There is a moment on a walk through the neighbourhood when two gardens look almost identical and still feel completely different. Both lawns have patches of moss, both borders have run out of shape by July. One looks cared for, the other does not. The difference is not in the open lawn, it is in the last five centimetres at the edge.
A crisp edge is the cheapest trick in garden design. It costs you an hour twice a year and does more for the look than a round of fertiliser. So, in order: why cutting the edge twice a year is enough, which tools you need in between, and why a row of stones laid flush with the lawn abolishes the trimming rather than just shortening it.
At a glance
- The edge creates the impression, not the lawn itself. A mediocre lawn with a sharp edge looks better kept than a good one with a frayed rim.
- Two cuts a year are enough if you tidy up in between. Late March to mid April · CW 13 to 16, and late August to mid September · CW 36 to 38. In between you only trim.
- Vertical does half the work. The blade goes straight down, 5 to 8 cm deep. An edge cut at an angle collapses with the first heavy rain.
- A mowing edge removes the trimming altogether. A row of stones flush with the lawn, at least 15 cm wide, that the mower can run one wheel along, makes the trimmer and the edging shears redundant.
- Plastic edging is the most expensive cheap solution. Around 2 to 8 € per metre and brittle after five to ten years. Metal and stone last for decades.
Why the edge carries the whole impression
Grass does not only grow upwards, it also grows sideways. Smooth meadow grass pushes out underground rhizomes, creeping bent runs above ground with stolons, and where couch grass sits in the border it travels anyway. Perennial ryegrass, the main component of most lawn mixtures, grows in tufts and only creeps slowly over the rim. So the travelling is down to the runners, not to the bulk of the lawn. A border without a clear separation is not a border as far as the grass is concerned, it is soft soil without competition. After two years the bed stands 15 cm narrower than planned, and because it happens so slowly you barely notice it in your own garden and spot it instantly next door.
When the edge wanders off
Between the kerb stone and the green there is a gap here that nobody planted. It appears because the mower cannot cut cleanly against the stone, the trimmer shaves off what is left, and the soil next to hot concrete dries out faster than the open lawn.
Repairs only work from the grass side: loosen the soil, work in a little compost, then overseed in spring or from late August · CW 35 to 38 with fresh seed. Overseed alone and you will be looking at the same picture next summer.
Cutting the edge: get it right once and it holds
The classic tool is the half moon edging iron, a semicircular blade on a long shaft with a tread. If you do not own one, use a spade. More important than the shape is the sharpness: a blade touched up with a file works twice as easily as one that has been hanging blunt in the shed.
Start a day after rain
Moist soil cuts, dry soil breaks. In a dry spell, water the edge the evening before, otherwise you will be tearing instead of cutting.
Make the line visible
On straight runs use two pegs and a taut bricklayer's line, one or two centimetres above the grass. For curves, lay out an old garden hose, step back a couple of paces and check whether the curve flows. Curves cut freehand look accidental, laid out ones look intentional.
Cut vertically, one cut against the next
Blade against the line, held vertically, then press down evenly with your foot. 5 to 8 cm is plenty for the look. Where runners have gone well into the border, go 10 to 15 cm deep. Overlap the cuts by two fingers' width, otherwise you leave little teeth standing.
Lift out the wedge
Second cut, angled from the border side towards the first one. The wedge of soil in between lifts out in one piece. What remains is a vertical wall of turf with a shallow groove behind it. That groove is the actual point: it is the threshold the runners cannot cross.
Clear the spoil, then finish the edge
Clean turves can go on the compost heap upside down, grass side down. If there is couch grass in them, it will survive a cold garden heap and come back into the border with the compost, so let those turves dry out first or put them in the green waste. To finish, take off the overhanging blades with edging shears.
Leave the groove open, do not fill it in
Plenty of people fill the groove behind the edge with bark mulch straight away because it looks tidier. That removes the barrier, and the runners simply carry on through the mulch. Two centimetres of air hold back more grass than five centimetres of mulch.
Late March to mid April · CW 13 to 16 the soil is moist and the lawn is not yet in full swing, so the cut holds into the summer. The second date falls late August to mid September · CW 36 to 38, once the heat has passed and the soil holds water again. In August itself the job is only worth doing after rain: in a dry summer the turf breaks instead of cutting. In October you can still make corrections, but not deep ones, because open soil does not like going into the frost.
In between: shears, trimmer and the rest
Between the two cutting dates the edge is only tidied up, four to six times over the season, each time straight after mowing.
What the cordless trimmer can do, and what it cannot
A trimmer is fast and unbeatable for long runs along a fence. But it does not cut, it beats. Hold the line vertically against the border and drop it too low, and you mill away the turf and expose bare soil. That is exactly how the bald strip appears.
For the last few centimetres along a border, edging shears with vertical blades are more precise and much quieter. Ten metres of edge take a few minutes, and the turf stays intact.
Trimmers and young trunks do not get along
The line damages the bark on young trees reliably, often all the way round the base of the trunk. What it hits is bark, phloem and cambium, the layer directly under the bark that carries the sugars from the leaves down to the roots. Once that ring is severed all the way round, the roots starve. You see the wound straight away, the decline only one or two years later. A ring of mulch takes the opportunity away from the line.
Trimmers face tighter hours than the mower
German noise law treats brushcutters, grass trimmers and edge trimmers more strictly than lawnmowers: in residential, spa and recreational areas the 32nd BImSchV allows them on working days only from 9 to 13 and from 15 to 17, and not at all on Sundays and public holidays. A lawnmower may run there from 7 to 20 on working days, and again not on Sundays or holidays. So if you want to tidy the edge right after mowing, both jobs have to fit into the same window. In Austria and Switzerland the quiet hours are set by cantons and municipalities, usually including a midday break. Hand shears you may use whenever you like.
The mowing edge: the trick that abolishes trimming
Everything described so far is maintenance. A mowing edge is construction, and it is the only measure after which the trimming disappears entirely. The principle is unspectacular: a row of stones, laid flush with the lawn, wide enough for one wheel of the mower to run along. The width matters just as much as the height. Below 15 cm it gets tight, and for a robotic mower 20 to 25 cm is the safe number. In practice that means flat laid edging stones, block paving in a 20 × 20 cm format, or two rows of setts. A single row of 8/11 cubes is a separation, not a mowing edge you can drive on.
The height is what decides it. The stone sits flush with the lawn or at most a centimetre below, never above. One centimetre too high and the cutting deck strikes it. Two centimetres too low and the grass grows over the stone, which puts you back with the trimmer.
Dig the trench
Set the line with a string, then dig to the width of the stone plus 10 cm. Work out the depth from the lawn surface downwards: stone height plus 5 cm concrete bed plus 15 to 20 cm of crushed stone. With an 8 cm block paver that comes to 30 to 33 cm. Before you start, think about where the irrigation pipes, the garden power cable and the robotic mower's boundary wire run. This calculation separates the edge that lasts ten years from the one that ripples after the second winter.
Lay and compact the sub-base
Fill in 15 to 20 cm of crushed stone, grading 0/32, and compact it in layers with a hand tamper. Without that layer water stands under the stone, freezes and lifts the whole row. On clay you want a separating fleece between soil and crushed stone, otherwise the sub-base silts up within a few years.
Set the stones in concrete
On top of the crushed stone goes a bed of lean concrete, roughly 5 cm thick. Lay the stones along the string and tap them down to height with a rubber mallet. Only ever set as many as you can manage before the concrete starts to go off.
Add the back support
On the border side, a haunch of lean concrete goes against the stone, roughly halfway up its height. It holds against the pressure of the soil and against the mower's wheel. This support is almost always left out, and then the row tips towards the border sooner or later.
Finish off and leave it alone
Close the joints with jointing sand, backfill soil flush on the lawn side, then stay off it for 24 to 48 hours. Wait about a week before you take the mower over it, because until then the back support has not reached its load capacity. Below 5 °C, or with frost in the forecast, do not concrete at all.
An edge the mower can drive along never needs trimming. Every other edge is follow-up work you have built for yourself.
Gartenkern
Permanent edgings compared
Not every edging is a mowing edge. A metal strip separates lawn and border reliably, but the mower cannot run on it because it is only millimetres wide. If you want to be rid of the trimming, you need width.
Five edgings compared
- Metal strip in weathering steel, aluminium or galvanised steel
The most elegant separation, because once installed it almost disappears. Weathering steel takes on an even rust patina, aluminium stays matt grey and bends into curves more easily, and galvanised steel is the budget option with its cut edges as the weak point. Material runs around 4 to 10 € per metre for galvanised steel and aluminium, and 12 to 20 € for weathering steel. From 2 mm sheet thickness it lasts decades; the widespread 1.2 mm strips are consumables. Worth knowing: the weathering patina only forms where wet and dry alternate, so the buried part keeps corroding. Look for a folded or rolled top edge as well, because sharp cut strips are a cutting hazard for bare feet. Against pale paving, choose aluminium: weathering steel sheds rusty water in its first months, and that stains light slabs.
- Plastic edging
Cheap, laid in an hour, around 2 to 8 € per metre. And the version that comes back out fastest. UV light makes the plastic brittle after five to ten years, frost lifts the strip out of the ground, and then a wavy rim stands above the lawn. If you must, use ground pegs every 30 cm.
- Row of pavers flush with the lawn
The only solution here that genuinely abolishes trimming, provided the row gets its 15 to 25 cm of width. Block paving and edging stones cost roughly 3 to 15 € per metre in material, granite setts 18 to 30 €. Set in concrete by a contractor, expect around 20 to 45 € per linear metre for concrete stones and 40 to 90 € for granite, plus a flat 80 to 200 € for travel and spoil disposal. Swiss rates sit clearly above the German ones, so get quotes in francs there.
- Bricks set on edge
The classic in cottage and front gardens, warm in tone and lovely against brickwork. On edge you need eight to ten bricks per metre, around 10 to 25 € in material. The type matters: paving bricks rated for ground use and frost. Soft fired reclaimed bricks and backing bricks from a demolition site take frost damage after two or three winters, and their surface flakes off in shells. Even frost resistant facing brick is made for a vertical wall, not for ground contact with standing water and wheel loads. On edge, brick makes a handsome separation, but at around 11 cm wide it is not a mowing edge.
- Timber palisade
Ready made units with pointed ends can be driven in without a trench, around 5 to 15 € per metre. Pressure treated pine in use class 4 lasts 10 to 20 years in ground contact, thin budget palisades a good deal less. Robinia manages 20 years and more without any treatment, oak sits in between. The treatment works with copper salts, so right next to a vegetable bed pick untreated robinia or oak instead. Timber moves, so the line will never stay perfectly straight. In a naturalistic garden that is precisely the appeal.
Frost lifts anything that is not drained
Almost every edging that heaves or tips fails at the same point: water stood underneath the material and froze. Concrete, brick, metal and plastic all buckle alike. The crushed stone sub-base decides the service life, and on heavy clay soils go for 20 cm rather than 15 cm. More important than the thickness, though, is that the water can get away: with a fall towards the lower point, or connected to a drain. A sealed trench of crushed stone in clay is not a sub-base, it is a bathtub.
Living edges and the bigger picture
Not every boundary has to be stone. A row of box (Buxus sempervirens) is the classic border edging in a cottage garden. It looks good, but it will not stop the runners. Newly planted, box is also the riskiest option on this list in 2026: box tree moth and box blight are widespread across central Europe and will strip a clipped edging within a few years. If you want the form without the vigilance, take Japanese holly (Ilex crenata), dwarf spindle or box honeysuckle. Box is also toxic in every part, which is an argument where children play on the lawn. Lavender along a sunny south facing edge and lady's mantle in part shade make softer transitions, but they still need a cut edge behind them. The sensible answer is the combination: the barrier at the back, the plant at the front.
And an edge that frays constantly is rarely an edge problem. Where the lawn pulls back along a path, care in hot weather helps more than any amount of trimming. If you want the wider frame, paths and border edgings has the whole picture.
Seen from the robotic mower, a mowing edge pays twice
A robotic mower does not cut right to the rim, because its blade sits inside the wheel track. A flush row of stones moves exactly that limit: the robot runs one wheel on the stone, so the blade reaches the very edge of the turf. The condition is a height difference of no more than one centimetre. Only then may the boundary wire on cable models run right up to the stone; with a taller rim the manufacturers ask for around 30 cm of clearance, and the robot no longer reaches the edge at all. On wireless RTK models you set the area up accordingly in the app. Depending on blade geometry a narrow uncut strip can remain.
Cutting the edge is one of those jobs that costs you an hour twice a year and works for you the rest of the time. Jobs like that are the ones that slip most easily, because the gap between the two dates is so long. Note in your garden journal when you cut and how long the edge held. After two summers you will see where the cut is enough and where a row of stones is worth it.
Common questions about lawn edges
When should you cut a lawn edge?
Twice a year is enough: late March to mid April · CW 13 to 16, when the soil is moist and the lawn is not yet in full growth, and late August to mid September · CW 36 to 38, once the heat has passed. Cut a day after rain or after watering, and the blade goes through the turf easily. In between you only tidy up with shears or a trimmer. Where a well fed border adjoins, or couch grass sits in it, you will also want a short touch up cut every six to eight weeks.
How deep should you cut a lawn edge?
For a clean look, 5 to 8 cm straight down is plenty. Where grass has already run well into the border, go 10 to 15 cm deep, because that is where the shallow runners sit that would otherwise shoot again within weeks. More important than the depth is the angle: an edge cut at a slant breaks off with the first heavy rain.
What is the difference between a lawn edge and a mowing edge?
A lawn edge is any separation between lawn and border or path, including a narrow metal or plastic strip. A mowing edge is a special case of it: it sits flush with the lawn and is wide enough, at least 15 cm and for robotic mowers better 20 to 25 cm, for the mower to run one wheel along. A lawn edge holds the line but you still have to trim. A mowing edge makes that unnecessary.
How much does a mowing edge cost per metre?
Material is the smaller item: block paving or edging stones come to roughly 3 to 15 € per linear metre, granite setts 18 to 30 €, plus a few euros for crushed stone and lean concrete. Doing it yourself, you usually stay under 25 € per metre. Set in concrete by a contractor, 20 to 45 € per linear metre is normal for concrete stones and 40 to 90 € for granite, plus a flat 80 to 200 € for travel and spoil disposal. Laid in a plain sand bed it comes cheaper but does not take frost as long. Swiss quotes sit clearly above the German ones.
Which lawn edge lasts longest?
Stone in concrete, by a clear margin. A row of pavers or granite on a compacted sub-base with a lean concrete back support survives decades and copes with frost, mower wheels and children's bikes. Metal from 2 mm sheet thickness comes next. Timber palisades give way after ten to twenty five years depending on the species, treated pine at the lower end and robinia at the upper. Plastic edging is the shortest lived of all.
Is a spade good enough instead of an edging iron?
On straight runs a sharp spade is just as good. In curves its straight cutting edge leaves small facets that read as an angular curve from a distance, while the semicircular blade of an edging iron runs through smoothly. What matters more than the tool is the cutting edge: one pass with a file and the work halves.
Sources and further reading
- Mowing your lawn properly
- Overseeding bare patches in the lawn
- Laying garden paths and border edgings
- Lawns in summer heat and drought
- Plant profiles: box · lavender · lady's mantle
- 32. BImSchV, the German equipment and machinery noise protection ordinance on operating times for trimmers, brushcutters and mowers
- Forschungsgesellschaft Landschaftsentwicklung Landschaftsbau (FLL), German codes of practice for paving beds, sub-bases and bedding material
- DIN EN 350 on natural durability classes of wood, plus the use classes in DIN 68800 for pine, oak and robinia in ground contact
- Deutscher Holzschutzverband, guidance on pressure treatment and use class 4
Legal note
The operating times given reflect the current state of the 32nd BImSchV for Germany and are not a substitute for legal advice. Municipal by-laws, allotment rules and tenancy agreements, as well as the regulations in Austria and Switzerland, may be stricter. Prices are indicative figures for Germany and vary by region; only a written quote is binding. If in doubt, ask your local authority.
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