May 25th, 2012
The Ten Commandments of Mulch
1. The word “mulch” does not mean wood chips or shredded bark. “Mulch” is anything that covers the soil to retain moisture and prevent weeds. Nurseries would LIKE you to think that wood = mulch because they’re often paid to take wood chips and shredded bark from tree cutters trying to avoid high landfill costs. If they can then sell it to you as mulch, they get paid twice.
2. There is no better mulch than compost. No, compost is not acidic and it doesn’t harm plants (it’s plant FOOD!). But nurseries have to actually buy compost, so some might tell a little…eh, ‘fib’ to achieve that higher profit. Did I just say, “fib”? I’m sorry—that’s not fair. I meant to say: “Liar, liar; pants on fire”. I apologize for the error. Anyway, in a groundbreaking study from Iowa and Ohio State Universities two inches of compost prevented weeds just as well as two inches of ground wood mulch. And the compost provided all the food it’s plants needed for the season, while the wood mulch actually increased the plants’ need for food (see #9, below). You gonna believe some guy what wants to sell you wood to make a bigger profit? Or the published results of University researchers?
3. Compost is pretty. When I spoke with that study’s lead researcher, Dr. Dan Herms, he observed that the compost mulch was as black and nice looking as the dyed black wood mulch they were testing it against. It looked so nice, in fact, that he switched to it personally. Simply put, a mulch of compost provides all the benefits you can get from mulch with none of the negatives of wood or other troublesome mulches. Other mulches of high regard include shredded Fall leaves, pine needles and pine straw; and really cool esoteric local ones like cocoa bean shells and rice hulls.
4. Wood mulch is not nice—especially dyed wood mulch. It’s made by grinding up old pallets and other trash wood, and may contain arsenic, creosote and other nasty stuff. It is the lowest quality mulch you can buy. Oh, except for…
5. Rubber mulch is WORSE! You know you have to pay to throw away your old tires. Do you really think it’s a smart idea to buy them back after somebody grinds them up and calls them mulch? Rubber mulch leaches zinc and other pollutants; and it STINKS in the summertime. Why does everyone with a toxic waste disposal problem always have to think, “Hey—I’ll bet we can convince people to use this stuff in their garden!”?
6. Thou should not use wood mulch near thy home. As many hundreds of listeners have told us they learned the hard way, any kind of wood mulch—like wood chips, so-called triple-premium shredded bark and those increasingly popular root mulches—can breed a nuisance mold known as ‘shotgun’ or ‘artillery’ fungus that will permanently stain homes and cars within 30 feet of the mulch with impossible to remove fungal spores that look like little tar balls. Sorry, but the reason University Bulletins don’t offer removal tips is that once they dry, those spores are there for good.
7. Thou should not run ANY mulch right up to thy home. Everyone in America has subterranean termites in their landscape. Subterraneans prefer to travel under cover. Mulching right up to the side of your home with anything—even stone—provides the protection and moisture they require to find their way RIGHT to your framing. Always leave at least a six-inch area clear around your home.
8. Never touch a plant with any mulch. Mulches are for preventing weeds and retaining soil moisture—they are not blankies; they do not keep plants warm or comfort them. Just the opposite, in fact: ANY mulch that’s piled up against a plant stem or tree trunk provides cover and traps moisture, inviting pests, disease and rot to destroy that poor plant. There is no good reason for mulch to ever touch a plant; there are many good reasons for it not to. Always leave a few inches wide open around the trunk or stem.
9. Wood mulches starve plants. As we have often warned, wood is high in carbon. Carbon seeks out nitrogen to help it break down into soil, just like in a compost pile. Mulch your plants with wood and the wood will steal their food in its quest to become really nice dirt a few years from then. When I hear that a plant isn’t thriving, my first response is generally, “get rid of the wood mulch”.
10. You CAN use wood mulch! It’s great for smothering unwanted plants and keeping weeds down in walkways far away from homes and cars.
For even more info, check out last year’s diatribe on this topic: