Trees Planted in Grass Need Extra Water

Q. I had a 3 year old mesquite tree in my front yard that just blew over in the wind today.The original landscapers planted a tree without a drip system. I have an area of grass around the tree and they told me in the past that that is sufficient to water a tree. Today the landscapers that came to cut down the tree told me it fell because of the roots being at the surface. Do you recommend putting in the drip line? I can tell you the soil under the tree was very moist from the sprinklers. I have attached a picture of the felled tree. Any suggestions for a tree that would be sturdy to the wind? The original tree planted was a glossy privet that died after the first year. It was replaced by the mesquite. I have to plant something in the 24 inch box size per HOA rules.

Mesquite tree that blew over

A. I am sorry to hear about your tree that blew over. This can be a problem sometimes with trees that are planted in or near lawns and rely only on lawn irrigation. Lawns require shallow irrigation that are frequent. Trees and large shrubs require a larger amount of water applied less often. Be very careful of planting trees that originate from deserts and used for desert landscaping (examples are acacia and palo verde) planted in the lawn. This usually does not work well. Trees that are suited for lawn areas are those that are not desert trees.

Trees and large shrubs getting water only from the lawn will fight for the shallow irrigations of the lawn. If you are an efficient lawn irrigator, the tree will have a difficult time getting the deep irrigations it needs for deep rooting. When trees are planted in large turfgrass areas, such as golf courses or parks, the trees always grow faster and perform better if they are supplemented with water for the first few years. After three or four years of successful growth, you could eliminate the hose irrigations around the trees except perhaps during the hottest parts of the summer.

Mesquite roots can good deep if given a chance. This is a native mesquite in Zacatecas, Mexico, near a river. The roots had found moisture from the river but not at the surface and so were forced to go deep where moist soil was located.

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.

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. It also helps, as you have done, to keep that area free of grass and weeds. If you can remember to water with a hose, particularly during the heat of the summer, you can save yourself the expense of installing a new drip line.

Mesquite trees are what we call riparian tree species. Unlike Palo Verde or acacia in the desert, Mesquites are only found near waterways. They grow when water is available and stop growing when water is not. When water is constantly available, they constantly grow. When Mesquites get water they can grow quite rapidly, as much as 8 feet in a single year. 

Honey mesquite with mistletoe in the Mojave Desert in North Las Vegas

This is a problem when they receive constant watering because their tops grow faster than their roots and this contributes to blow over. For this reason Mesquites are not a good choice for a lawn area but are more appropriate for a desert landscape. In lawn areas stay away from desert trees. Trees like many ash, Locust, honey locust, privets, and others are not desert trees and they will survive in the lawn much better.

Personally, I think you are better off without the lawn unless you have a use for it. You can substitute green groundcovers and achieve a similar look to a lawn. When you plant trees and you do not have a lawn make sure that you surround the trees with some smaller shrubs to help keep the trees irrigated. Focus on smaller trees that are in scale to your home. Don't put in 40 foot trees if you have a single story home. 

Take advantage of the shade they give and put them so they shade the south and west walls and provide shade to where you have outside activities. Trees should probably not be planted just for looks in the desert. They should also have something to contribute to your comfort as well. So remember to keep your trees small, use desert adapted trees whenever possible, minimize the use of tall trees and shrubs to reduce your water use and to make sure they contribute to your home environment and your outside living environment.