Enter the area and choose the job. We’ll set a practical depth and tell you how much mulch to order.
Mulch depth is one of the few gardening numbers with a hard ceiling. Two to three inches suppresses weeds, holds moisture and moderates soil temperature. Four inches and beyond starts causing the problems mulch is supposed to prevent.
Thick mulch sheds water rather than admitting it. A deep layer of fine shredded material mats down and forms a crust that light rain never penetrates, so the soil underneath dries out while the surface looks perfectly damp. Deep mulch also stays waterlogged at the bottom, which suffocates the shallow feeder roots living in the top few inches of soil.
Around a shrub or perennial, 2 inches is plenty. Open beds and around trees can take 3. Coarse bark nuggets tolerate the upper end better than fine shredded mulch because they do not mat.
Topping up an existing bed is not the same as mulching a new one. Rake back what is there and measure — if you already have 2 inches, adding 2 more gives you 4 and the problems above. Often the right answer is to fluff the existing layer with a rake and buy nothing.
Shredded hardwood is the default: cheap, widely available, knits together so it stays on slopes, and breaks down into the soil within a season or two. That breakdown is a feature in a planting bed and a nuisance where you wanted a permanent surface.
Bark nuggets last longer and drain better, but being chunky and light they float and wash off any real slope. Pine straw is the southern standard, extremely light, and excellent on slopes because the needles knit together.
Cedar and cypress resist decay longest and carry some insect-repellent reputation. They also cost more and break down too slowly to improve the soil much.
Dyed mulch is usually recycled wood coloured with iron oxide or carbon black. The dye itself is not the concern; the source wood can be, since some of it is reclaimed construction timber. Buy from a supplier who can tell you what is in it.
Rubber mulch does not decompose, which sounds like an advantage until you want to change the bed. It is a reasonable playground surface and a poor garden one — it adds nothing to soil and is difficult to remove.
A cubic yard is 27 cubic feet, so it takes 13.5 of the standard 2 cubic foot bags to make one yard. At $4 a bag that is about $54 per yard in bags, against roughly $30 to $45 per yard bulk before delivery.
With a $50 to $75 delivery charge, bulk wins at about 3 cubic yards and up. Below 2 yards, bags usually cost less all-in and save you owning a tarp and a wheelbarrow afternoon.
The other consideration is your driveway. Bulk mulch arrives as a pile that has to go somewhere for a day or two, and it stains concrete. Bags do not, which is sometimes worth the premium on a small suburban lot.
Mulch heaped into a cone around a tree trunk — volcano mulching — is the single most common and most damaging mulching mistake, and it is everywhere in commercial landscaping.
Bark is not root tissue and is not built to sit wet. Held against the trunk it stays damp, softens and rots, and the tree loses the barrier that keeps pathogens out. Worse, roots grow up into the moist mulch and circle the trunk instead of spreading outward, eventually strangling the tree they belong to. The damage takes years to show and is usually fatal by then.
Keep mulch 3 to 6 inches clear of the trunk and spread it wide instead — ideally out to the drip line. A wide, flat ring of mulch does everything a deep pile was supposed to do and none of the harm.
Most beds need topping up once a year, usually in spring, and the amount is far less than a full application. Hardwood mulch loses roughly an inch a year to decomposition.
Before buying, rake the existing layer. Mulch that has matted and crusted often looks thin while still being 2 inches deep — loosening it restores appearance and function for free. Fresh mulch over a compacted old layer just deepens the mat.
Every three or four years it is worth pulling some of the accumulated layer out entirely rather than adding to it, particularly in beds that never seem to dry out.
Volume is area multiplied by depth. Weight is that volume multiplied by the material's density.
volume = area × depth
tons = volume (cu ft) × 30 lb/cu ft ÷ 2000
order = volume × 1.05Density used: 30 lb per cubic foot. Shredded hardwood mulch. Bulk mulch runs 400–1,200 lb per cubic yard depending on type and how wet it is; 30 lb/ft³ (810 lb/yd) is a mid-range dry figure. Actual delivered weight varies with moisture and stone size, so treat tonnage as an estimate and confirm with your supplier.
The recommended order adds 5% on top. Material settles, ground is never perfectly flat, and a second delivery costs far more than a little extra mulch.
Bag count assumes 2 cu ft bags, rounded up to whole bags.
About 14 bags at the common 2 cu ft size, since a cubic yard is 27 cubic feet. At 3 cu ft per bag it is 9 bags. Bulk delivery is usually cheaper than bags past about 2 cubic yards.
2 to 3 in on established beds. A new bed with no existing mulch wants 4 in, or up to 6 in where weeds are bad. More than that starts blocking water and air from reaching roots.
324 sq ft at 1 in deep, 162 sq ft at 2 in, 108 sq ft at 3 in, and 81 sq ft at 4 in. Those are the four numbers worth remembering, and the calculator above works out anything in between.
Anywhere from 400 to 1,200 lb depending on the type and how wet it is. Moisture is the biggest factor — mulch that has sat through a rainstorm can weigh nearly double its dry weight, which matters if you are hauling it in a pickup.
Bags win for small beds, awkward access, or when you cannot take delivery. Bulk wins on price past roughly 2 cubic yards, which is about 14 bags. Bulk also arrives without 14 plastic sacks to dispose of.
Once a year for most wood mulches, because they break down into the soil — which is a feature, not a fault. Measure what is still down and add only the difference to get back to 3 in, rather than piling a fresh 3 in on top every spring.
Mulch piled against bark holds moisture there, and constant damp rots the bark and invites disease and rodents. Keep a 3 to 6 in gap of bare soil around the trunk. The mulch ring should look like a doughnut, not a volcano.