Which edge does my lawn need?
Pick by how your grass spreads: under the soil, on top only, or in bunches.
| Grass | How it spreads | Edge to pick |
|---|---|---|
| Bermuda grass | Runners on top and rhizomes below, fast | Grass Barrier, standard layout |
| Zoysia | Runners and rhizomes, slower than Bermuda | Grass Barrier, standard layout |
| Kentucky bluegrass | Rhizomes | Grass Barrier if it keeps coming up in beds; otherwise shallow edging |
| St. Augustine, centipede grass | Runners on top only | Shallow edging if you trim along it; Grass Barrier for a taller lip |
| Tall fescue | Bunches, some short rhizomes | Shallow edging is often enough; watch the edge the first year |
| Perennial ryegrass | Bunches | Shallow edging is often enough |
St. Augustine and centipede don't spread under the soil, so a shallow edge can work if you trim along it. Pick Grass Barrier if you want a taller lip to trim against. The standard layout shows 4 in, against about 1 in for a shallow edge.
With no lawn on the other side, such as gravel against mulch, any edge that holds the material in place will do.
Grass Barrier landscape edging by ProTech Plastic is a 10 in tall strip of 100 mil (2.5 mm) HDPE, with 200 lbf puncture resistance (ASTM D4833). The 10 in is its height, not its depth. You choose how much goes below the soil.
How do I tell if my lawn spreads under the soil?
- Dig up a palm-sized plug of lawn at the bed edge, with a few inches of soil.
- Look at the stems. Stems running sideways under the soil are rhizomes. Stems lying along the top are runners (stolons).
- No sideways stems at all? A clump that only widens from its base is a bunch grass.
Your county extension office can also name a sample. If you still can't tell, plan for the deeper edge.
How deep does each edge actually reach?
Depth below the soil is the total height minus what shows above it.
| Edge | Total height | Above the soil | Below the soil |
|---|---|---|---|
| Shallow edging, 4 in | 4 in | 1 in | 3 in |
| Shallow edging, 5 in | 5 in | 1 in | 4 in |
| Grass Barrier, standard | 10 in | 4 in | 6 in |
| Grass Barrier, low profile | 10 in | 2 in | 8 in |
| Grass Barrier, flush | 10 in | 0 in | 10 in |
The shallow rows assume about 1 in shows. Worked example: a 5 in edge with 1 in showing reaches 5 − 1 = 4 in down.
Grass Barrier in the standard layout reaches 10 − 4 = 6 in down. That is 6 − 4 = 2 in deeper than the 5 in edge. Its lip is 4 − 1 = 3 in taller.
When does grass get under shallow edging?
Grass gets under when its rhizomes run deeper than the edge. In undug soil, Bermuda rhizomes are usually 1 to 6 in deep.
A 4 to 5 in edge reaches 3 to 4 in, so it leaves the bottom 2 to 3 in of that layer open.
Rhizomes can run deeper than 6 in where:
- the soil was dug or tilled deeper than 6 in
- the soil is sandy
- they pass under a sidewalk
- they run against a wall or foundation
For Bermuda, keep the standard layout even there. Its 4 in lip is what lets you see and trim runners. Watch the inside of the bed, and dig out any shoot that comes up, rhizome and all.
If new shoots come up a few inches inside the bed and nothing crosses the top, the grass went under. That's a depth problem.
If runners lie over the top, that's a height and trimming problem.
How does the cost compare?
Price both the same way: feet of edge times the price per foot, plus one connecting kit per joint. Shallow edging runs from thin plastic to steel, and prices vary a lot, so compare actual products.
The price per foot drops at 50 ft and again at 100 ft, counting every foot of Grass Barrier in the order. Shipping is free in the lower 48 states. Prices are on the Grass Barrier page. For worked totals, see how cut-to-length ordering works.
Count the redo, too. If grass already gets under your edge, a new edge at the same depth meets the same rhizomes.
Does Grass Barrier bend around curves?
Yes. Let the coil relax in the sun before you set it, so it lies flat and follows the bed line.
- Lay out the line with a garden hose or rope. Use gentle curves.
- Measure along the hose, not straight across. Round up to the next 5 ft.
- Set the strip and firm the soil on both sides, so the curves hold their shape.
Worked example: a round bed 14 ft across has π × 14 = 44 ft of edge. Round up to 45 ft.
That is one piece, with one joint where the ends meet, so one kit. Put the joint where you can reach both sides of the strip to clamp it.
Call 811 before you dig. The full steps are in the Grass Barrier install manual.
How many joints and connecting kits will I need?
You need one Grass Barrier connecting kit per joint. Each kit has two pre-drilled 200 mil HDPE clamps and 316 stainless hardware. Overlap the ends a little inside the clamps. It makes the joint easier to line up, and you don't order extra length for it.
Grass Barrier comes as one piece up to 110 ft, in 5 ft steps from a 20 ft minimum. For a longer run, order more than one cut. Then count joints:
- Two ends, like a path to a fence: joints = pieces − 1.
- Closes on itself, like an island bed: joints = pieces, because the ends meet.
| Job | Feet of edge | Cuts | Joints and kits |
|---|---|---|---|
| Long border with two ends | 180 ft | Two 90 ft | 1 |
| Large bed edged all the way around | 150 ft | Two 75 ft | 2 |
For the border: 180 ÷ 110 = 1.6, so round up to 2 cuts, with 2 − 1 = 1 joint. For the bed: 150 ÷ 110 = 1.4, so 2 cuts, and the ends meet, so 2 joints.
For more bed sizes, including short runs under the 20 ft minimum, see how to keep Bermuda grass out of flower beds.
Do I need Edge Guard?
No. Grass Barrier works without it. Edge Guard is an optional cap that fits over the top edge, sold in 22 ft lengths.
It smooths out waves, makes the top edge look thicker and more finished, and makes the edge a little safer to brush against. It doesn't change how deep the barrier reaches. See the Edge Guard page for the price.
Who is Grass Barrier not for?
- Bamboo. Most running-bamboo rhizomes stay in the top 12 to 18 in of soil, deeper than a 10 in strip reaches. Use Bamboo Shield, 24, 30 or 36 in deep. Most clumping bamboo needs no barrier; see running vs clumping bamboo.
- Tree roots near paving. Use Sidewalk Shield, 18, 30 or 36 in deep.
- A bed already full of Bermuda. An edge keeps new grass out. It won't remove grass already inside. Clear the bed first, as in how to keep Bermuda grass out of flower beds.
- Grass and weeds from seed. No edge stops seed. That's a weeding job.
Common mistakes
- Setting it flush next to Bermuda. With nothing above the soil, runners can cross the top and root in the bed before you notice.
- Leaving a joint unclamped. Join every joint with a Grass Barrier connecting kit.
- Leaving trimmings on the bed. Cut pieces of Bermuda runners and rhizomes can root again in moist soil. Rake them up.
FAQ
Can I just set my 4 or 5 in edging deeper?
Only by giving up the lip. A 5 in edge set flush reaches 5 in down. That is 6 − 5 = 1 in short of the 6 in that Bermuda rhizomes usually reach in undug soil. With nothing showing, runners cross the top. Grass Barrier's standard layout gives 6 in below and a 4 in lip.
Can grass still get over a 10 in barrier?
Yes. Runners can climb over the top edge, so trim along the outside of the edge when you mow or edge the lawn. The barrier works below the soil. On a 4 in or 2 in edge, keep mulch from building up over the top edge, so runners can't bridge across it.
Will 4 in of black edge look bad?
If you'd rather see less, use the low profile layout, with 2 in above the soil, or set it flush, with none showing. A lower edge gives runners an easier path over the top, so plan to trim more often. Next to Bermuda, use the standard layout with 4 in showing.