Key takeaways
- A half-moon iron cuts the edge. Long-handled shears keep it tidy
- Cut 7-8cm deep, with the blade upright against a plank or hosepipe
- Re-cut once or twice a year, mainly in March or April
- Shear every two to three weeks while you're mowing
- Keep the gutter clear so grass can't creep into the border
A crisp edge makes the whole garden look smarter, and it’s one of the easiest lawn jobs going. You need the right tool, a good straight cut once or twice a year, and a quick trim every few weeks.
Which lawn edging tool do you actually need?
Three tools cover every edging job, and they split into two jobs: cutting the edge and keeping it tidy.
A half-moon edging iron is the cutting tool. Its curved blade slices a clean, upright face through the turf and roots. You only need it once or twice a year, and nothing else cuts such a clean line.
A border spade is the stand-in most people already have. It works, but the blade is slightly dished, so the line curves a little with every cut. Press it against a plank to keep it straight.
Long-handled edging shears are the tidying tool. The blades sit at right angles to the handles, so you can trim grass hanging over the edge while standing up. They cut grass, not soil.
Cut with the iron. Tidy with shears or a strimmer. Mixing up the two jobs is why so many edges fail.
The edging kit: a half-moon iron for cutting, long-handled shears for tidying and a border spade as a stand-in.
How to cut a crisp lawn edge step by step
Pick a day in March or April when the soil is moist but firm. If it squelches, it will smear rather than slice, just like the rule for mowing a wet lawn.
- Mark your line. Lay a plank along straight edges. For curves, use a hosepipe that’s been warming in the sun for a bit so it bends and stays put.
- Cut straight down. Hold the half-moon blade upright against the plank and push it in 7-8cm with your boot. An upright face holds together far better than a sloping one.
- Overlap each cut a little, so you get one smooth line rather than a row of bites.
- Clear the gap. From the border side, lift out the cut turf and loose soil with a trowel. You want an open gutter, not a filled-in trench.
- Add a back-cut if you like. A second, sloping cut from the border side widens the top of the gutter, so soil falls away from the lawn edge rather than against it.
The first cut takes a while. After that it’s much quicker, because you’re only refreshing the line.
A firm push with the boot drives the iron 7-8cm down. The plank keeps the line straight.
How often should you edge a lawn?
Re-cutting is a once or twice a year job. The main one is in March or April, when the soil is moist and the grass is starting to grow. A light second cut in September repairs summer wear, but you can skip it if the edge still looks good.
Shearing is little and often: every two to three weeks from April to October, ideally straight after you mow. Tie it in with when to mow the lawn and it soon becomes habit. Grass grows fast over the edge in early summer, so a month off soon blurs that crisp line.
A quick trim with long-handled shears keeps the line sharp between re-cuts.
Permanent lawn edging materials ranked
If you’d rather not re-cut every year, a permanent edge does the job for you. Steel strip lasts the longest and you can mow straight over it. Timber gravel board is cheaper but rots in time. Plastic is cheap too, but frost can lift it so the mower catches it. Brick mowing strips look smart and carry the mower wheel neatly. Whatever you choose, set it level with the grass or just below.
Steel strip set level with the turf. The mower wheel rolls straight over it.
Why lawn edges break down
A cut edge is a gap in a living mat of grass, and the grass spends all season trying to close it. Here’s how it happens.
- First few weeks: roots reach the cut. Fine roots grow into the bare face, but nothing shows yet.
- Over the summer: grass creeps across. Some grasses spread by underground runners, others by runners along the surface. Both creep into the border and root as they go.
- Winter: frost. Water in the soil freezes and thaws, lifting and crumbling the cut face. By March the crisp edge has slumped.
- All season: mower scalping. A mower wheel dropping off a slumped edge tips the deck and scalps a bare strip, which weeds love. A blunt blade makes it worse, so see our guide to sharpening a mower blade. Fix scalped patches the same way as any thin area, as in fixing a patchy lawn.
The big mistake is thinking shears do the whole job. Shears only cut the leaves. They never reach the runners creeping underneath. Only a full-depth re-cut stops those, which is why a sheared-but-never-recut edge still lets grass into the border.
Left: a well-kept edge with an open gutter. Right: a neglected edge, slumped and with grass creeping into the bed.
Edge care month by month
Edges follow the lawn’s growing year, so it’s quiet in winter and busy from April. The September jobs fit nicely with autumn scarifying and aerating.
| Month | Edge job |
|---|---|
| January | Keep off frosty edges. Check plastic or timber strips for frost lift |
| February | Clean tools and sharpen the half-moon blade with a file |
| March | Main re-cut: 7-8cm deep, blade upright, soil moist but firm |
| April | First shear of the year. Clear winter soil out of the gutter |
| May | Shear every two to three weeks |
| June | Shear every fortnight. Check edging strips still sit level |
| July | Shear every two to three weeks. Look for cracks along the edge in dry spells |
| August | Shear, and straighten any wobbly strimmer lines against a plank |
| September | Re-cut damaged bits if needed. Last full round of shearing |
| October | Final shear. Rake leaves out of the gutter |
| November | Clear the gutter again. Don’t tread on the edge in wet weather |
| December | Stay off the lawn. Check edging after hard frosts |
Stop grass invading your borders for good
Keeping grass out is about three habits, not one purchase. Keep mulch a little below the top of any edging strip. Clear the gutter whenever soil or leaves fill it, which takes seconds while you’re shearing. And re-cut to full depth each spring, so anything that crept across in summer gets cut off. Do those three and your border stays clean, whatever edging you have.
The gutter from the side: an upright face on the lawn side and a sloping back-cut that grass can’t bridge.
Common mistakes with lawn edging
- Edging soggy ground. Wet soil smears and the edge slumps within weeks. Wait until a handful of soil crumbles in your hand.
- Cutting too shallow. A shallow cut looks fine for a month, then grass sneaks underneath. Go 7-8cm deep every time.
- Plastic edging sitting too high. Anything above the grass catches the mower and gets pushed up further by frost. Set it level or just below.
- Letting the gutter fill in. A filled gutter is a soil bridge for roots. Keep it raked out.
- Shearing for years without re-cutting. The edge looks tidy on top while it crumbles underneath. A spring re-cut keeps it sharp.
A crisp edge is the cheapest upgrade a lawn can get, and a few minutes every couple of weeks keeps it that way. Fit the jobs above into your year with our UK lawn care calendar, or browse the how-to section for more practical guides.
Frequently asked questions
What is the best tool for edging a lawn?
A half-moon edging iron gives the cleanest, longest-lasting edge. Use it to re-cut the edge once or twice a year. Long-handled shears then keep it tidy every two to three weeks. A border spade will do at a push, but its curved blade makes the line wander.
How often should you edge a lawn in the UK?
Re-cut once or twice a year, and shear every two to three weeks. Do the main re-cut in March or April while the soil is moist. Shearing runs through the mowing season, roughly April to October, and only takes a few minutes.
How deep should a lawn edge be?
About 7-8cm deep, with the blade held upright. Shallower cuts let creeping grass roots sneak underneath into the border. You can add a sloping second cut from the border side to widen the top of the gutter. Re-cut to full depth once or twice a year.
Can you mow over lawn edging?
Yes, if it sits level with or just below the grass. Steel strip and brick mowing strips both let a mower wheel run straight over. Timber works if it’s set level with the lawn. Plastic edging often sits too high, so the blade catches it.
What is the cheapest permanent lawn edging?
Timber gravel board is usually the cheapest. It does rot in time, though. Recycled plastic costs about the same, but frost can lift it. Steel costs more but lasts far longer and you can mow straight over it.
Why does my lawn edge keep collapsing?
Shallow cuts, frost and creeping grass are the usual culprits. Grass sends runners into the border every season, and winter frosts crumble the cut face. A 7-8cm deep gutter, re-cut each spring, deals with all three.
Our team produces practical UK gardening guidance from source research, contributor records and established horticultural practice. Editorial standards are overseen by Matt W.
