Question: I had a 3-year-old mesquite tree in my front yard that just blew over in the wind today. The landscapers planted it in the grass without a drip system. I was told watering the lawn would be enough for the tree. Today, the landscapers told me it fell because of the roots being at the surface. Do you recommend putting in the drip line for a new tree?
Shallow roots can be a problem with trees that are planted in or near lawns and rely only on water from a lawn. Lawns require shallow irrigations that are frequent. Trees and large shrubs require a larger amount of water applied less often.
Be careful of planting trees that originate from deserts and are used for desert landscaping in a lawn (examples are acacia and Palo Verde). These usually do not work well surrounded by grass. Trees that are suited for lawn areas are those that are not true desert trees. Examples of these might be several of the ash, locust, ornamental plum, privet and others.
Trees and large shrubs getting water only from the lawn will fight the lawn for the water. Grasses are much better at getting water from soils than trees or shrubs, and these plants will lose. If you are an efficient lawn irrigator, trees will have a difficult time getting the deep irrigations they need for deep rooting. When trees are planted in large turfgrass areas, such as golf courses or parks, they always grow faster and perform better if they are supplemented with water for the first few years.
Some golf course superintendents would send out a water truck once every week or two to flood the area around the tree with water. This encouraged deeper rooting and kept the lawn from robbing the tree of its shallow water supply. It also got the trees off to a good start.
You can do the same thing with a hose. When a tree is planted in the lawn area, it is best to leave a shallow depression around the tree 3 to 4 feet in diameter. This can be a basin for flooding the area around the tree every week or two with a hose.
After three or four years of good growth, irrigations from the hose could be eliminated except perhaps during the hottest times of the summer.
It also helps to keep the area around the tree area free of grass and weeds. Grass surrounding the tree means mowers and line trimmers will be used right up against the trunk. Mowers and line trimmers to control grass around a tree trunk leads to trunk damage, future disease problems in the tree, slow growth and eventual decline.
If you can remember to water occasionally with a hose, particularly during the heat of the summer, you can save yourself the expense of installing a new drip line.
Bob Morris is a horticulture expert living in Las Vegas and professor emeritus for the University of Nevada. Visit his blog at xtremehorticulture.blogspot.com.