Order of work
- Call 811 (in the US) a few days before you dig an edging trench, so buried cables and pipes get marked. Lawn irrigation lines often run along bed edges, so find them before you dig.
- Weed and clear: pull weeds with their roots, cut back dead growth, and rake out the old mulch if you’re replacing it. Rake mulch you keep to break up matted layers.
- Cut the edge: mark the line with a hose or string and cut it with a half-moon edger or flat spade. Dig the trench for plastic edging or a paver strip now.
- Install the edging: set plastic edging in its trench and stake it every 4 ft at an angle, or lay the pavers end to end on the sand bed, flush with the lawn. Backfill and tamp the soil on the lawn side.
- Add compost: spread it over the bed and keep it off stems; in annual beds, fork it into the top 6–8 in.
- Lay the barrier if you use one: wet cardboard overlapped 6 in, or fabric overlapped 6 in, stapled and cut around plants.
- Spread the mulch to the depth in the plan, keeping it at least 4 in away from trunks and stems. Water it in.
Tools you’ll need
- Half-moon edger or a flat spade
- Garden hose or string to mark the line
- Bow rake, mulch fork and wheelbarrow
- Rubber mallet (stakes, pavers) and a tamper
- Utility knife for fabric or cardboard
- Gloves and knee pads
About this planner
Refreshing a garden bed sounds like one trip for mulch, but a proper job has a longer list: how much mulch to add on top of what’s already there, compost for the soil underneath, edging and the stakes or pavers that hold it, and maybe fabric or cardboard to stop weeds. This planner works all of it out from your bed’s shape and size, prices every line, compares bags with a bulk delivery and draws the bed and a section through its edge to scale.
It follows university extension guidance: mulch 2–4 in deep in total (so it only tops up what’s there), about 1 in of compost under the mulch around shrubs and perennials or 2 in worked into annual beds, and mulch kept a few inches away from stems and trunks.
How to use it
- Pick the shape and enter the length and width. For a bed along the house, the length runs along the wall; the planner leaves that side unedged.
- Measure the old mulch with a trowel and choose whether to top it up or rake it out. Then pick the depth you want when you’re done.
- Choose compost, a weed barrier and the edging. Plain mulch with no barrier is the extension services’ advice for plant beds.
- Open Your local prices, enter your store’s prices, and print the project sheet.
How the quantities are worked out
Area: rectangle = length × width; oval = π × length × width ÷ 4;
half oval along a wall = π × length × width ÷ 4 (width = depth from the wall)
Edge: free rectangle = 2 × (length + width); along a wall = length + 2 × width;
oval = π × [3(a + b) − √((3a + b)(a + 3b))] with a, b = half the length and width
Mulch to add = area × (depth wanted − old mulch kept), or the full depth if you remove it
Compost = area × 1 in (top-dressed) or 2 in (worked in)
Bags = cu ft ÷ bag size, rounded up; bulk = cu yd rounded up to the ½ yd, + 1 delivery
Plastic edging = edge ÷ 20 ft coils; stakes = 1 every 4 ft (+1 at the end of an open run)
Paver strip = edge ÷ 8 in × 1.05; sand = edge × 4 in × 1 in × 1.10 in ½ cu ft bags
Fabric = 4 ft strips along the length, overlapped 6 in; staples every 3 ft on the outline and seams
Sources: mulch 2–4 in deep, composted mulch 2–3 in and coarse mulch 3–4 in, at least 4 in from trunks, and raking old mulch instead of adding more, from University of Illinois Extension (Proper Mulching Techniques); 1 in of compost under 2–3 in of mulch around shrubs, and about 2 in worked 6–8 in into flower beds (more at once may encourage grubs), from Virginia Cooperative Extension (426-704). Plastic edging goes in a 4 in trench with a stake every 4 ft (Vigoro’s instructions). Fabric overlaps follow Johnny’s Pro 5 weed barrier instructions (at least 6 in, staples every 5 ft, closer in wind); the planner staples every 3 ft because bed edges get walked on. The oval’s edge uses Ramanujan’s approximation. Mulch and soil quantities match our mulch calculator, and the paver bed matches the paver patio planner.
Worked example
These are the planner’s starting values and the results they produce:
| Bed shape | Rectangle along a house or fence (edged on 3 sides) |
|---|---|
| Bed length | 20 ft |
| Bed width | 5 ft |
| Old mulch in the bed now | 1 in |
| The old mulch | Keep it: rake and top up |
| Mulch depth when done | 3 in – most beds |
| Compost | 1 in on top, under the mulch (shrubs and perennials) |
| Weed barrier | None: mulch alone (best for plant beds) |
| Edging | Plastic coil edging, staked |
| Buy the mulch and compost | Whichever is cheaper |
| Compost bag size | 1 cu ft bag |
| Mulch, per 2 cu ft bag | $4.00 |
| Bulk mulch, per cu yd | $40.00 |
| Compost, per bag | $7.00 |
| Bulk compost, per cu yd | $40.00 |
| Bulk delivery fee | $75.00 |
| Plastic edging, per 20 ft coil | $14.00 |
| Edging stake, each | $0.60 |
| 4 × 8 in paver, each | $0.80 |
| Sand, per 50 lb bag | $6.00 |
| Landscape fabric, per 4 × 50 ft roll | $25.00 |
| Landscape staple, each | $0.15 |
| Bought | Item | Buy | Cost |
|---|---|---|---|
| Plastic lawn edging, 20 ft coils30 ft of edge; join coils with an edging connector | 2 coils | $28.00 | |
| Edging stakesone every 4 ft, plus one at the end, driven at 45° through the edging | 9 | $5.40 | |
| Compost, 1 cu ft bags8.3 cu ft for 1 in | 9 bags | $63.00 | |
| Shredded bark mulch, 2 cu ft bags16.7 cu ft for 2 in on top of the 1 in already there | 9 bags | $36.00 | |
| Estimated materials total | $132.40 | ||
Tips before you buy
- Measure the old mulch before you buy. Mulch breaks down slowly, and beds that get a full 3 in every year end up far too deep.
- Keep mulch at least 4 in from trunks and stems. Mulch piled against bark (“volcano mulching”) is one of the most common causes of tree decline.
- Landscape fabric works best under stone. Under bark mulch, the mulch breaks down on top of the fabric and weeds root in it anyway.
- Leave plastic edging in the sun for a few hours first; it uncoils and lies straight much more easily when warm.
- Bulk mulch is usually cheaper once you need more than about a cubic yard, but the delivery fee makes small jobs cheaper in bags.
- Set a paver strip flush with the lawn so the mower wheel can run on it and you never need to trim the edge.
Frequently asked questions
How much mulch do I need to refresh a bed?
Only the difference between what’s there and 2–4 in. A 20 × 5 ft bed with 1 in of old mulch needs 2 in more to reach 3 in: 16.7 cubic feet, which is 9 bags of 2 cu ft mulch or 0.62 cubic yards. If you rake the old mulch out, a full 3 in takes 25 cubic feet: 13 bags or 0.93 cubic yards.
How much edging do I need for a flower bed?
Measure the sides that touch the lawn. A 20 × 5 ft bed along the house has 30 ft of edge: two 20 ft coils of plastic edging and 9 stakes (one every 4 ft plus one at the end). An oval island bed 12 × 6 ft has about 29.1 ft of edge all around, which takes 8 stakes.
Should I put landscape fabric under mulch?
Usually not in planted beds. Bark mulch breaks down on top of the fabric into a layer where weeds root, and the fabric gets in the way when you add or move plants. Use plain mulch, or cardboard to smother lawn or weeds when you make a new bed; keep fabric for stone or gravel areas.
Is bagged or bulk mulch cheaper?
It depends on the delivery fee. With mulch at $4 per 2 cu ft bag or $40 per cubic yard, compost at $7 per 1 cu ft bag or $40 per yard and a $75 delivery, topping up a 20 × 5 ft bed (2 in of mulch and 1 in of compost) costs $99 in bags and $135 in bulk. A 40 × 10 ft bed with the same layers costs $374 in bags and $235 in bulk.
How many pavers do I need to edge a bed?
Laid end to end, a 4 × 8 in paver covers 8 in of edge, so a foot of edge takes 1.5 pavers, plus about 5% for cuts. A 30 ft edge takes 48 pavers and two 50 lb bags of sand for the 1 in bed underneath.