Water in the winter for green trees in the spring
Fall tends to be a time for putting away hoses, rather than getting them out, but don’t get in too big a hurry if you have newly-planted trees or shrubs.
Tim Sime, one of the owners of Jolly Lane Greenhouse in Rapid City, South Dakota, said lack of winter moisture and temperature fluctuation are two of the major culprits when it comes to winter-killed plants.
But don’t let that stop you from planting new trees or shrubs this fall—just keep in mind that they may need water even after they’ve lost their leaves.
“Fall is a good time for planting,” Sime says. “For the most part, it’s no different than planting in any other part of the season, as far as the planting process goes. If you can dig a hole, you can plant a tree. As long as the ground isn’t frozen, it’s fine to plant.”
Fall planting is best done with container-grown trees and shrubs in our area, according to John Ball, SDSU extension forestry specialist, in an iGrow article about planting bare-root trees. “While bare-root trees can be planted in the autumn and spring in most of the United States, in South Dakota only spring planting is advised. Our harsh and dry winters can often injure tender fall planted bare-root trees. Bare-root plantings are limited to the spring time period between soil temperatures warm enough to allow for root growth (at least 45° F) and when the tree’s buds begin to expand,” he writes.
Sime advises amending the soil when planting trees or shrubs, unless you have unusually good soil—not typically the case in western South Dakota. Adding compost to South Dakota’s native soils will help improve both drainage and moisture retention, keeping the soil and moisture in contact with the roots.
“When we get to the point that we have freeze-up for winter, that ground needs to be saturated,” he said.
The danger for most trees and shrubs that don’t have established root systems comes with the 50 to 60-degree days in the midst of winter’s chill. While we may be basking in the sun, the thawing that begins can be deadly to plants. Making sure the soil around the roots is moist before it freezes can help offset the effects of these temperature fluctuations. “The moisture in the soil acts as an ice cube,” Sime says. “It keeps the ground cold even when the temperature goes up.” The goal is to prevent change in the soil temperature as much as possible.
On those nice days, Sime suggests getting out the garden hose and letting it slowly trickle around the trees, or drilling a few small holes in a five-gallon bucket, and filling that and setting it beside the tree. “If the water is soaking in, the tree needs it. If it’s running off, you don’t need to water,” he says. But he also says it’s always better to have too much than not enough.
Mulch can be another way to help keep trees alive over the winter. Wood chips or river rock help hold in the moisture that would otherwise be sucked out by winter winds with no snow cover.
If you’re not sure if watering is necessary, Sime suggests pushing a metal rod or stick into the ground as far as you can—at least six to 12 inches, to see where the moisture level is. The goal is to make sure there is moisture around the roots. When in doubt, water.