The holiday season is upon us. We all had our fill of turkey and fixings, Black Friday is finished, and Cyber Monday is just around the corner.  You have worked hard all year to make sure your trees look their best and now is not the time to stop.

Winter is often an overlooked season when it comes to working in the landscape.  Providing supplemental irrigation during the winter months can help sensitive plants make it through the winter a little less stressed and with less winter desiccation injury.

Not all plants are susceptible to winter desiccation.  Winter desiccation happens when the plants’ roots aren’t able to soak up enough water to replace the moisture lost through the leaves.  This often results in plants having areas of yellowish/tan colored leaves come spring.  Woody plants with shallow root systems are usually the hardest hit.  Spruce, fir, pine, arborvitae, yew, Oregon grape-holly (Mahonia), holly, and boxwood are some of the more common evergreen plants that would benefit from supplemental winter irrigation during extended dry seasons.

The plant’s location within the landscape can have an effect on its potential for winter damage.  Plants that receive reflected heat from buildings or walls will be more susceptible to damage.  The reflected heat from the building can warm up the area and plants surrounding it, leading to an increase in moisture lost.  Exposure to north and west winter winds can also have an effect.  Plants that are exposed to the winter winds will often only have desiccation injury on the side that is more open to the winds.

There are a few steps that you can take to prevent winter desiccation.  For starters, make sure that the plants go into winter well watered.  It may be too late for that this year, but it isn’t too late to provide supplemental water this winter.  There are some rules to providing supplemental irrigation in the winter.  Water should only be applied when the daytime air temperatures are above 40 degrees F.  Try to apply the water in the middle of the day and allow it plenty of time to soak into the soil profile before the temperatures drop below freezing.  If it is not given ample time to soak in, there could be a resulting layer of ice on the soil’s surface that could cause some damaging effects on the trees roots and possibly surrounding turf.

Timely applications of an antidesiccant on the most susceptible plants can also help to ease winter desiccation injury.  Antidesiccant products, like wilt-pruf, reduce the amount of moisture that is lost through evergreen foliage.  They coat the needles of the plant with a light weight polymer substance that prevents water from leaving the foliage.  These products usually last about 5 or 6 weeks before they degrade in the sun and elements.  Antidesiccant products are commonly put on newly planted trees, those that are exposed to winter winds, or those that receive reflected heat.  Aim to apply these products beginning around Thanksgiving and reapply throughout the winter.  For best results, antidesiccants should be applied when air temperatures are above freezing so the liquid will dry on the leaf surface.  If you mix and spray antidesiccants yourself, be sure to clean out the sprayer thoroughly immediately after the application.  These products can form a glue-like mass inside the sprayer that will harden in the lining and can clog spray nozzles.  A hot water and soap solution flush will help to prevent damage to the spraying equipment.

As we all know, there isn’t a ‘normal’ season in Nebraska.  Each year brings its own challenges to overcome.  Last year it was the summer drought, before that it was the holiday snow storm, and who could forget the New Year Eve ice storm.  Knowing your climate, plants, and what they require can help you to decide whether or not action needs to be taken.

For more information contact Elizabeth Killinger at elizabeth.killinger@unl.edu, 308-385-5088, on Facebook, Twitter, her blog at https://huskerhort.wordpress.com/, or visit the University of Nebraska-Lincoln Extension website: hall.unl.edu.