Answer: Blackened leaves can be due to slight frost damage or by wind damage. The frost damage may have occurred on a night in which temperatures at location of most thermometers registered temperatures above freezing; the frost may have been localized to small pockets.
Young leaves in the spring are often very tender and subject to damage from the winds which develop during our warm desert days. Temperatures can rise from very pleasant temperatures to rather warm mid-day temperatures. These warm days following cool nights, when combined with our frequent spring winds, can cause rapid desiccation of the leaves. The leaf margin is the most likely injured part of the leaf. This desiccation can occur even if the soil has adequate moisture because the wind can draw water from the leaves faster than the tree can move it from the soil into the leaves. Very young trees may exhibit symptoms because they are smaller, and also because they have trouble moving water through the plant to resupply the leaves. Newly transplanted trees, with limited root systems, and those which have just begun rapid growth after a couple of years establishment following transplanting may be the most likely to show the symptoms. However, under the right conditions this spring wind desiccation injury can occur in larger trees as well.
As long as the tree appears to be healthy and fruit production is normal, there should be little to worry about. This early in the year, a single deep watering should suffice. As temperatures climb, twice a week will be appreciated by your trees.
Best wishes with your new trees!
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