by Susan Harris
Are your beds and borders mulched and ready for winter? Mulches do a lot to moderate soil temperature, which means preventing freeze-thaw cycles that can cause plants to heave out of the ground and their roots to freeze. That’s just one of soooo many reasons to mulch and why low-maintenance, eco-savvy gardeners swear by the stuff.
More Reasons to Mulch
- To suppress weeds
- To retain moisture and conserve water.
- To prevent erosion
- To reduce compaction of soil by cushioning the impact of downpours
- To prevent mud splatter on plant and hard surfaces, like your house
- To add nutrients to soil AND improve the soil’s structure, which means it can hold more water and better use soil nutrients from any source
- To increase the populations of earthworm and beneficial soil microbes
- To make your garden look well kept and amenable to planting — like a garden
When and How
- At least yearly, apply or top off to replenish what has decomposed. Many gardeners in colder climates do their heavy mulching in the fall, but it can be applied any time of the year.
- Also, apply mulch immediately after disturbing the soil, especially for planting something.
- AND to cover bare ground at any time.
- Remove weeds.
- Loosen top of soil (a tool called the cultivator does this job very quickly), incorporating what’s left of the old mulch into the soil as you do it.
- Apply 2-8 inches of mulch, depending on the type of soil you have (sandy soil needs more, clay soil less) and which mulch you’re using – details below.
- Never mulch on top of plants or have mulch touching their stems and most important of all, don’t pile it up against tree trunks. (The result is called a mulch volcano and it’s horrible for tree health!) So keep mulch at least 2 inches from all plants.
- And avoid putting mulch against your house, unless you’re trying to attract termites.
Great Organic Mulches
(For walkways or driveways, inorganic mulches like gravel and recycled tires are fine, but around plants, only organic mulches provide nutrients and improve soil structure.)
Leafmold is simply chopped and aged leaves. Though it’s rarely sold, it’s pretty easy to make and many local governments provide it for free or very cheaply. These partially decomposed leaves are nutrient-rich and excellent as mulch or a soil amendment. Apply 2 to 3 inches.
Whole leaves may or may not make a good mulch in in your borders, depending on their size, thickness, and how many there are of them. Oak leaves, for example, are large and don’t decompose over winter, so there they are in the spring having to be removed, They can also smother groundcovers, and form dense mats that keep rainwater from penetrating the soil. You just may not want to see dead leaves in your borders and blowing around the garden, and find the mulched look more to your liking. But chopped or shredded, dead leaves make a darn good mulch. It’s as easy as mowing over them with a grasscatcher, then dumping where you need the mulch. Apply 2 to 3 inches.
Bark mulches are slow to break down, so last a long time, and are good-looking. Redwood is especially attractive but more expensive, and not the best at retaining water. Cedar bark can crust, preventing water penetration. So pine or “hardwood” bark is best. Fresh bark can be toxic to young plants, so age first, or buy bark that shows some of the discoloration of age. And speaking of store-bought, some brands are mixed with large amounts of shredded wood, which bleaches white, so look for an even, dark color. It comes in nuggets and mini-nuggets, or shredded, with the shredded version preferred by many gardeners who’ve seen their nuggets wash away during hard rains. The bark used is a waste product from lumber companies. Apply 3 to 4 inches.
Wood chips or shavings from local arborists make an attractive mulch that breaks down very slowly, and is moderately priced or free from municipalities and tree companies. Still, because of reports that they deplete the soil of nitrogen, many experts recommend them only for paths or play areas, or compost them for a month or two first. Others simply add a source of nitrogen to compensate for the wood chips. Apply 3 to 4 inches.
Pine Fines are fine-textured pieces of pine bark, aged and screened, and water penetrates them easily. Apply a thicker layer than for other mulches – 4 to 6 inches. It looks great as a mulch but is also outstanding mixed into the soil as an amendment. Best used with acid-loving plants because it lowers soil pH. Apply 4 to 6 inches.
Straw is a good mulch but make sure it’s really straw and not hay, which is full of weeds. Apply it even thicker – 6 to 8 inches – in your vegetable bed. It’s just not ornamental enough for perennial and shrub borders – let’s be honest.
Compost is plant or animal waste that’s completely decomposed and now looks something like coffee grounds — black gold. It’s a great source of nutrients it is, and a boon to soil structure. Spreading an inch of compost on beds and borders every year gives the soil and plants everything they need. Compost is also the best possible soil amendment for preparing a bed or at planting. Maryland’s own Leafgro is an excellent product.