If the weather suddenly turns cold, early-flowering and tender plants may need special protection to avoid damage by freezing temperatures. There are several ways you can provide winter protection, including 1) mulching; 2) covering the plants; 3) moving them; or 4) taking advantage of a light snow covering.
MULCHING: This is one of the best ways to protect plant roots. Bark, straw, sawdust, peat moss, leaves and even grass clippings are the most common mulching materials. Remove the weeds (if possible) before applying the mulch. As a rule the mulch should be about 2 inches in depth. However, there are exceptions that will be stated a little later in this information bulletin. Keep the mulch an inch or two away from the trunk or main stem of the trees and shrubs. Again, there are exceptions, such as roses and cane berries, where the mulch is actually mounded over the canes. Then when spring arrives, after all danger of frost has passed, these mulching materials are pulled away.
Occasionally check through the mulching material, (about once a month) to be sure that moisture is getting to the soil below. This is especially important for plants that are situated under the eaves of the house or under tall evergreens where the soil is likely to dry out. It is important to note, that the combination of dry soil and cold temperatures can cause serious freeze damage to garden trees and shrubs. In fact, in some of the drier areas of the garden, such as under the eaves or under tall evergreens, you may need to water in mid-December or mid-January, if you find the soil dry.
COVERING: This is one of the most effective ways of protecting the foliage of broadleaf evergreen shrubs. Rhododendrons, camellias, azaleas and early flowering plants will often benefit from being covered with some type of cloth material during extremely cold weather..
Start by placing three or four stakes around the plant being protected. Next drape some type of cloth material over the stakes, being careful that the cloth does not come in contact and freeze on the leaves. Notice I said cloth material, do not use clear polyethylene for this job, as it not only cuts off air to the plant, it also acts much like a greenhouse, taking plants from nightly lows to high daily temperature in a relatively short time period. This rapid temperature change can cause serious freeze damage or may be fatal to plants.
Any type of covering should only be left in place during the cold spell. As soon as the weather moderates or it begins to rain, remove the covering completely. However, leave the stakes in case it gets cold again.
Burlap, old moving blankets, sheets, Reemay or similar cloth or fabric materials are the best types to use as a cover over plants.
LIGHT SNOW COVER: Mother Nature actually provides the best blanket of protection in the form of a light snow. Up to two or three inches of snow not only insulates the ground around your plants it also provides a blanket of protection over the leaves.
On the other hand, it should be noted, that a heavy wet snow can cause considerable damage. As it tends to place to much weight on the leaves and branches, often causing them to break. And, in some cases even causing trees to break off. So if the snowfall is wet and heavy, you should make it a point to shake-off the excess snow before any damage occurs. Try to do this carefully so some snow remains as a winter protection.
ROSES: Mound mulch up over the base of rose canes, to a depth of 8 to 12 inches. Bark, sawdust and straw are among the best materials to use for this job. Pull the mulch material away in early spring. A frame of rabbit or chicken wire can be made around tree roses, then filled with straw to completely protect the stem and upper parts of the tree rose. Most climbing roses are very hardy and seldom need covering protection.
CONTAINERS: One of the easiest ways to give them winter protection is to simply take them into the basement of garage during a cold spell. (Avoid putting them into a heated room.) Then once the weather improves put them right back outside. Do not leave the planted containers inside all winter, unless you have a greenhouse or sun-porch, for them.
Remember containers are exposed to air on all four sides, plus the top and the bottom, so they can freeze very easily. And, exceptionally cold weather can damage the container too.
If the planted container is too large to move into the garage, during cold weather, you can mulch around the sides of the container. Simply mound bark or sawdust up around the sides of the pot, or wrap the container with blankets or packing. (Either way, this is not attractive, so even if you have to borrow a hand-truck, it's best to move the large container into the garage during coldest weather.)
CANE BERRIES: Berries like raspberries seldom need winter protection, however if you live in a very cold spot, you can mound 10 to 12 inches of mulch around the base of the canes. Straw is excellent for this, then in springtime use the straw as mulch between the rows.
TENDER PERENNIALS: Plants like chrysanthemums, hardy fuchsias, penstemons; and other tender plants can be covered with only about one inch of straw during a cold winter. (In a mild winter, this is usually not necessary.)
HALF-HARDY SUMMER ANNUALS: Stock and snapdragons are only two prime examples of annuals that will sometime become perennials and winter-over if given a little mulching attention. Straw, bark or sawdust are the best materials to use for mulching over these plants. Use only about one inch of mulch.
HALF-HARDY SHRUBS & VINES: This group would include: Bougainvillea, Euryops (Yellow daisies), Hibiscus, Gardenias, Mandevilla, Citrus, etc. In the Pacific Northwest and other areas where the temperatures dip below freezing, these plants should be treated as indoor houseplants over-winter.
OTHER ANNUALS: New Guinea impatiens, fibrous begonias (Wax Begonias), coleus and Abulton (flowering Maple) are just a few of the summer annuals that you can pot-up and bring into the home to use as houseplants. Then next spring, after all danger of frost is over, these plants could be once again planted outside.