Tips for winter care of trees and shrubs

With the garden season drawing to a close, it's awfully tempting to forget about your plants. But you should continue to water all woody plants - especially newly planted trees and shrubs and all evergreens. Helping your valuable garden trees and shrubs sail through winter starts with thorough watering in the fall.

Water your plants well until the ground freezes, and make sure you water enough through a dry fall. Your plants will need the equivalent of one inch of rain per week. (In a wet fall, you can relax.)

Evergreens and broadleaf evergreens (shrubs such as rhododendron and boxwood) don't lose their leaves, so they need a good store of moisture going into winter because they continue to transpire (give off water vapor) through the cold months.

Most winter damage to evergreens doesn't actually come from cold, but from the drying effects of late winter sun and wind. With the soil frozen hard, plant roots can't take up water to make up for moisture losses from transpiration and, as a result, dehydration can cause browning or burning of foliage.

Winterizing trees and shrubs: To wrap or not to wrap?

When considering winter care of trees and shrubs, don't go crazy with burlap wrap. It's extra work and doesn't look great.

After all, the whole point of evergreens is to give you something green to look at in the winter! Contrary to popular belief, most established evergreens hardy in your region don't need to be wrapped.

However, as with many things in gardening, there are exceptions. Some evergreens, such as dwarf Alberta spruce, are prone to winter-burn, so they should be covered, as should newly planted evergreens. (New plants haven't had time grow extensive roots that help them take up enough moisture to prevent excessive water losses.)

To make a windbreak around vulnerable plants, hammer four stakes into the ground and staple on a burlap covering. Never use plastic, or your plants could "cook" on sunny days. (Remember the greenhouse effect?)

More tips for winter care of woody plants:

• If your plants get salt spray from the road, burlap may help, but wrap them with a double layer, not a single layer. To avoid having to cover your evergreens, don't plant them near a road that gets salted, or plant salt-tolerant species such as junipers.
• Protect broadleaf evergreens such as rhododendron, pieris and laurel from the drying effects of winter sun and wind with an anti-desiccant spray such as Wilt-Pruf, which coats foliage with a protective waxy film. You can also wrap with burlap, if you must.
• To help preserve moisture, cover the root area of evergreens and broadleaf evergreens with a three-inch thick layer of leaf or bark mulch.
• Protect upright evergreen junipers and cedars from breakage due to ice and snow by wrapping branches with heavy string or mesh covers sold for this purpose. Once fastened into place, you'll hardly see the string or mesh.
• Protect young trees by putting plastic tree guards around the bottom of their trunks to prevent damage from gnawers such as rabbits and mice. Make sure the tree guards go high enough - over the snow line. (Remove them in the spring because it looks better and avoids the problem of the guards trapping moisture against the bark in the summer and attracting insects.)
• If rabbits are a big problem in your area, put chicken wire cages around the plants they find most tasty.
• Prevent rabbit and rodent damage with a repellent spray that you apply on lower trunks, branches and stems. Such products generally have to be reapplied after wet weather.