by Diane Sagers

CORRESPONDENT

This summer has been a scorcher with lots of dry weather, and the plants are feeling it even more than we are. You are probably finding evidence of this in your landscape.

Many of the magnificent trees that are providing the welcome relief of shade are suffering from the heat and dry air.

If you are looking at tree leaves with brown crispy edges -- which may in some cases also be yellow -- you are seeing summer leaf scorch. Sometimes leaf scorch affects a limb or two on one side of a tree or it can affect the entire canopy.

Particularly at risk are those trees with large, broad leaves. The trees most commonly affected around here are catalpa, silver maple, Norway maple, poplar, oak and horse chestnut. The heat forces rapid water evaporation from the leaves, often carrying it away faster than the roots and conductive tissue can replace it. As a result the leaf edges dry out and die.

Trees are placed under stress, but the condition is not usually fatal, unless they are deprived of water for a long period of time.

Do the best you can to supply adequate soil moisture. This does not mean following a water-every-day plan. For established trees, it does not mean watering every week. If the tree is in the lawn, do not expect the lawn watering schedule to provide all the water it needs, either.

The best option is to water very deeply right around the tree soaking the ground 3 to 4 feet deep. Likely this will not need to be repeated more than every three to four weeks. This does not require as much water as it sounds like it might. An inch of water will wet a loamy or clay soil about 6 inches deep. An inch will wet sandy soil about a foot deep.

Just because the soil surface becomes dry, it does not mean that water is needed. Check down in the soil to determine the need. Roots that receive too much water will be damaged and do not function to supply water to the leaves. The water draws in air as it soaks through the soil and that air is as important to root function as water is. If the roots are damaged by over-watering (and far too many trees here suffer from that), the leaf margins will dry out the same as if the soil were too dry.

You may find that birches in your landscape are suffering severely from the heat and drought. They may have one or more dead or dying branches or they may be completely dead. Although this was an extremely popular tree to plant a few years ago, we do not see urban forests filled with this variety. Birch trees would really rather live in Siberia or Canada where it is cool or cold all the time and where they do not experience drought. Regular fertilization helps prevent nutrient stress. Here, the trees need not only the appropriate amount of nitrogen, they need supplemental iron as well.

If your weeping birch is in the lawn, you may think that it receives needed water and fertilizer automatically as it is applied to the lawn. This care is actually quite the opposite of what the tree needs. Light, frequent lawn watering and feeding is taken by the grass, as it should be. Tree roots get little if any fertilizer or water from these applications. You need to use a bar or stake to punch a hole deeper than the grass roots and add nitrogen fertilizer during the late winter or early spring when the soil is still moist and somewhat soft and the leaves have not yet emerged. Just before new growth begins, add iron in the form of Sequestrine 138 or Miller's Ferriplus. Water heavily but infrequently during the summer months as described above.

Although most pruning should take place during the late winter to early spring months, dead branches in trees and shrubs can be removed any time. Cut them out near the trunk and dispose of them. Leaving branches that are dying or doing poorly attracts borers and other damaging insects.

You may find yellowed, iron deficient leaves on many other plants at this time of year, particularly on silver maples and peach trees. Grapes -- particularly concord -- also commonly suffer from iron deficiency. While our soils contain adequate amounts of iron, the mineral is tied up by the alkaline nature of our soils. Over-watering contributes to this problem. Watering deeply and infrequently helps resolve this problem to some extent.

The use of an appropriate iron supplement will also make a difference. Watering deeply and infrequently helps resolve this problem. The use of an appropriate iron supplement will also make a difference.

Miller's Ferriplus or Sequestrine 138 are expensive sources of iron, but when buried in the soil, they remain available to plants for two to three years. Follow directions to put it into the soil. Do not scatter it on top where the sun will decompose it. Iron sulfate or chelated iron may temporarily green any foliage you spray them on, but they are not very effective when they are applied to the soil for root use since they will be tied up by the alkaline soil.