Dry, Dry, Dry

By: John Degroot

September 4 2010

Dry, Dry, Dry - Garden Clippings for Sept 4, 2010

                My client planted the Ivory Silk Lilac Tree 6 years ago.  This spring it mysteriously died so he asked me to stop by and diagnose the problem.  Perhaps too much water was my first thought, but that made little sense, because the tree was planted in a raised garden and the soil was sandy.

                No other solution came to mind so I suggested that we inspect the roots when the tree was dug up to be replaced.  Just before leaving, I grabbed the tree’s trunk to see how firm it was in the soil, and to my surprise I pushed it over with little effort.

                “This thing has no roots” I quipped, “Are you sure it does not get too much water?”

                  “Not a chance”, he replied, “My automatic water system only gives water for 15 minutes every two days.”

                Case closed.

                  My client innocently caused the Lilac tree’s demise by giving it water too often.  His light watering caused the Lilac roots to remain near the surface.  If he would have unplugged his automatic sprinkler system, the tree’s roots would be encouraged to go deep in search for moisture.  A classic case of killing with kindness.

                My brother, Jack, who specializes in turf care, often expresses frustration with sprinkler systems that apply water too often.  He explains that the lawn becomes lazy, roots don’t go deep, and turf becomes vulnerable to unwelcome fungus and weeds.  In particular, he has seen an increase of Rough Bluegrass appearing in lawns, due in part to last year’s wet weather, and gardeners who react to this year’s drought by watering too frequently.

                “A deep watering every 6 days is far better than a quick watering every 2 days” says Jack.  “What holds true for turf also holds true for trees and shrubs.”

                Lambton County’s dry weather has proved challenging for summer of 2010.  Grass, trees, shrubs and flowers of all kinds are showing signs of stress.  Plants are putting up their own defense mechanisms by dropping some of their leaves prematurely and by closing their stomata, which results in wilting.

                  Particularly vulnerable are plants that have been planted in the last year or two and have not yet become fully established.  Other trees at risk are city owned and have been planted along city boulevards where the soil is poor and water is scarce.  Trees in public parks, church properties, school yards and other neglected areas might also be suffering.

                  Not all plant species are created equally.   Birch, Mountain Ash and Beech trees are intolerant of drought, while Maples and Oaks are hardly bothered.  In the shrub category, Hydrangeas hate dry soil, and Dogwoods follow close behind.  Summer phlox, Ligularia, Bugbane, Astilbe and Hosta don’t fare well in dry soils especially when planted in sun.

                Gardeners who have trees and plants that are suffering due to drought and stress would be wise to apply water generously and deeply.  A good technique is to set the hose at the base of a tree and let it trickle for an hour.  Equally effective is an oscillating or pulsating sprinkler running for a few hours to provide a thorough soaking.