Winter time freezes and snows can cause damage to your hardy plants when young or if the low temperatures exceed winter norms and you didn't prepare your garden carefully. Also, winter can cause problems with water runoff from heavier rains or from melting snows. Although plants are the least expensive part of a garden (the most being creating structure), after you've cared for a plant and selected it for your garden, you hate to see it die.
Winterize Your Garden with Mulch
Follow your last weeding of the fall by covering all your garden beds with a good layer of mulch, 3-6 inches deep using mushroom compost or recycled yard waste compost. If you keep your garden beds covered with ground cloth and cedar chips, bark, or bark dust, be sure to check your beds and see that the ground cloth isn't exposed. The bad part about wood products used on your garden is that they leach nitrogen as does rainfall and snowfall, whereas mushroom compost, recycled yard waste compost, steer manure and chicken manure help fertilize your plants and enrich the soil when you turn your garden beds in the spring. I like steer manure and chicken manure on top of my evergreen, perennial and bulb gardens. Roses and herbs in the mild Puget Sound area can be encouraged to bloom and leaf out to soon if you provide fertilizer in the mulch.
Newly planted shrubs, roses, perennials and trees need extra care. Three plants especially appreciate a 6-12 inch layer of leaves or straw stacked around their baselavender, roses and rosemary. Be sure that in doing this, you leave some leaves exposed to the sunlight.
Winterize Your Garden by Pruning
Pruning branches of your roses, trees and evergreens can prevent unattractive breakage. I often leave my rose branches fairly long because it's easier to prune off dead parts after winter and because we aren't much affected by wind.
Winterize Your Garden by Taking Tender Plants Indoors
Know your areas planting zone and its extremes of high and low temperatures. Any plant that isn't tolerant of your area's low temperatures should be brought inside during winter. Examples for the Puget Sound area include geranium which will die back during a freeze and fuschia. Trim back the branches of these plants to the last leaf or two on main branches. Place somewhere dark and water occasionally with a small amount of water. Too much water will cause the plants to rot. In Spring, bring into sunlight indoors and feed a light fertilizer like 10-10-10. Bring inside any tender bulbs if you can plant them early enough in spring to allow them to bloom; a Northwest example is begonia bulbs.
Leaf Removal and Winterizing Your Garden
As soon as fall leaves fall, I rake and bag them up, then spend most of winter ridding our load of 40+ bags into our recycle barrel. Ridding your yard of leaves will prevent your lawn from dying, prevent seeds from sprouting into new trees in the case of maple and cottonwood, and minimizes the amount of mold in your air. The exception is my garden beds. Many times I let the leaves remain on the garden beds to add an additional layer of mulch.
Fertilizers and Winterizing Your Garden
The worst thing to happen to your plants is a late autumn leaf out and bloom followed by a deep snow or freeze. Save your fertilizer until early spring, although I will fertilizer evergreen shrubs like camellia, rhododendron, azalea, and viburnum in the late fall and in the early spring if there's enough fall rain to flush the fertilizer to the roots.
Winterize Your Garden Drainage
Drain spouts and downhill areas of your yard are subject to drainage problems that come with too much rain or the melting of snow. Where the downspouts drain into my garden beds, I often leave a furrow in the mulch so that I don't get sitting water. Make sure your gutters are cleaned out on the roof and that the opening at the base. We have catch basins that need to have the downhill muck removed.