Keep garden soils moist during a drought
Prevent drought stress in your garden and landscape by checking soil moisture.
June 30, 2016 - Author: Gretchen Voyle, Michigan State University Extension
It may not technically be a drought, but many gardeners are acutely feeling the lack of rainfall where their gardens are concerned. When virtually no rain has fallen for months, it puts many plants at risk of dying if they are not adequately watered. When smart gardeners see perennials or annuals that are wilting, they know they should water them. But for trees and shrubs, they may have no idea that the soil is very dry and these trees and shrubs are stressed. Plants generally need 1 inch of water per week, but this guideline only works when there is some residual ground moisture, and we have none now.
Currently in Michigan there is no moisture in the ground to a depth of about 3 feet. The heat and lack of water can do a great deal of damage to trees and shrubs. Sometimes, like with evergreens, by the time the damage is noticed, it cannot be reversed. If the evergreen is turning brown, the chance to save it has passed. Michigan State University Extension has been receiving calls daily related to moisture stress.
Some people have a lawn irrigation system and feel that their trees, shrubs and plants are receiving adequate water. However, if the lawn irrigation system is set up correctly, it is only moistening the top 3-4 inches of soil, and if the grass is healthy and growing well, very little makes it past the grass roots. Most of the tree and shrub roots are in the top 18 inches of soil. Many plants are in the top 12 inches. The grass may look fabulous, but the trees, shrubs and plants could be in serious trouble. A lawn irrigation system is for just that: lawn irrigation. Our daytime temperatures are all over the thermometer. It is hot for several days and then it is cool. But the soil is still remains the same: very dry.
When watering trees and shrubs, just a hose can do an adequate job. Trees and shrubs must be watered all the way around the tree root area. That water is going to be picked up by the roots and transported up that side of the tree where it was applied. There is no internal plumbing to shift the water to any other locations. Watering at the trunk will only reach some of the roots. The roots fan out and for established trees and shrubs, they can extend out as far as the branches reach. That spot is called the dripline. For large trees, roots can go far beyond the dripline, possibly two times or more.
One of the essential tools smart gardeners should own is a rain gauge. These cylinders are put into yards and gardens to measure rain – if any ever falls. They can be bought for as little as $3 or $4. They do a much better job than pie plates or buckets strewn around to catch water and then measured. You want to be able to find 12 inches of moist soil when you check.
This rain gauge can also measure output from a lawn or garden irrigation system. When some gardeners are asked, “How much water was applied to your garden?” they respond with “Twenty minutes.” They have no idea how much water actually went down, just the time that the water was on.
The moral of this story is to check soil moisture. Only you can prevent drought stress in your gardens. For information on how to tell if your trees and shrubs have drought stress and what to do, read “Drought conditions begin to impact Michigan landscapes.” For information on helping your lawn during a drought, read “Helping your turf during dry and hot weather.”