Mulch Ado About Mulch

Plus, 13 easy, eco-friendly ways to dispose of yard waste

Land art and photo by Nikola Faller of Croatia

Dear Heather, I am interested in affordable, natural looking mulch for my growing native garden. Do you have any recommendations and illustrative examples? — Rebecca, Florida

Slowly I turned, step by step . . . . If you don’t know the old vaudeville routine, that means MULCH MAKES ME APOPLECTIC! (You can watch Lucille Ball’s rendition below.)

My neighborhood is littered with pathetic plants stranded in seas of bark mulch. And “specimen trees” marooned in volcanic islands of mulch. How has the yard care industry bamboozled people into thinking bare mulch is a good look?

The “invention” of bark and sawdust mulch was beneficial to both the landscape and timber industries. Prior to this time, the timber industry used these lumber leftovers as hog fuel. Recycling these materials in a more environmentally friendly way theoretically benefits everyone. There are, however, some problems associated with bark and sawdust mulches that must be recognized by the landscape industry and homeowners. First of all, bark does not function like wood chips in its water holding capacity. Bark is the outer covering of the tree and is heavily suberized to prevent water loss. Suberin is a waxy substance that will repel water, and in fact helps explain why fresh bark mulch always seems dry. . . . Secondly, bark mulch is often a source of weed infestation. While newer mills have cleaner areas to hold surfaced logs, others still hold logs in weedy areas rife with horsetail and other serious landscape pests. — The Myth of Pretty Mulch, Washington State University

The best mulch is more plants. In healthy plantings, the plants you want crowd out the ones you don’t — aka weeds. That’s why I’m seeding my new beds with native annuals, as well as perennials. Annuals will mature in one season and cover the soil, while the native perennials establish themselves over several seasons.

Covering bare soil around young plants with dead organic material from your yard — the second best mulch — can also help during this establishment phase. One to four inches of leaves, wood chips, grass clippings, and even dead weeds (before they go to seed) adds nutrients, helps retain water, prevents erosion, and shades weed seeds so they don’t sprout.

I’m going to expand on how to use yard waste below. However, if you don’t have enough yard waste to mulch your new plantings, then good options include wood chips for woody plants and straw or buckwheat hulls for other areas.

Merry mulching!

— Heather

Why, How, Wow!

The Why and How of Using Yard Waste

Happy fall! In many parts of the country, autumn means falling leaves, presenting a quandary about what to do with them. Such “yard waste” can be an ecological boon or an environmental disaster, depending what you do with it. Here are the latest, research-based best practices for various types of yard waste.

Lawn clippings

Please, DON’T put lawn clippings in the trash. Lawn waste in landfill generates methane, which traps head in the atmosphere roughly 30x more effectively than the carbon dioxide produced when those leaves decompose in your yard.

If you can’t use your clippings on your property, leave them in paper lawn waste bags for town pickup. Most towns compost such waste.

Even better than town composting — which requires labor and fuel for transportation — is using lawn clippings in place of fertilizer or mulch in your own yard. Here are three great ways:

1. Mulch mow grass. The easiest, ecological way to dispose of lawn clippings is to use a mulching mower — preferably a battery-powered one — to chop them up and leave them on the lawn. The clippings will provide organic material to the soil, eventually breaking down into its component parts and fertilizing the lawn. 

2. Use grass clippings as mulch elsewhere. As long as it hasn’t gone to seed, lawn clippings can also be used as mulch elsewhere in the garden. For example, Pete and I pile grass clippings and other garden waste six inches deep or more to kill invasives in a corner of our garden.

3. Compost grass clippings. If you have a vegetable garden, home composting allows you to return nutrient-rich organic material to replace what you’re harvesting.

Of course, replacing lawn with native plants that don’t require mowing is even more ecological. The inefficient motors of gas-powered lawn equipment account for 5 percent of all air pollution, according to the EPA. In addition, traditional turf is made up of exotic (non-native) grasses that don’t support beneficial insects or other wildlife.

Dead trees

DON’T cut down a dead tree and remove its roots with a backhoe. Removing stumps wastes money and ecological potential. Unfortunately, there’s a lot of hogwash on the internet about the dangers of stumps, usually promulgated by companies looking for stump removal business.

Yes, rotting stumps and roots host fungi and insects, but that’s a huge benefit rather than a danger to your family or your garden. Dead trees, including their stumps and roots, provide vital habitat for more than 1,000 species of wildlife nationwide, according to the National Wildlife Foundation. 

At least 85 species of birds in North America are cavity-nesters, and dead trees — often referred to as ‘wildlife trees’ — sustain countless other organisms. As bacteria and fungi move in to hasten the decay of snags, stumps, and fallen logs, beetles tunnel through the softening wood to lay their eggs, followed by wood-nesting native bees. Nature’s homebuilders, the woodpeckers, show up to eat the insects and nest. In the ensuing years their handiwork creates condos for swallows, squirrels, and owls. — The Humane Gardener

So DO . . .

4. Make a safe snag. You or an arborist can remove any hazardous branches from a dead tree. The National Wildlife Foundation recommends leaving three snags (dead trees) per acre. And the nutrients from their decomposition nourish plants. Here in the northeast, our snag is a magnet for pileated woodpeckers.

5. Use a dead tree’s logs or chips. If you can’t make a safe snag, then you or an arborist can cut the tree into logs or chips. Use logs to make a log fence or line a path, where salamanders and toads can hide. Use chips in a thin layer as mulch around trees and shrubs or more thickly as a path surface.

Fallen or pruned branches

DON’T put fallen or pruned branches in the trash. Like lawn clippings, they will generate methane when they decompose anaerobically in landfill. Bundling them for town compost is a better option, but you’ll lose the benefit of their decomposition — yes, benefit — in your garden.

DO…

6. Leave branches where they fall. Letting branches decompose where they fall is both easy and ecological.

7. Leave branches around your garden. If you don’t like how they look where they fall, you can move branches to line a path or chop them into lengths to put in a log wall. Either way, they will provide habitat for cavity nesting bees and other wildlife.

8. Put fallen branches in a brush pile. Brush piles, which provide habitat for birds and other larger critters, are an important part of any ecological landscape.

Leaves under trees

DON’T shred, burn, or even compost leaves. And certainly don’t put them in the trash to produce methane in landfill. Many beneficial insects — notably, moth and butterfly larvae — overwinter in leaf litter.

Many organic gardeners opt for shredding their fall leaves for use in compost piles. While this is certainly a more environmentally friendly practice than bagging leaves and sending them to the landfill, shredded leaves will not provide the same cover as leaving them whole, and you may be destroying eggs, caterpillars, and chrysalis along with the leaves. — Xerces Society

Research has shown that moth and butterfly caterpillars are vital for transferring the sun’s energy to birds and other animals. Birds can survive without bird feeders, but most terrestrial species cannot survive without feeding their young hundreds of caterpillars a day. And moths and butterfly populations are declining rapidly. So please, create what entomologist Doug Tallamy calls “caterpillar pupation sites” on your property.

While monarch migration is a well-known phenomenon, it’s not the norm when it comes to butterflies. In fact, the vast majority of butterflies and moths overwinter in the landscape as an egg, caterpillar, chrysalis, or adult. In all but the warmest climates, these butterflies use leaf litter for winter cover. Great spangled fritillary and wooly bear caterpillars tuck themselves into a pile of leaves for protection from cold weather and predators. Red-banded hairstreaks lay their eggs on fallen oak leaves, which become the first food of the caterpillars when they emerge. Luna moths and swallowtail butterflies disguise their cocoons and chrysalises as dried leaves, blending in with the “real” leaves. — Xerces Society

9. Leave fallen leaves as mulch. Leaving up to four inches of leaves on your garden beds adds organic material effortlessly. Note: Evergreen leaves, like pine straw and live oak leaves, are best used when you want to inhibit growth; they often take longer to break down than deciduous leaves and can inhibit desired spreading by seed or stolon. Four inches of pine straw or live oak leaves, replenished annually, makes an excellent path.

10. Pile leaves to create a planting bed. Piling leaves six to eight inches over lawn is a great way to start a bed under a tree the following spring. The leaves will smother the grass (and weeds) beneath. Replacing grass with a bed of native perennials creates pupation sites for moths and butterflies.

11. Remove fallen leaves whole and use elsewhere. If you can’t use all your leaves where they fall, rake or vacuum them and use them whole elsewhere. Just don’t chop them up or compost them. The high heat of a compost pile will kill the beneficial insects nestled among them.

Sprinkling of leaves

By now you realize that mulch-mowing leaves — as opposed to grass — chops up all those pupating moths and butterflies. Ick. You also DON’T want to blow them into the street where the butterfly larvae nestled in them will be crushed by cars. The easiest, most ecological alternative is to . . .

12. Leave a sprinkling of leaves on grass. If your lawn is up to 20 percent covered by leaves, just leave them. They will blow around and break down without smothering your grass.

Flower stalks and seed heads

Remember the old rules about “cleaning” your beds in the fall? That’s important for vegetable gardens, but not for the ornamental plants in your yard. In fact, ecological yard care often means forgetting the old horticultural rules that misapplied agricultural practices to ornamental gardens. So, DON’T cut down perennial stalks and seed heads in the fall.

13. DO leave stalks and seed heads. About a third of our 4,000 native bee species nest and overwinter in the pithy stems of meadow plants like goldenrod. And birds like juncos and goldfinches live on the seeds of native flowers as they move south and over the winter. Fortunately, stalks and seed heads give gardens beautiful winter interest, as naturalistic garden designers like Piet Oudolf have helped us see. (Using some seed heads to propagate more plants won't hurt.)

If tall stalks bother your sense of order in the spring, you can cut them to two feet without eliminating much bee nesting area. Entomologist Heather Holm found that where most bees overwinter in the first 18 to 24 inches of plant stalks; if you leave two feet of stalk, the bees will nest there the following year.

If you have a meadow and area where woody plants will take over without occasional cutting, consider mowing a third of the meadow each year and leaving two thirds for the birds and the bees.

Wow!

Land art and photo by Nikola Faller of Croatia

Related Resources

• Want to learn more about insects and yard waste? See Xerces Society’s Leave the Leaves.

• Want to learn more about designing a winter garden? Read this Q&A with Piet Oudolf [gift link] or check out my article Plants that Look Great in Winter.

• Want to seed a meadow this winter? Read Seed a Meadow Now for Big Savings and start planning now.