or landscape staples. Metal edging (usually aluminum or steel) costs more but lasts 15 to 20 years and looks sleeker. Install it the same way as plastic.

Wood edging (cedar, composite, or pressure-treated boards) gives a natural look and costs $1 to $3 per linear foot for materials. Lay the board in the trench and find it with landscape spikes driven through the board into the soil. Wood rots over time—cedar lasts 5 to 10 years, pressure-treated lasts 10 to 15 years—so plan to replace it eventually.

Maintain your edge through the season

A cut edge without a barrier will blur over time as grass creeps back in and mulch settles. Refresh it every spring and again in midsummer if needed. Use the same spade and angle, following the existing edge line. This takes 15 to 30 minutes for a typical bed and keeps the edge sharp all season.

If you installed physical edging, check it in spring to make sure the stakes are tight and the barrier is sitting at the right height. Mulch settles over time, so you may need to add more mulch to bring it back to the top of the edging. If the edging has shifted or sunk, reset it. Plastic and metal edging rarely need replacement unless they crack or rust, but wood will eventually rot and need to be pulled out and replaced.

Common mistakes to avoid

Cutting straight down instead of at an angle makes the edge unstable—soil crumbles back into the trench and the edge collapses within weeks. Always tilt your blade. Cutting too shallow (less than 2 inches) leaves the edge weak and lets grass roots push through quickly. Cutting too deep (more than 4 inches) wastes effort and can damage tree or shrub roots if they are close to the surface.

Installing edging too low (flush with the soil) lets mulch spill over the top. Install it so the top edge is 1 to 2 inches above ground. Forgetting to stake plastic or metal edging lets it shift and buckle as you add mulch or as the ground settles. Stake every 2 to 3 feet, not just at the corners. Finally, edging in very wet soil or very dry soil is harder than edging in moist soil—wait for a day or two after rain, or water the area the night before if the ground is hard.

Frequently Asked Questions

How deep should I cut the edge?

Cut 2 to 4 inches deep. Deeper is not better—it wastes effort and can hit tree roots. Shallower than 2 inches leaves the edge weak. In loose, sandy soil, 2 inches is usually enough. In clay or compacted soil, go to 3 or 4 inches for a more stable edge.

Can I edge in winter or does it have to be spring?

Spring and fall are best because the soil is moist and workable. Winter soil is often frozen or waterlogged. Summer soil can be hard and dry. If you must edge in winter, wait for a thaw and do it when the ground is not frozen. If you must edge in summer, water the area the night before.

Do I need to remove the old grass before I edge?

No. Your spade cuts through grass and soil at the same time. The grass on the lawn side of the cut stays in place; the grass on the bed side gets buried under mulch or removed when you clean out the bed. You do not need to strip sod first.

How long does a cut edge last without edging material?

A cut edge stays clean for 4 to 8 weeks, depending on soil type and how much rain you get. After that, grass creeps back in and mulch settles. Refresh it in spring and midsummer to keep it sharp all season. With physical edging, the edge lasts 5 to 20 years depending on the material.

What is the best edging material for a curved bed?

Plastic edging bends easily and works well for curves. Metal edging also bends but is stiffer and harder to curve smoothly. Wood edging does not bend and is best for straight lines or very gentle curves. For tight curves, a cut edge with no barrier is often the simplest choice.