Last week we had three days in a row above 40 degrees F. With no snow cover, this was a perfect time to water shrubs, trees and perennials in the yard. The forecast for Central Wyoming for the first week of 2012 looks good for another opportunity for winter watering.
In the high plains, winter winds can be very desiccating as they are often coupled with little or no snow cover (as opposed to mountainous areas). For this reason, there are two main reasons to water perennials in the winter. The first is that dry soil heaves and contracts at greater rates than moist soil, damaging root systems. This is succinctly described in a UW Extension publication called Winter Watering.
The second and related reason is that the very fine, microscopic root hairs responsible for a plant’s water absorption are very fragile. Exposure to dry air and cold quickly kills these very important parts of the root structure. Some amount of winter damage is probably unavoidable, but winter watering will help minimize this. Two very convincing reasons to pull out the hoses when temperatures move into the 40’s and water your perennials this winter.
How do you know when you have watered enough? Most resources I checked said to evenly moisten the soil to a depth of 8-12 inches. Unless you have a very sandy soil or went into winter with an extended dry season, there is likely some residual moisture below 12 inches. Given the time restraints of winter watering – short days and limited hours where temps are above freezing, the goal of watering to 12 inches seems reasonable, but even if you can only water to 6 inches, I suggest you do it.
You can dig a few holes with a narrow spade to check your progress, or try the trick suggested on this Kansas State Research and Extension webpage of pushing a large screwdriver into the soil and feeling how deep it easily penetrates.