Dr. Grow: The ways of watering

Watering is one of the most critical, if not the most critical maintenance practice in gardening. In fact, in all the textbooks I have read on gardening, greenhouse growing, etc., one or more chapters are reserved for watering practices. In fact, each one of them states -- usually in bold print -- your best grower, gardener or landscaper should be the one who makes all the decisions on when and how much to water.

If your most experienced person on staff is the one who should make all of the watering decisions, you can bet watering is important. They are probably being paid more than anyone else in operation.

Good watering essential

What's the big deal about watering? Surely you can find a high school student, a college student or the kid down the street to do your watering. It can't be all that hard. After all, all you have to do is hook up the hose, turn on the spigot and let the water fly.

Let's take a look at the subject of water and plants. Of course, plants require water for germination, cell enlargement, chemical reactions (both as a chemical in the reaction and a medium in which the reaction occurs) and transpiration. The source of this water is moisture in the soil that is absorbed by plant roots. So far, everything is very elementary.

Suppose your plants aren't getting moisture because of the lack of rain. If the moisture stress is bad enough, your plants will begin to look limp. There isn't enough moisture in each cell to keep it fully inflated. If moisture stress continues, then leaves will tend to turn brown, or burn along the edges. Usually the newest leaves, which require the most amount of water, will exhibit these signs first. If moisture stress continues, leaves will begin to shrivel and fall off. Finally, death will occur.

Now if you continually overwater your plants to make sure that they do not suffer from lack of moisture, plant roots will tend to rot and become non-functional. If plant roots are non-functional, then water cannot move up into the plant. Your plants will begin to look limp. Then the leaves will tend to turn brown, or burn along the edges. Finally, leaves will begin to shrivel and fall off and death will occur. It sounds just like the symptoms exhibited during a drought.

No formula for watering

People always ask me to tell them how much and when to water. They think there is some formula you can use. They want to know how many gallons to give a plant and on what days to water a plant. Unfortunately, these formulas don't exist. A plant's moisture requirements will always depend upon the moisture demand of the plant.

Let me give you some examples to explain the above paragraph. If the day is windy, warm and sunny, a plant will transpire a lot of water. Therefore, the plant needs a lot of water to replenish the moisture lost during transpiration. If the day is calm and overcast, a plant will not lose as much moisture due to transpiration. Its demand is much less on this day.

The only sure way to determine if a plant needs water is to use the finger test. Stick your finger two to three inches into the soil around the plant. If the soil is moist, then don't water. If the soil is dry, then water. Again, if plants are overwatered, their roots will rot, and moisture stress within the plant will result. The finger test is the universal moisture test for newly planted shrubs, plants growing in pots or newly seeded lawns.

Tips to keep in mind

There are some other things that you need to keep in mind while watering.

* Keep water off the foliage as much as possible. Free water standing on leaves, especially during darkness, results in high humidity levels around your plants and encourages plant disease development.

* Water underneath plant foliage if at all possible. Get the water on the soil and not the foliage. If you must water over the top, plant foliage will always get wet.

* Be sure to water early enough in the day so the free water standing on plant leaves will evaporate before evening. Always water during the morning hours.

* Make sure you water your plants with enough water that the moisture completely soaks through the pot the plant is growing in. In the case of a plant growing outside in soil, make sure that you water enough so that moisture goes into the soil six to 12 inches.

* After thorough watering, allow root substrates (soil or potting mix) to dry out before you water again. Watering too frequently will promote root rot.

* Also, Army worms are beginning to take a toll on not only wheat and pastures but also on lawns in town. If you find them in your lawn (they will number in the thousands), use diazanon, dursban, malathion or cygon. You can spray the lawn or apply a granule. In either case, water the lawn after the application. Make sure that you water the lawn and fertilize it after you have treated for army worms. Your lawn will be under stress, and you need to provide adequate moisture and nutrition for it to recover.

I have seen several examples of lacebugs attacking azaleas. If your azaleas look off color, inspect the leaves for the small insect. It is about one-sixteenth inch long, with clear wings that have black spots on them. The undersurface of the leaves will also be covered with tar spots. If you find lacebugs, spray your azaleas with cygon, diazanon or dursban. Make two or three applications about a week apart. Make sure that the spray gets on the undersurface of the leaves. You should also provide adequate moisture and fertilizer so your plants can recover from the infestation.