Right mulch, right place

Walk into any garden center and you'll see all kinds of mulches lying in bins or on pallets. With so many choices, it's sometimes tough to figure out the right one for your situation. Is gravel better than pine needles? What about cypress mulch? And are those free mulches such as leaves just as good?Mulches are designed to keep the soil warmer in winter and cooler in summer, to stop the ground from losing water and to control weeds. But no mulch is perfect. Each has its own strengths and weaknesses that make it more appropriate for certain situations, less in others.

Here's a short list of popular mulches and recommendations about where they might work best.

Grass clippings make good mulch for gardens, and even around trees and shrubs, but they break down quickly. Once the clippings have broken down, they'll help revitalize your soil, but they'll no longer be effective at controlling weeds. If you use grass clippings as mulch, about the best you can hope for is one season of weed control. That makes them perfect for a vegetable garden, as long as the clippings are not from grass that's been treated with a herbicide in the previous nine months.

Leaves

Dried leaves make a very effective mulch in gardens and are OK around trees and shrubs, though not ideal. They don't break down into organic matter as quickly as grass clippings do, so they typically provide a weed barrier for a full year, but they have a tendency to blow away.

If you use leaves as mulch, make sure that none come from black walnut trees. Those could poison nearby plants, especially tomatoes, peppers and eggplant.

This mulch comes from harvesting pine trees for wood and paper. Because it breaks down very slowly, sometimes over two years or more, it's more appropriate for shrubs and trees than for gardens.

Because it, like pine bark, decomposes very slowly, cypress mulch works well around trees and shrubs. However, some green gardeners recommend against using it because harvesting the trees depletes the cypress swamps, which are not a quickly renewable resource.

This is a serviceable mulch, but unlike all of the organic mulches above, it doesn't break down and feed the soil. Gravel also can collect heat and burn the stems of young trees, shrubs or perennials by reflecting sunlight. In addition, gravel and rocks aren't as effective at controlling weeds in the long term. Soil builds up between the gravel, and weed seeds will find their way in and grow. The only places where gravel mulch really makes sense? Underneath a deck or beside a house where you're not planning on growing plants.

Landscape fabrics are used around houses to provide a weed barrier. They work, but anything that you plant in this fabric will be at a disadvantage because the fabric blocks water from getting into the soil.

Mulch is usually best applied a week or two after planting trees, shrubs and perennials and annuals that are being planted from plugs. If you're planting seeds directly into the soil, wait until these plants are 4 to 6 inches above the surface of the soil before putting mulch down.

Most mulches should be applied to a depth of about 2 inches in the garden, a little deeper around trees and shrubs. Never pile up mulch around the stem of a plant.