For Release June 4, 2006

Evergreen Trees Need A Drink About Now

 

AGRI-VIEWS

by Chuck Otte, Geary County Extension Agent


Since the first of the year, we have one month that had normal precipitation. For the first five months of 2006 we are 4.6 inches below average. We have had less than two thirds of normal precipitation. To put it bluntly, we are very dry. Now let’s add another factor to the scenario. We have had above normal temperatures during all five of those months, in fact we have had monthly mean temperatures above average for the past 22 months now. So it’s not only dry, it’s hot too! What we are starting to see now, is drought damage to evergreen trees. That damage could well have occurred back in January or February, but the problems aren’t being seen until now.

            

If you have a tomato plant in your garden, or a geranium plant in a pot on your deck and they get too dry, you know it because they wilt. Have you ever seen a spruce, pine, cedar or juniper wilt? You won’t, because it’s just not their nature. Which is really too bad because if they could wilt, homeowners would know to water them. As it is, we often don’t know that an evergreen is undergoing drought stress until parts of the plant start to die, and then it’s too late.

            

Even worse than dying plants, are stressed plants. Stressed Scots Pines are more likely to be infected with borers and those borers will carry the Pine Wilt Nematode. Stressed plants are more attractive to insects of all kinds, are more likely to get disease problems and all of these factors are going to lead to a premature death. The bottom line is that if you have evergreen trees in your landscape, they need a drink just about now!

            

Now let’s move on to myth busting. When I was growing up, and I’ll bet it’s the same for many of you, it was always implied that what you see above ground, with a tree, pretty well mirrors what’s going on below ground. Well, this is just WRONG! Most tree species do not have a tap root, as we have often thought they did. In fact, somewhere between 80 and 90 percent of the functional roots of a tree are in the top 18 to 24 inches. In some of our soils, those are probably restricted to the top 12 inches of soil. Even for trees that do have a true tap root, that tap root doesn’t do much other than anchor the tree. All the action is occurring in that top foot of soil. We have also found that tree roots extend much further out than the ends of the branches, which is what we used to think. The roots often extend two to three times further out than the drip line or ends of the branches.

            

When you water a tree, the best way is NOT to use a deep watering probe. Most of these put the water clear below where the tree can really use it. The best way is to place an open hose out at about the drip line and let it run, at a slow trickle, for several hours. Letting it run all day would not be a bad idea for a large tree. Check on it every few hours and if you have water that’s running off or pooling up, you will want to move the hose to a different area. Try to water at least two sides of the tree, although four locations would be even better.

            

If you have a lawn sprinkler system, it may not be putting enough water on to get the moisture deep enough so the tree roots can utilize it. A thick stand of turf will steal a lot of water in the top couple of inches before the moisture even has a chance to get down to the tree roots right below, especially if you are watering a little bit every day. Go ahead and supplement that with an open hose. If it stays hot and dry, then plan to water those evergreens once a month, and that would be fall and winter time too! Evergreens never really get to go dormant!


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