Hi, I have a lot of two year hybrid poplars that we've planted for a wind break and the leaves near the trunks are beginning to turn yellow. I've read that this can be because of lack of water or too much water or not enough fertilizer. It's July and we water them every day because of the 90+ temps. Any suggestions?



It sounds like too much water.  I prefer deeper and less frequent watering, normally established trees need a good soak every week to 10 days.  Also, frequent watering does not force the tree to grow deep roots that go after water and will sustain a tree through hot days.
Frequent watering also washes away the nitrogen so a tree will rob nitrogen from older leaves to keep growing.  This best explains your described your situation.  If it were not enough water you would see browning of outer leaves especially those on the south and west side that get the brunt of wind, sun, and warm temperatures.  Slowly cut back on your watering intervals but increase the amount.  let the hose run longer but put more days between watering.  We don't normally encourage fertilization of trees, especially not in the heat of the summer where it encourages lush green growth.  Spring and  late fall would be better.

Posted on 16 Jul 2009

David Drake
County Director, Agriculture and 4-H Youth Programs Agent

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