Plants Need a Good Drink Before Winter

By Ron Dieter, Sunnyfield Greenhouse & Gardens

November 15, 1999

If your landscape plants could talk, they'd tell you the recent extended Indian Summer will make winter difficult to endure. Although the days have been warm and pleasant, we haven't had any significant moisture in nearly two months.

In a "normal" year, the cool rainy days of fall replenish soil moisture, providing trees, shrubs, and plants with the moisture reserves needed to survive the winter. This is especially crucial for broadleaf evergreens, such as boxwoods and azaleas. Evergreen trees and shrubs actually transpire and give up moisture to the atmosphere all through the winter. Without adequate soil moisture, these plants can become severely desiccated, even freeze-dried.

So if you're looking for an excuse to be outside in the mild weather, here it is. Get out that garden hose and thoroughly soak the ground around your evergreens. To prevent the moisture from quickly evaporating, apply a thick layer of mulch over the soil around the plants.

While you're at it, your perennial plants and bulbs would enjoy a good drink too. Bulbs especially need moisture because they generate a new set of roots in the fall, getting ready to produce the foliage and flowers of spring.

Of course, Indian Summer won't last forever and temperatures will soon drop below freezing. Plants can then suffer from another form of moisture loss- that caused by salt injury. High salt concentrations make soil moisture unavailable to plants and even draws moisture out of root tissues. De-icing salts applied to sidewalks and drives wash into the soil and can injure sensitive plants nearby. Plants downwind from highways can be damaged by the aerial spray generated by passing traffic.

There are some steps you can take to minimize salt damage to your landscape plants. Apply sand or granular fertilizer to walks and drives in place of salt. If you use salt, you can leach it away by giving the soil a good soaking when it thaws. An application of gypsum will help control salt damage by displacing the sodium in the soil. In early spring you can hose off plants that may have been showered with salt spray during the winter.

Some plants are more tolerant of salty conditions and should be considered when landscaping near streets and sidewalks. Dwarf lilacs, most junipers, sumacs, and chokeberries will survive salty soils. Ash, cedar, honeylocust, and black walnut trees can endure saline conditions. There is a long list of perennials and grasses that will stand up to salty soils including sedums, coralbells, daylilies, iris, coreopsis, shasta daisies, bluestem, sea oats, switch grass, and maiden grass.

If you have plants near a drive or walk that have performed poorly over the past few years, it is possible salts are the problem. Consider replacing them with plants more tolerant of salty conditions.