KC Gardens

Plants get thirsty even in winter

A bubbler can help slowly soak the ground under trees and shrubs.
A bubbler can help slowly soak the ground under trees and shrubs.

It’s dry. Moisture has been almost nonexistent since late summer. Last weekend’s dry snow was little help. The U.S. Drought Monitor has placed us in the abnormally dry category, and the National Weather Service indicates fall was one KC’s driest on record.

We don’t usually think about the effects of drought on our plants during the winter since they are dormant. But dormant plants use water, and lack of hydration will lead to death. The problem is we don’t see the symptoms — wilting, leaf drop or browning — until spring growth begins. By then, watering is too little, too late.

Winter watering is not a pleasant chore. It’s no fun to drag around hoses in the cold. But you will pay the price in discomfort either now or later when you must replace a dead plant. You can water in winter any time the temperature is above freezing, and the soil is not frozen.

Plants most at risk

Evergreens and younger, less established plants are in the most peril. Evergreens with needles tend to use and lose more water more rapidly and to have shallow and less vigorous root systems. Evergreens such as spruce are not native and aren’t as adaptable to our combination of cold and dry.

Younger plants, those transplanted in the last three to five years, have limited root systems, which makes it difficult for them to pick up the needed moisture. This applies to trees, shrubs and even flowers, whether evergreen or deciduous.

How much to water

Knowing how much water to apply is more of a guessing game and can be time-consuming. It is no fun holding a hose outside in the cold. Your goal is to thoroughly soak the entire root zone.

Winter watering of trees and shrubs is best achieved using a hose and slowly flooding the area under the dripline of the plant.

Another way to measure is in gallons applied. This works best for small plants. For example, for each inch of trunk diameter of an establishing tree, apply about 10 gallons of water. Use this same guideline for every 2 to 3 width feet for a shrub.

Unfortunately, this does not work for a mature spruce. Soaking may require moving the hose around the root system for several hours or more.

How often

Water is not used in great quantities or evaporate as quickly in winter. A deep soaking should last for several weeks or more before another application is required. The best way to know when to reapply is to dig around in the soil and check the moisture level. Avoid overwatering — saturated soils also adversely affect the plant.

Don’t leave the hose exposed outside when you’re finished: It will freeze and rupture. Winter watering is not complete until the hose is drained and detached from the faucet.

Dennis Patton is a horticulture agent with Kansas State University Research and Extension. Got a question for him or other university extension experts? Email them to garden.help@jocogov.org or visit KCGardens.KansasCity.com