1 - Newly planted trees will often exhibit stress in their first summer until they can develop a large enough root system to support the spring growth of shoots and leaves.

Q.

I planted a Texas red oak in my front yard back in March. It started really well, but this last month, with the heat and dry winds, it is not looking so good. I water it deeply and have fed it twice but the leaves are burning and drying some. The top of the tree is growing up but losing leaves. What do I need to do? I water it every few days? Shall I feed with something? My soil is pretty decent here in my yard. The Texas red oak is the only tree not looking good compared to other trees I have started. It does the get the intense Southwest heat.

- Leigh M.

A.

I suspect that as a newly planted tree, it does not have a root system sufficient to deal with the heat and dry winds this year. During the cooler spring weather it probably put on more leaves than it can support now in the heat, so it is dropping leaves.

There is a chance that the late freeze that hit much of eastern NM this spring may also be playing a role, but I suspect it is just the limited root system.

What to do? - Water regularly (this year probably once a week) over a large area to encourage development of a good spreading root system. As the root system develops it should begin tolerating summers with less apparent stress. If it is not in a lawn, use organic mulch to cover the soil under the branches (even beyond the extent of the branches if you wish). This should help conserve water, moderate soil temperatures, and encourage good root growth. Much of the root growth of trees occurs in the autumn and into the winter, but do what you can to encourage the roots even now. Do not fertilize. Nitrogen will encourage additional leaf and shoot production, further stressing the roots and producing this growth of leaves at the expense of the roots. If phosphate or potash is needed, they will not cause this problem. You can apply some nitrogen to provide for protein synthesis in roots in late fall after dormancy begins. After the air cools, the soil remains warm at root depth and the roots do much of their growing at that time.

You will probably continue to see stress this summer. Good monsoon rains will be helpful.

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.

Links:

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