Tucson CitizenTucson Citizen

Don’t be a drip . . . As trees grow, give them more water


With spring in the air and summer on the way, I want to remind everyone to think not just of the beautiful flowers and their exciting new garden, but also of the trees and shrubs that become the background of the landscape.

So often we talk with people who are worried about trees or shrubs. They were planted years ago and started out doing fine, but now they seem to get worse each year.

My first question is, “As the plants have grown, have you increased the amount of water they are receiving or, in the case of trees, enlarged the watering well?” Most of the time, the answer tells us why the plants are doing poorly.

I know that there are great landscapers out there, and ones that are not so great. In large part, it is the ones that truly don’t understand their craft that cause homeowners to misunderstand what is going on with their plants.

There are many different kinds of plants that we use in Tucson landscapes. If yours is a truly xeric landscape, the small plants (agaves, yucca, desert spoon, hesperaloe, etc.) can get by happily on very small amounts of water.

It is when we have a mixed landscape of xeric plants and moderate water use non-native plants and trees that we start to run into difficulties.

When a plant first goes to its new home in the ground, it has a relatively small root ball. If that plant is to grow well, it’s roots have to be able to spread out into a larger area.

There is an absolute truth that all plants know – roots follow water. If you have a basically desert landscape, but planted an ash tree for shade – they need different amounts of water. For that ash (or any other tree) to grow well, it must be able to grow a large root system. If it is getting a dribble of water every day or so, that water goes nowhere and neither do the roots.

I truly don’t believe there was a problem in Tucson before folks started using drip irrigation. Everyone who planted a tree made a large well around it and filled it with water, giving it more as it got bigger. You can still see beautiful, huge trees in the older areas with watering wells that have become so large and tapered that after 30 years of great watering and well expansion, there is just a gently tapered depression as wide as the tree’s canopy.

Do they waste water? Probably not. Trees do so many great things for us that the water use is offset by the plant’s ability to remove carbon dioxide from the air and transpire pure, clean oxygen. They also cool our yards and decrease our utility bills.

This is not to say that trees cannot be grown well on drip irrigation. They can. They need to have emitters added in ever expanding circles as they grow, and the systems need to be run for longer periods of time and checked for malfunctioning heads.

It is going to get hot soon. Make sure the oxygen and cool producers in your yard have what they need to do a great job.

Cathy Bishop, co-owner of Mesquite Valley Growers Nursery, has more than 30 years of gardening experience. E-mail her at familyplus@tucsoncitizen.com.


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