Landscape Management

Water Quality: It's not just a drop in the bucket-you can make a difference!

The landscape of Delaware is changing. As forests, fields and farms give way to residential developments, roads and parking lots, the natural system that buffers the effect of dry periods on the water supply is destroyed. There is no doubt that periodic water shortages and resulting water restrictions will occur with increasing frequency and severity. If landscape water use is not reduced in the future, water restrictions will come sooner, with more frequency and, probably, with more clout. A better solution is to begin practicing water conservation principles now, before they are mandated.

Landscape Planning

"Xeriscapes" is a new term for planned, drought-resistant landscapes. By limiting lawn areas, using alternative surfaces, grouping plants in beds and selecting drought-resistant species, you can reduce water demand. Instructions for designing a drought-resistant landscape can be found in the fact sheet Landscape Design for Conservation. Suggestions of drought-resistant species can be found in the fact sheet Plant Selection for Conservation.

Reduce water use by:

  • designing a xeriscape
  • selecting drought-resistant species

The Planting Process

In recent years, researchers have found that small to mid-sized trees have the best chance of becoming established in the landscape. Much of the root system is lost when a tree is transplanted. Newly transplanted trees have trouble absorbing the water necessary for survival and growth. Smaller trees become established more quickly than large ones. Their roots spread throughout the soil and begin to absorb water more efficiently. A larger tree undergoes a much greater transplant shock than a small one and does not begin to grow as quickly.

Fall is a very good time to plant deciduous trees and shrubs. Spring-planted trees are under the extra stress of supporting an emerging leaf canopy, with high nutrient and water demands. In fall, their energy can be devoted to establishing the feeder root system. Evergreens, however, are best planted in spring since they make little root growth in the fall.

Avoid planting during periods of drought. Newly planted trees require water weekly. Take advantage of the natural rainfall in the fall or spring to provide most of the required water.

Prepare a planting hole that will encourage rapid spread of the root system into the surrounding soil. Dig out a broad, saucer-shaped depression two to three times the width of the root ball.

It is not necessary to modify the soil in the planting hole. The tree must ultimately grow in unenriched soil, the roots circle the planting hole and do not spread into the natural base soil. By digging a wide hole, you incorporate air into the natural soil and encourage root spread.

When planting, dig only a few holes at a time, and dig only as many holes as can be planted that day. As a hole sits unplanted, the available soil moisture is lost at that depth and is difficult to replace. Use a hose to trickle water into the hole and tamp the backfill. This prevents the roots from finding dry pockets of air and soil in the early establishment period.

After the hole has been filled, create a basin wider than the root ball to hold water while the plants get established, and fill it with water. Do not overwater newly planted trees and shrubs. A tree may wilt if the planting hole is constantly water- logged and oxygen-depleted.

Finally, cover all newly planted trees and shrubs with a 2- to 3-inch layer of mulch to retain soil moisture and keep down competitive weeds.

  • Plant small- to mid-size trees for easy establishment.
  • Plant in the fall (or spring) and take advantage of natural rainfall.
  • Plant trees and shrubs in a broad, saucer shaped depression, two to three times the size of the root ball.
  • Dig planting holes just before you are ready to plant.
  • Create a basin around the base of the plant to hold water.
  • Cover the soil around all newly planted trees and shrubs.
  • Cover the soil around all newly planted trees and shrubs with a 2- to 3-inch layer of mulch.


Mulches conserve soil moisture by reducing evaporation from the soil surface. Mulches also control weed growth and reduce erosion and soil compaction.

Mulches are divided into two major groups, organic and inorganic. Organic mulches last one to three seasons and then must be replaced. Some types of organic mulch form a crust that inhibits water percolation. Periodically rake the mulch to break up any crust that has formed.

Remove or incorporate decayed organic mulch into the soil before adding more mulch. Organic mulches include straw, leaves, manure, pine needles, leaf clippings, shredded bark, wood chips, sawdust, compost, composted sewage sludge, etc.

Inorganic mulches provide a long-term ground cover. A weed-control mat should be placed below the mulch. Use a mat that allows water to penetrate. Marble chips, river gravel and crushed brick are popular inorganic mulches.

Weed control is important for water conservation. Weeds will compete with desired plants for water and nutrients. A 2-inch layer of mulch is the best defense against weeds. Other methods of weed control in the home landscape include hand pulling, mechanical cultivation and the selective use of herbicides.

Many plants require more nutrients than can be obtained from the native soil. Nutrients are added in the form of fertilizers. Most fertilizers include nitrogen, phosphorus and potassium. it is best to fertilize perennial plants (trees, shrubs and lawns) in the fall.

The addition of fertilizer (especially nitrogen) will encourage new growth. In the spring, plants put the extra nutrients into increased top growth. New growth is undesirable just before a period of drought stress. In the fall, most plants put extra nutrients into root growth, which increases the plant's ability to locate and take up water.


  • Use mulches to conserve soil moisture.
  • Rake organic mulches to prevent crust formation.
  • Under inorganic mulches, use a weed control mat that allows water percolation.
  • Control weeds that compete with desirable plants for water.
  • Fertilize perennial plants in the fall.

Water Requirements

Shade trees:

  • Newly planted - water once per week
  • Established - water twice a month in summer and fall



  • Newly planted - water weekly, especially into fall and winter
  • Established - water twice a month all year


  • Newly planted - water twice per week
  • Established 3-5 years old - water weekly during the growing season and twice a month in fall and spring


  • Newly planted - water three times per week
  • Established - water weekly during the growing season


  • After planting seed - water every other day until seedlings emerge
  • Established - water once a week during the growing season

Watering Methods

Deep soakings that wet the soil to a depth of 5 to 6 inches are the most efficient way to water. To determine the depth that is wet, probe the soil with a screwdriver or a probe that removes a soil plug.

If water is applied faster than the percolation rate of the soil, runoff will occur. In that case, water until runoff, allow the water to soak in and water again one hour later. Continue until the soil is wet to a depth of 5 to 6 inches.

It is best to water in the early morning or late afternoon when it is cool and less windy. Loss of water to evaporation will be less.

If at all possible, avoid overhead sprinklers. Overhead sprinklers are 75 percent efficient whereas drip or subsurface irrigation is 90 percent efficient. Use an open hose at the base of small or newly planted shrubs and trees. For larger trees, spread a soaker hose over an area under the tree about as wide as the tree is tall. Put hoses on timers to avoid waste. Drip or subsurface irrigation systems are the most efficient ways to water landscape plants. If you must use overhead sprinklers, never use them on windy days and locate them so you avoid watering sidewalks and driveways.

  • Water with deep soakings that wet the soil to a depth of 5 to 6 inches.
  • Water in the early morning or late afternoon.
  • Avoid overhead sprinklers.
  • Put hoses on timers.

You can make a difference. Please do your part to help conserve water and keep our landscape growing.

Credits: EPA, DNREC, New Castle-Kent-Sussex Conservation Districts, Delaware Nature Society, Delaware Cooperative Extension, University of Delaware.

Write to the New Castle County Cooperative Extension office, University of Delaware, 910 S. Chapel St. Newark, DE 19717-1303 for a copy of any publication you need.


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