NOT SURPRISINGLY, THE MEDICINE wheel garden’s showy top layers of colorful flowers, berries, and bright foliage consume most of our attention; hen we say “garden,” we think of the plant parts that we can see. To sustain the vitality of these visible layers of growth, however, the more mysterious underground plant layers require careful nurturing. The root zone is a labyrinth of essential nutrients and movement that enable the whole plant to thrive and look its best. Mulching can favor all layers, from bottom to top.
Covering the earth, even lightly, prevents the soil around sensitive roots from drying out too rapidly. By conserving moisture, mulching eliminates the need for frequent watering, which is impractical in many regions—and wherever you live, saving water is desirable and important. If your garden rests on a slope, mulching will help to check erosion by water runoff and wind. Some mulches also provide valuable soil nutrients.
Top-dressing the garden soil around the plants is a perennial activity for many gardeners. Mulches protect and preserve your plants and also enhance the attractiveness of the plants and garden layout. Yet another part of their duty is to keep the undersides
of the plants clean during rain and watering. When selecting mulch, consider your garden’s special needs: the type of soil, the lay of the land, and the plants you have chosen. The design and style of your garden may dictate use of certain mulches.
Mulches can be divided into organic and inorganic types. Organic mulches, such as aged compost and leaf mold, serve as temporary soil covering and enrich the plants and earth as they decompose through the seasons. Inorganic mulches are more permanent, especially if properly installed. For example, a cover of river cobbles over a layer of landscape fabric can last for decades and requires little maintenance beyond removing dead leaves and plant clippings as needed.
Rapidly decomposing mulches, such as compost, leaf mold, straw, and hay, are very valuable for all soil types. If your soil is light and sandy, mulches such as these, especially compost, will enrich it and add moisture retention qualities. If your soil is heavy with clay, organic mulch can help to lighten and loosen its texture over time. Even if your soil is just perfect—loose and dark with humus—mulch will add nourishment and protect it from rapid drying.
Compost is a universal, increasingly valuable soil enricher. The health and vigor of many gardens can be improved by top-dressing with good compost each spring. Compost begins with garden waste and food scraps that can range from discarded vegetable and fruit parts to eggshells, coffee grounds, and tea leaves layered with grass clippings, leaves, and straw or hay. Over time, these materials break down and become humus. This can be created quite rapidly in compost bins, where the mixture should be turned over often. You can also create large compost piles or bins that are not turned and slowly decompose. You can dig the rich humus from underneath, at the side of the pile.
Many gardeners in our eastern states, including those managing public gardens and large estates, chop and recycle autumn leaves and choose leaf mold mulch as their free, sustainable preference for building good soil. Like compost, leaf mulch breaks down quickly and needs to be replaced each year. Some mixtures of leaves tend to be acidic. If a test shows a change in the soil pH, a dusting of lime or broken eggshells and chopped yarrow scratched into the leaf mold and soil will help.
Two other good seasonal mulches, straw and hay, both decompose rapidly and can be turned into the soil and replenished. Straw mulch, which consists of the stem bottoms from the wheat harvest, is best kept loose and spread several inches thick around the garden. It is an excellent soil enricher but should be used with caution around food and medicinal plants, because wheat fields are treated with herbicides. With hay mulch, if possible choose young green hay or salt hay, as mature hay is full of seeds and can introduce vigorous weeds into the garden.
A number of organic mulches derive from tree bark or wood. Some of these have an appealing decorative quality as well as protecting the soil. Red cedar, Juniperus communis, is a common “weed” tree in many states and can be easily culled from the ecosystem without harm to other organisms. Cedar bark mulch and red cedar shavings come mainly from residue of cedar furniture and fencing manufacture. The fragrant mulch of red bark will last throughout the season if the shavings are applied several inches thick over the ground. Cedar mulches are insect-resistant, so they can be laid close to the house or other buildings where insect pests might be a problem.
Pine bark mulch and pine nuggets come from plantations and natural stands of pine that have been clear-cut and debarked for paper or lumber. Both these mulches are good soil modifiers and will last several years if not used in pedestrian areas and if put down over landscape fabric, not directly over soil. Laid around permanent plantings, the pine nuggets are the more decorative of the two.
Attractively straw-colored and without obvious odor, cypress mulch is also long-lasting. After young cypress trees are ground and planed in furniture manufacture, the leftovers are shredded to make this mulch. (Old-growth cypress is not used.) Different textures of cypress mulch are available; the finer particles hold a slope better in washout areas, while the larger particle size lasts longer.
Nugget-sized bark renderings from trees such as oak and sycamore provide hardwood mulch. Unlike insect-repellent cedar mulches, this one could become a home for insects like carpenter ants or termites and should not be placed too near the house. It is great beneath shrubs, trees, and tall herbs, especially in woodland gardens. In some settings, this mulch may last a couple of years before needing replacement. Usually a coarsely shredded, random mix of shrub and tree materials, wood chip mulch from landscape and clearing projects is often widely available. While useful for footpaths and many garden areas if applied several inches thick, it can leach vital nitrogen from the soil for the first year or two until it decomposes and returns the theft by enriching the area.
When environmental conditions are right, wood chip mulch may produce a range of fungi after rain—an extra benefit. Fungi are the ultimate decomposers.
Cocoa bean hull mulch is a renewable resource that when fresh has a wonderful fragrance and rich brown color. The small size and uniformity of the hulls make it visually appealing. A good conditioner for clayey and sandy soils, it lasts only about one season, as it biodegrades into the soil, and it should be replaced each spring.
Cottonseed hull mulch comes from the cottonseed residue after cotton and oil are removed. Composted cotton burrs are the prickly husks from the outer cotton boll. Both these mulches are shortlived but excellent soil conditioners. They work best when applied two to three inches deep and kept fairly moist. Caution: Because cotton is an intensively treated crop, composting may not remove enough of the residual chemicals for safe use of the burrs with food and medicinal plants.
These extremely elegant mulches are often used for Japanese and xeriscape gardens, especially in the desert Southwest, southern California, and Florida. Along with stones of various kinds, this group includes mulches made from dead coral, seashells, and
beach glass. These permanent mulches are more expensive than others.
Stones smoothed by long contact with water have a particu- Similarly American Indian larly “finished” appearance for use as mulches. Water-smoothed traditionalists perceive rocks stones selected for river rock mulch rank as one of the best perma- and stones as each having a nent mulches, especially when applied over a layer of landscape spirit that can tell us certain fabric. This mulch is most suitable for applications around shrubs things. or trees, in meditation gardens, and for footpaths. Beach stone mulch is beautiful, but large-scale removal of choice beach stones has damaged many picturesque beaches. Removing stones from some beaches is now forbidden. Other stony waterfronts willingly give their cargo for landscape use, but the stones must be washed repeatedly to remove the salt. For use on garden paths, the salt residue is no problem, as it suppresses weed growth.
In contrast to stones shaped by water, lava rock mulch is porous and rough-textured. Produced by volcanic activity, lava rock is perceived by some American Indians as coming from the heart of the Earth and the passion of creation. Mined from surface pits in western states, it is used primarily for road building and garden adornment in the Southwest. This mulch is tough on hands and plant stems and it traps falling leaves and plant debris, but if you clean the surface carefully, it will maintain a carpet of permanent, interesting textures.
Despite its name, white marble rock mulch is not actually marble or even stone, but gypsum (calcium sulfate), a chalky mineral mined from surface pits. This mulch is excellent to delineate footpaths and walkways in the garden and to spread between large flagstones and fieldstones. It is most attractive in deeply shaded areas and on bright moonlit nights year-round. Ideally, white rock mulch should be put down over a sheet of landscape fabric, yet it
eventually may look dingy as it acquires mineral salts from its surroundings. It also traps falling leaves and other plant materials and should be cleaned by hand each season or, in some locations, top-dressed with additional thin layers of white rock once a year.
While collecting beach stones is widely discouraged, sea coral and seashells for mulch, salty gifts from the sea along storm coasts, can be collected freely in most areas. These mulches look beautiful in coastal gardens, especially on bright moonlit nights when they catch the moon’s glow and reflect it back. They also provide a somewhat musical crunching noise beneath the feet. Chipped shells from shellfish farms or your last great oyster and clam bash can be artfully used in narrow beds around the house and on footpaths, providing wonderful walkways through the garden. These arrangements recall historical uses in Nantucket, Martha’s Vineyard, Cape Cod, and coastal Maine. Wash and rinse these mulches thoroughly before putting them down. Gardeners want the lime they contain but not their salty qualities, unless used for pathways.
Beach glass mulch is a colorful, renewable resource for small paths and decorative garden areas. This mulch is best applied over a cover of landscape fabric for cleaner, long-lasting permanence. The small, smooth pieces of glass also look beautiful spread around potted plants. In states where glass bottles are not recycled, you can toss bottles into a small cement mixer with several shovelfuls of sand and small stones and tumble them for a few hours to make your own multicolored “beach glass”—the ultimate in recycling.
When making your choice of mulches, there is no need to restrict yourself to only one type. Our big, public medicine wheel garden at the Institute of American Indian Studies sits on a steep woodland slope. During the fall and winter, we top-dress the garden with leaf mulch and compost, digging it in around the big perennial plants. Each spring we apply fresh red cedar mulch to the four main quarters of the garden. This colorful mulch is easily put down and spread around colonies of perennial herbs. We spread it about one inch thick so that new plants can emerge without being smothered.
The four main pathways into the center of the garden are top-dressed with white rock mulch, which is also renewed each spring. This combination of mulches produces a vivid white cross surrounded by deep red and rimmed with large white quartz and marble boulders.
Oriented to the four cardinal directions, the early spring garden looks like a sacred jewel on the landscape. Later on, the profusion of blossoms and leaves almost masks the garden’s artistic layout, and by late summer, the medicine wheel garden looks like an herbal classroom filled with healthy plants and winged pollinators. The garden remains a cathedral for hummingbirds, butterflies, and butterfly moths until the first frost, when, as we cut back the mature growth and dress the garden for the winter, the medicine wheel pattern emerges again.
