Mulching benefits your soil; it holds moisture and adds fresh organic matter, which improves soil drainage, texture, and fertility. It also prevents weeds from growing, since it deprives their seeds of the light they need to germinate.
Martha's favorite mulch is a local product called ''Sweet Peat''; it's made of composted stable bedding. To find a similar product, contact stables in your area and ask if they use wood shavings as bedding (you may have to compost it yourself). Your local garden center may also know of a source.
Some gardeners use composted leaves alone for mulch, but remember that the leaves need to be well decomposed, or they'll tend to blow around the garden and look unkempt. Martha prefers to mix them with other composted organic matter to create a more substantial mulch.
Coarse-textured mulches such as hardwood bark mixes work well under trees and in shrub borders. Use the finer grades such as chips or shredded bark, not the largest grade, which is unattractive and never breaks down into the soil.
You can buy the mulch in bags at a garden center, though if you need to cover a large area, you can have the garden center deliver several cubic yards in a truck. When it first arrives, the mountain of mulch may seem like a lot, but you'll find it disappears quickly once you start spreading it around.