Water Now To Help Mitigate Dry Winter

The USDA has made it official: most Colorado Front Range counties have entered into the first phase of the five phase drought scale. The Denver Metro area has only had 2" of precipitation since October and the national weather service is estimating the "La Nina" in the central tropical Pacific Ocean will cause more dry, warm weather for the next three months. If that holds true, our gardens could suffer mightily if they aren't prepared for a stressful spring.

The warm, windy weather we've been having is especially hard on evergreens because these trees continue to transpire throughout winter when humidity is especially low. The dry air causes moisture to evaporate through the leaves, which draws more moisture through the fine root hairs, up through the phloem evaporating through the leaves, continuing the transpiration process whenever the sun is shining and the temperature is warm. The problem comes when soils become so dry that the root hairs begin to desiccate, limiting the amount of water that can be absorbed and causes tissue die back (starting with the buds for the new year's growth). When a new supply of moisture becomes available it takes awhile for the tree root mass to recover, slowing growth and keeping the tree in a stressful state.

This isn't a problem if the soil is frozen, but in order for the soil to freeze it must have moisture. In this region, soil gets hyper dry because wind, low humidity and intense light combine to compound the effects of infrequent precipitation. As the period between waterings (through precipitation or human intervention) extends, soil moisture is depleted through evaporation, transpiration, and to some extent, gravity. The speed with which this occurs depends upon the temperature, humidity, solar intensity, and wind velocity. Since we are attempting to alter
nature by growing alien plants with low tolerance for desiccation, it becomes necessary to intervene in the lives of our landscape.

Now that spring has arrived it's critical that there is moisture in the soil as the plants start to come out of dormancy and put on foliage. Water plants after the top 1/2"-1" of the soil is dry to the touch, but don't supersaturate the soil. Roots need oxygen as much as they need moisture, so for clay soil water in short spurts--5-10 minutes at a time--then give the moisture several hours to percolate into the soil before adding more water. Sandy soils are so coarse the water doesn't collect the way it does in clay based soils, but 30 minutes is plenty of time when using a frog eye sprinkler. Now is a great time to add more mulch, when plants are still small and foliage hasn't filled out. The mulch, which works best when about 3" deep, will help slow surface evaporation and shut out light for germinating seeds.