Leaf Scorch
And the Benefits of Mulching

"The edges of my leaves are drying and the entire plant looks like it is dying." What can I do? This is a common complaint during the hot, dry summer season. The problem is leaf scorch. Leaf scorch is caused by one or several factors.

Drying wind - During periods of high, dry winds, moisture is removed from foliage faster than the roots can supply it. The result is scorched or withered foliage. Only protection from the wind can help in such cases.

High light intensity - Some plants cannot stand the bright sun of mid-summer in Texas. This is particularly true of trees and shrubs not adapted to the local environmental conditions such as most magnolia, dogwood, azalea, and maple.

Insufficient soil moisture – During dry seasons, watering should be very thorough. Merely sprinkling the ground around a plant until the surface is wet is inadequate.

When water and leaf scorch are mentioned together, many people think that water beads on the leaf surface act as a prism to concentrate the sun's rays and burns sections of the leaves. This is a totally false notion. First, the water droplets would have to form and retain a deep bead in order to generate a prism ray. Second, if such a ray could be generated, the damage would be a very distinct, circular shape rather than a scorching of the leaf's edge.

Last year, area nurserymen were challenged to produce one single case of leaf scorch caused by watering during hot weather. Not one single example could be found. Watering with scalding hot water will, of course, cause foliage burn, and there is some evidence that watering a drought-stressed plant with cool water can cause leaf bleaching, but the theory that watering in hot weather scorches foliage because of water acting as a prism is totally false!

Many times, newly established plants have not generated enough root system to uptake sufficient moisture to offset the rapid loss of water that occurs during hot, dry weather. Trees that are over 6 feet tall when they are planted are particularly susceptible to this problem. They should now be pruned back significantly (at least 1/3 of top removed) if they haven’t been cut back already. The foliage of affected trees should be sprinkled with a mist of water 2 or 3 times a day. Apply a layer of mulch around the base of the tree to stabilize water loss in the root zone.

Simply put, mulch is a layer of material covering the soil surface around plants. This covering befriends your plants in a number of ways.

- It moderates soil temperature and therefore promotes greater root development. Just like people, plant roots prefer to be cool in summer, warm in winter, and they can be, under a year-round blanket of mulch.

- It reduces evaporation of water vapor from the soil surface thereby yielding three important benefits. First, it moderates the levels of soil moisture, promoting root growth. It also means you don't have to water as often, which reduces both your workload and your water bill.

-Mulching reduces washing and crusting of the soil during natural rainfall or irrigation. Falling drops of water can pound the upper 1/4 of soil, especially a clay soil, into a tight, brick-like mass that retards necessary air and water movement to the root zone.

- It reduces disease problems. Certain types of diseases live in the soil and are spread when drops of water splash bits of infested soil onto the lower leaves. Mulching, and being careful when you water, can reduce the spread of these diseases. Mulching will also keep fruit clean while reducing rot diseases by preventing soil-fruit contact.

-I've saved the best for last. Most weed seeds require light to germinate so a thick mulch layer will shade them out, and your weed problems are reduced by at least 90%.

What can you use for mulch? Any plant material that's free and not diseased can be used. Weed-free hay or straw, leaves, grass clippings, compost, etc., are all great. Fresh grass clippings are fine for use around well-established plants but they should be cured for a week or so before being placed around young seedlings.

Mulch vegetable and flower gardens the same way. First, get the plants established, and then mulch the entire bed with a layer 3 to 4 inches thick. Work the mulch material right up around the stems of the plant. When you finish, you'll have a beautiful, even expanse of mulch highlighted by healthy, productive plants.

Recent research indicates that mulching does more to help newly planted trees and shrubs become established than any other factor except regular watering. Grasses and weeds, especially Bermuda grass, that are allowed to grow around new plants are terrible thieves of moisture and nutrients. Mulch the entire shrub bed. For new trees, apply mulch in a 4-foot circle. The layer of mulch should be 3 to 4 inches thick.

The epitome of effective hot weather gardening is the combination of drip irrigation and mulching. Simply cover the irrigation lines with mulch to reduce water usage, disease problems and gardening effort while you increase root development and plant performance. That's how to garden smarter, not harder.