TAHOE/TRUCKEE — Of the many challenges that face Sierra gardeners — heavy snow, cold temperatures, extreme temperature fluctuations, summer frosts, absent topsoil, low humidity and more — the most destructive may be winter drought and freeze drying.In other winters similar to this one, where there has been little snow or rain and the temperatures are very low, many landscape plants and even native plants have suffered.“When we finally charged the lines and ran the irrigation system for a couple of hours last Friday, people were actually pointing and laughing as they pulled off I-80,” said Eric Larusson. “It really is no laughing matter. We have been spot watering here and there on the warm days ever since the daytime temps have been in the mid 40s and above. The plants are dormant; they’re not dead yet. They can dry out and die without significant natural precipitation or supplemental watering.”Brent Thrams of Acanthus Studio, a respected landscape architect and planner with many projects to his credit in Truckee and Lake Tahoe, tells his clients: “Winter drought resulting in freeze-dried plants is the number one cause of plant mortality in the Tahoe Truckee area. “Even the natives get freeze-dried; we were at 7,200 feet (above Emerald Bay) and I saw lots of desiccated and wilting native evergreen shrubs.”Larusson and Thrams agree that occasional winter watering will be necessary until snow covers the ground. In sunny locations where snow has been gone for at least two weeks, watering twice a month is probably enough depending on the soil, the slope and the depth of protective mulch.“As cold-hardy plants freeze, water moves out of the cells into the intercellular spaces. This increases the solute concentration in the cells, and lowers their freezing temperatures. This shell of ice helps protect the cell,” Larusson said. “When the plant is exposed to long periods of dry air and sun, the ice between the cells sublimates away (ice to vapor), and this allows the little remaining super-cooled moisture inside the cells to be dry-out. The result is irreversible drought and cell death.”Shady portions of the landscape can be a bit more tricky. It is very important that water not pool nor completely saturate the soil and then freeze. Oxygen is as important to roots as water is and a layer of solid ice can actually suffocate roots and the many other essential soil organisms. Once a month is enough watering for shade gardens as long as the soil absorbs the water.“It is probably easier, in most cases, to thaw out a hose and water by hand or with a sprinkler,” Larusson said. “I have also used a bucket or watering can. Make sure you disconnect hoses from hose bibs and drain them before nightfall. It should go without saying that if a full irrigation system needs to be turned on, make sure that it is shut off and drained well before afternoon cooling occurs.”According to Marianne C. Ophardt of Washington State University Cooperative Extension, people should apply the water where it counts the most ... in the root zone. Consider that established trees have roots that go out at least as far as the tree is tall and usually further. It is in the “dripline” and just beyond where most of the water should be applied. Water applied at the tree trunk base is wasted because there are no water absorbing roots there. Watering recently planted trees and shrubs is a different story, Larusson said.“Their roots don’t go out that far yet,” he said. “In this case you will want to water the root ball zone and just beyond. The aim is to water where the roots are.”As Brent puts it, “The plants are not really using much water this time of year. But this dry cold air pulls moisture out of the soil and is desiccating to plants. You are just trying to keep some moisture available for the plants.”According to the Colorado State University Extension, “lawns also are prone to winter damage. Newly established lawns, whether seed or sod, are especially susceptible to damage. Lawns with southern and western exposures need to be watered enough to moisten the soil in 8-10 inches deep or deeper.”Furthermore, with trees and Shrubs, CSU Extension also says: “As a general survival rule, apply 10 gallons of water for each diameter inch of the tree. For example, a two-inch diameter tree needs 20 gallons per watering. Newly planted shrubs require more water than established shrubs that have been planted for at least one year.“The following recommendations assume shrubs are mulched to retain moisture. Apply 5 gallons two times per month for a newly planted shrub. Small established shrubs (less than 3 feet tall) should receive 5 gallons monthly. Large established shrubs (more than 6 feet) require 18 gallons on a monthly basis. Decrease amounts to account for precipitation. Water within the dripline of the shrub and around the base.”— This article was submitted by Eric Larusson, botanist/nurseryman with Villager Nursery in Truckee. The Villager recently sent out a newsletter to its mailing list clients to let them know how important it is to water (you can view a copy on at www.villagernursery.com).
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