Cover your ground, for your plants' sake
Nature abhors bare ground, and so should you. Her response to naked earth is to clothe it, a job at which many weeds excel.
Bare soil is too easily blown and washed away by wind and water. Rainfall pounding on it seals pores, making it much harder for water to penetrate. This further contributes to erosion, which snowballs as moving water increases speed and carves out rivulets and then gullies. Bare soil is also thrashed by sunlight, which creates a hot, dry root environment in summer. In winter, cold penetrates deepest in bare soil.
Those weeds that naturally protect bare soil have some obvious drawbacks in the garden. So one way to keep garden soil protected and free of weeds in the coming months is to keep it covered with something else: mulch. Consider laying mulch over any bare ground.
Mulching does more than just keeps weeds at bay and soil protected from the elements. On garden paths, a surface covering diffuses pressure from footsteps, wheelbarrow wheels and tractor tires. Plants aren't growing in paths, but rainfall still must penetrate the soil there, and some roots of plants bordering paths find their way there.
MULTIPLE BENEFITS FROM ORGANIC MATERIALS
Except for stones, bricks and other inorganic materials that are sometimes used as mulches in paths and rarely if ever need replenishing, the best materials for mulching everywhere in the garden are organic. These materials — compost, straw, pine needles, leaves, wood chips and the like — need regular renewal because, with time, they decompose. ("Organic materials" are materials that were once living.)
Don't begrudge organic materials for disappearing, though. As they do, they enrich the ground with soil-building humus, release nutrients into the soil, and nourish beneficial soil microorganisms. When we lay these materials on top of the ground rather than digging them in, they can protect the surface, and their goodness gradually seeps downward for long-lasting benefits.
How frequently mulch needs to be replenished depends on how quickly it decomposes, and that in turn depends on the material and the weather. Hotter and moister weather speeds decomposition along.
Generally, I dress my whole garden with mulch an inch or so deep in the autumn because that's when certain materials such as leaves are available. The materials, then, have all winter to begin melding with the underlying layer of soil — and I'm left with less to do during the flurry of spring gardening activities.
WHAT TO USE
My trees, shrubs and informal flower beds get a blanket of autumn leaves (either fresh or allowed to decompose for a year or two) or wood chips. But any organic material that carries along few weed seeds is good. Trees, shrubs and flower plants aren't generally heavy feeders; besides protecting the soil, any of these mulches generally also provides sufficient nutrients for these plants.
The vegetable garden goes into winter with a fresh dressing of wood chips on the paths and, except where garden plants are still growing, an icing of rich, brown compost on each bed. Vegetable plants are hungry for nutrients, and compost is particularly rich in plant nutrients.
A few flowering plants are hungrier for food than most others. So roses, delphiniums, chrysanthemums, daylilies, hydrangeas and tall phlox would also like that mulch of compost that the vegetables get.
At the very least, the time to replenish any mulch — whether it is wood chips, compost, straw or another organic material — is as soon as bare soil begins to peek through.