1 - It is not uncommon for a newly planted tree to lose leaves in the middle of the summer.

Yard and Garden July 14, 2012

Q.

I have a new Linden tree (planted the first week of December by a very reputable tree company in ABQ). It is about 15 feet tall with a trunk about 5 inches in diameter. It has done GREAT since planting, but a week and a half ago, leaves began turning yellow, then dried up and turned brown, fell off. At this point, the tree has about one-half the foliage the tree started out with in the spring. The tree company representative dropped by my house last week and left word that the tree is "heat stressed" but left no info on what I should do about it. I water twice a week, one time filling up the dirt "bowl" surrounding the tree trunk and one time with a trickling hose left on for 10 hours. Can you give me any advice? I LOVE this tree and cannot stand to watch it die.

Rebecca L.

Albuquerque

A.

It is not uncommon for a newly planted tree to lose leaves in the middle of the summer. Even some older, well-established trees will dispose of leaves during the summer. In this case, the tree produced numerous new leaves in the spring, but because it was recently planted, the root system was not adequate to keep up with the water loss by the leaves as the weather warmed. The response of the tree was to dispose of leaves, reducing the demand on the roots to supply water. It is unlikely that all the leaves will drop unless the tree has been overwatered to the extent that root rot reduces the ability to the roots to provide even a little water.

The monsoon rains have begun, bringing a little rain, with higher humidity and cooler temperatures for now. This should help your tree. Proper watering (once a week in clay and loamy soils and twice a week in sandy soils) should be adequate for now. An organic mulch over the root zone will help cool the soil, conserving water and reducing the number of times you must irrigate. Check the soil by pushing a long screwdriver into the soil to determine when the soil dries. The quantity of water you need to supply should equal or exceed the volume of the container that contained the rootball of the tree when it was planted.

As the tree grows (next year and subsequent years) you can reduce irrigation to once every two weeks to 10 days. As the tree grows, the roots that actively absorb water and minerals grow away from the trunk so you will need to move the location at which you supply water to the tree outward as well. This means you will be watering the established tree at the dripline (below the ends of the branches) and outward from that location. However, this year you need to apply water in the area of the planted roots and slightly outward to provide moisture for outward root growth. As the tree establishes, more water will be needed, enough to moisten the soil to a depth of 2 to 3 feet. When you irrigate the tree, it is important to moisten the soil to the same depth each time you irrigate. Otherwise, roots will suffer and the top of the tree will also suffer.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

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