It's Not How Much Water......

How can we mitigate the effect of population growth in arid climates and explore means of reducing our use of water without jeopardizing the health of our plants?

The number one reason people lose trees is too much water due to poor drainage and/or over-watering.

Over-watering has long been the number-one reason for loss of fruit trees. Over-watering does not always kill the tree, but it can make the tree weak and more susceptible to diseases and insects, stress that can prevent the tree from ever performing well. Proper planting and the use of compost and mulches or top dressings are the most important considerations for minimizing water usage.

Understanding a tree’s water requirements starts with the planting location.
The soil characteristics indicate what watering will be required.

Soil that has a sandy consistency and is easy to dig suggests a fast-draining soil that may require more frequent watering. On the other hand, soil that is hard and clay-like and not easy to dig suggests a heavy, slower draining soil. Planting in the heavier soils requires that certain steps be taken to ensure that the tree may be kept healthy with less water later in its life.

Start With Drip Irrigation................

An excellent way to achieve consistent soil moisture is to install a drip irrigation system. Starting with the right type of emitter is important. When first planting, use four 1-gallon-per-hour emitters evenly spaced around the base of the tree. Watering frequency should be based on tests which determine how much water is actually needed.

Run the system for one hour, then check to see how much area the emitters are covering and how deeply into the soil the water has penetrated.

For a one-to two-year-old tree, water should cover the ground in a three-foot diameter around the tree and penetrate to at least two feet deep.

As the tree grows, position the emitters further out from the base of the tree, so the entire area under the tree’s canopy is being watered.

Sandy or fast-draining soils lose moisture too quickly, so your goals are to cut down on evaporation at the surface and extend the time between waterings.

Always check with your local nursery to determine if there are recommendations for incorporating organic matter into the hole when planting.

In sandy or other types of fast-draining soils, the addition of organic matter (compost) to the soil will help to retain water around the roots of newly planted trees.

Most important is cutting down on surface evaporation.

This is accomplished with the application of some sort of organic matter to cover the surface of the soil.

Whether it is compost, mulch, hay or wood chips, the object is to keep the root zone moist to the surface. This also helps to keep the root cool in the hot months, thereby reducing the stress that can occur in hot weather. The accompanying reduction in moisture loss through evaporation minimizes the need for watering.

Fast-draining soils are not the norm. Most gardeners encounter slow-draining soils. This can be due to various conditions, the most common of which are heavy clay soils and soils with shallow hardpans. These slow-draining soils, if kept too wet, become deficient in oxygen. Lack of oxygen in a tree’s root system stresses the tree, making it more susceptible to disease and insect damage.

To prevent this and reduce the amount of water that is used, particular attention must be paid to how the tree is planted.

In any location where poor-draining soil is suspected, a raised bed planting is recommended. Do this by building a planter (best) or mounding (second choice).

Gardeners learn that it takes some time and effort to determine how often to water a tree in clay soil. Clay soils form crusts, giving the impression that the ground is dry, when in fact the soil right under the surface is still wet.

Watering in a poor-draining soil that is already wet is usually detrimental to trees.

Problems from poor drainage often begin in the hot part of summer when extra watering needs are assumed. An afternoon wilt does not always mean a tree needs water, especially in clay type soils. If a wilt occurs and watering has been frequent (once in 5 to 10 days), it is important to directly observe the soil moisture by digging down to at least 18 inches deep.

As with sandy soils, the goal with clay soils is to reduce evaporation and extend the time between watering. And, as with sandy soil, the solution is mulching.

By covering the soil with a top-dressing of some sort, the surface takes longer to dry out, which in turn allows moisture in the root-zone to work its way deeper through the soil. Top dressings are effective in cutting water needs in all soils, but especially in clay soils.

This keeps the complete root zone of the tree in a cool, more evenly moist condition.

One can more than likely tell by now that I think mulching a fruit tree is the best way to reduce the use of water. However, top dressings are important for more reasons than just water conservation.

Encourage Feeder Root Growth
by mulching.............................

There is an overall improvement of the soil around the tree which creates an environment for microbial activity, establishing a food-making zone for feeder roots to grow into. In fact, over time, this will lead to lower fertilizer needs to sustain a tree's good health.

I recommend maintaining the depth of mulch at 3 to 4 inches.

A yearly refreshing will ensure a continuous break-down of beneficial organic matter in the root zone tree.

There are many programs available on the subject of top dressings. By contacting a local university extension service you may find one near to you. Here are a few projects in which I have had the pleasure of participating.

Santa Barbara City College (Santa Barbara)
Headed by Jerry Sortomme, this program demonstrates the varieties that do and don’t do well in the Santa Barbara area (and similar climates). The project includes traditionally-pruned trees, high-density planting examples, test varieties, including deciduous and tropical, and aggressive use of top dressings. There are a multitude of plants, native and introduced, for specific purposes as well as a dedication to the Chumash Indians and a wonderful view of the bay.

Emma Prusch Park (San Jose)
A joint effort of the community of San Jose, the U.C. extension service and the California Rare Fruit Growers. This project includes a wonderful community garden, a large rare fruit tree germplasm repository, examples of high density planting and outstanding examples of the use of top dressings. This is truly a dynamic, happenin’ project and well worth a trip.

Fair Oaks Community Garden (Fair Oaks/Sacramento)
A U.C. Master Gardener program spearheaded by Chuck Ingles. This project is directed at the home gardener, featuring demonstrations of ways to grow and maintain a wide range of fruit varieties. This is a continuously expanding program with lots of support from the very knowledgeable Fair Oaks Master Gardener group. Included are examples of traditionally-pruned trees, high-density planting, and grape and berry growing. Top dressings and composting are integral to their methodology. The Master Gardeners have regular tours and classes; contact them for the schedule.

You can contact Ed Laivo to share information about other garden projects that demonstrate practical home garden use of fruit trees, composting and mulching, by email at ed@davewilson.com.