Mulch was nature’s idea long before it became man’s. Fallen leaves, pine needles, rotting wood and vegetation, decaying flowers, ripe fruit, rocks rising to the Earth’s surface—the environment naturally produces and disperses “mulch,” adding a protective coating to the ground.
Knowing the various types of mulch and understanding how best to use them will enable you to assist Mother Nature and easily beautify your lawn and garden.
Why Should You Mulch?
Mulching your soil might just be the most important thing you can do for your property—not only for the earth itself, but also for anything growing there. When used properly, mulch offers a multitude of benefits to homeowners. All mulches will reduce soil moisture evaporation, regulate soil temperature and discourage weeds. Depending on the type, some mulches may do even more.
- Mulch helps prevent moisture loss. No matter what kind of mulch is selected, mulched soil will retain about twice as much moisture as bare soil. Not only will it need to be watered less, but when it is watered it will remain damp longer.
- Mulch keeps soil cool in hot weather and warm in cold weather (by as much as 13 degrees according to Cornell University’s Horticulture Diagnostic Laboratory). This helps protect plant life, especially in places with extreme temperatures.
- Mulch reduces weed growth, provided that the material used is free of weeds and seeds, and that the mulch is deep enough to smother any germinating or budding weeds.
- Mulch fights topsoil degradation. When water droplets hit the ground, the impact causes small particles to erupt and scatter. This leads to soil crusting—which impedes water absorption—and soil erosion.
- Mulch helps prevent soil-borne diseases. The same soil splashing that causes crusting and erosion also can expose plants to contaminants in the soil.
- Mulch combats soil compaction. This encourages root growth, increases the soil’s oxygen content, and helps water movement. Mulched plants actually grow more (not just deeper) roots.
- Organic mulches can improve soil structure. As the mulch decays, it turns into topsoil and adds nutrients to enrich the dirt.
- Mulch protects trees and shrubs from potential damage caused by lawn equipment.
- Mulches beautify the property, adding color and texture.
Many Types of Mulch
Mulches fall into two general categories: organic—meaning made from living, or once living, material—and inorganic. What’s the difference for your lawn? For one thing, any organic mulch will break down and enrich the soil in the process. Inorganic mulches, on the other hand, will last much longer. You don’t have to spend more time and money to replace it.
To determine which mulch is best for you, take into consideration each kind’s characteristics, what you hope to accomplish and where you plan to use it.
On top of enriching the soil, organic mulch has another point in its favor: It attracts and harbors some beneficial organisms. Ground spiders, worms and ants, among others, nest in the material and prey on the larvae and eggs of other insects contained in the ground below.
Some organic mulch options (but certainly not all) include:
- Pine Bark: A popular mulching choice, pine bark comes in nuggets, chips or shredded form. Finer-textured materials need replacing sooner, but also add nutrients quicker. Acid-loving flowers like azaleas, rhododendrons, camellias and gardenias benefit from pine’s acidity. However, some insects, including termites, are attracted to pine, so avoid it in places where they are a concern.
- Hardwood: Consider hardwood mulch as an alternative to pine bark—especially around roses. Choose from either wood chips or shredded hardwood forms. As with pine bark, though, termites view hardwood as a gourmet feast. Select another mulch in areas where they are a problem.
- Pine Needles: As with pine bark mulch, pine needles lend a slight acidity to the soil. Even better if you can simply rake up your own needles and use them, to save money.
- Sawdust: Sawdust also lends acidity to the soil. Watch for compaction and reapply every spring.
- Straw: Forget hay as mulch: It’s often full of seeds and weeds. Straw, on the other hand, is cheap and easy to find. However, it attracts rodents, can be unattractive and needs replenishing yearly. Try using straw to cover freshly seeded lawns, to mulch a vegetable garden or strawberry patch, or to winterize shrubs.
- Leaves or Grass: For another “homemade” mulch, try mown grass. Let the grass dry slightly, to prevent matting, before building the mulch up to about 2 inches in depth. Better yet, shred leaves coarsely (you can mow them to accomplish this) and spread in a layer of 2 to 3 inches. As the leaves decompose, simply add more to refresh your mulch. (Allowing the leaves to partially decompose before using them—creating something called “leaf mold”—makes for an even richer mulch that adds nitrogen, humus and other nutrients to the soil.)
Looking for something organic that’s not described in these choices? Check local home improvement stores and area manufacturers. Depending on what grows in your area, you may have other choices such as cocoa bean hulls, pecan shells, buckwheat or cottonseed. Even try perennial ground covers like ivy, mondo grass, periwinkle or pachysandra. Though not technically mulches, these plants still function as one.
While inorganic mulch products won’t add nutrients to the soil, they will still fight erosion, retain ground moisture, moderate soil temperature and deliver other essential mulching features. They also have one big advantage over organic mulches: They’re permanent. Some more popular choices include:
- Rocks: Perhaps the most widely used inorganic mulch, rocks come in three sizes: pebbles, gravel and stone. Use rocks in permanent areas where you don’t intend to replant. Plan to use about an inch to control weeds. Avoid spreading limestone around acid-loving plants, as limestone raises the pH in the soil.
- Ground rubber from tires: The new kid on the block, so to speak, ground rubber is a great way to recycle old tires and produce a useful mulch. In addition to coming in black (which can build up heat and possibly affect plants), rubber mulch is sometimes dyed fun colors like red, yellow and blue. Rubber is also a kid-friendly product.
- Black plastic sheeting: If function matters much more than beauty in the area you plan to mulch, consider using black polyethylene sheeting, or black plastic. It’s perfect for preventing weeds and retaining moisture. The drawback is that it won’t let new moisture reach the ground, either. Cutting holes in the plastic, or buying plastic sheeting specially formulated for lawn and garden use featuring pre-made holes, solves this. Use sheeting to cover vegetable seeds (allowing you to plant sooner) or cover them with a layer of chips, stone or other mulch to create a hidden weed barrier. For a cheaper (and perhaps shorter-lived) option, use black plastic garbage bags. Avoid clear plastic, which lets sunlight in to nourish the weeds.
- Landscape cloth: Another option, though also unattractive, landscape cloth functions much like black plastic. Spread a layer of chips, stone, or other mulching material over the cloth to improve the appearance. The biggest advantage of using landscape cloth instead of plastic is that it allows air and moisture to pass through.
More Marvelous Mulching Tips
In addition to organic or inorganic, mulches may be labeled as summer or winter. So-called winter mulches (such as straw, leaves and pine needles) are often spread in late fall to insulate woody plants for the winter. Wait until the soil has cooled, but isn’t yet frozen, for best results. Summer mulches, on the other hand, get applied in springtime once the soil starts to warm. Spreading mulch too soon can actually hold the cold in the soil.
When working with new plants, trees or shrubs, spread the mulch as soon as you have them in the ground for best results.
Grade your soil, if necessary, before spreading mulch. Not only will water pool in low spots (causing organic mulches there to decay quicker), but when applying mulch, the natural tendency is to level it out. If the ground isn’t graded first, this can result in thicker and thinner areas, which lessens the mulch’s effectiveness.
Weed before mulching, even apply a pre-emergent herbicide, if desired. Keep mulch a couple of inches away from wood stems and trunks to prevent rot. Work old mulch into the soil before spreading new material, to enrich the soil further.
How much mulch should you use? In general, the larger the pieces, the deeper the mulch should be. A couple of inches of fine pebbles or shredded bark, for instance, is comparable to 3 or 4 inches of limestone or wood pellets.
For more information on mulch, and how to determine the amount of mulch you need, see Clemson University’s guide on the Savvy Gardener.