Watering Landscape Plants

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Landscape Design, Construction, and Maintenance

Instructional Materials Service

Texas A&M University

Today We Will…

Discuss the functions of water in plant growth and development.

Explain the effects watering has on landscape plants.

Describe how to determine when landscape plants need watering.

Discuss methods of watering landscape plants.

Today We Will…

Explain how to determine the quantity of water to apply to landscape plants.

Discuss the importance of water quality considerations.

Explain how to determine the time and frequency for watering landscape plants.

Describe effective and efficient watering practices used in watering landscape plants.

Functions of Water in Plant Growth and Development

Provides essential nutrients. Major component of plant cell. Solvent and medium for chemical reactions

and processes Maintains turgidity. Medium for transporting nutrients and food. Component of photosynthesis. Assists in the movement of plant parts Maintains stable temperature within plant.

Water and Turgidity

Water is important for keeping plants and their cells turgid. Turgidity is a plant state in which the plant is

rigid and inflated with water. Plants may appear wilted due to a lack of

turgor pressure. Turgor pressure is the pressure inside a cell

due to water uptake.

Water and Turgidity

Water and Temperature Stability

Water serves as a buffer within the plant against sudden changes in the exterior environment. In cold temperatures, water maintains plant

energy and uses it to moderate the temperature of the plant.

In warm temperatures, water releases heat to cool the plant.

Water Functioning in Soil

As they absorb water from the soil, plant roots also absorb minerals that have been dissolved in the soil water.

Plants lose a great deal of water due to transpiration and replace this lost water with moisture from the soil. Transpiration - plant releases water from its

leaf surfaces in the form of water vapor

Water Functioning in Soil

Leaching occurs when nutrients are washed past the root region and become unavailable to plants.

Water applied to the soil helps leach out excessive levels of minerals in the soil near the plant’s roots.

Water and Landscape Plants

Landscape plants require adequate water to survive.

The amount of water a plant receives affects its growth and development.

Both under-watering and over-watering impact plant growth and development.

Determine whether plants need to be watered by observing them for signals or by checking the soil for moisture.

Effects of Under-Watering

Reduced growth rate. Reduced rate of photosynthesis. Wilting due to decreased turgor pressure

when plant transpires faster than roots can supply lost water.

Eventual death due to lack of water and permanent wilting.

Effects of Over-Watering Taller growth with less compactness. Shallow root system. Nutrient deficiencies due to leaching and

shallow root system. Plant roots may “drown”

Signals that Turfgrass Needs Water

Wilting in which leaves bend or roll up. Overall dull, grayish appearance. Leaves appear dull with a bluish-green

to purplish cast. Grass lies flat after being walked on. Intrusion of weeds.

Signals that Trees, Shrubs, and Groundcovers Need Water

Discoloration in which leaves go from glossy, bright-green to dull, gray-green.

Wilting. Premature leaf, bud, and flower drop. Death of young leaves.

Watering Needs of Container Plants & Transplants

A high potential for drought stress occurs in container plants because moisture from the surrounding soil does not move into the container soil mix and root zone quick enough to prevent drought stress.

Frequent watering is necessary until the root systems of transplanted plants spread and develop into the soil of the new location.

Checking Soil For Moisture

Cane or Stick Insertion Insert a cane or stick into the soil around the

root system. If it has no moisture or soil clinging to it when

removed, water is needed. Moisture or soil clinging to it indicates

adequate moisture.

Observing the Soil Soil appearing light in color and dry to the

touch indicates a need for watering.

Checking Soil for Moisture

Feeling the Soil Roll or squeeze a small

bit of soil into a ball. A soil ball that crumbles

when rubbed has proper moisture.

If the soil ball does not crumble when rubbed, it is too wet.

Water is needed if soil will not form into a ball.

Sandy soils crumble even when wet.

Photo Courtesy of USDA Natural Resources Conservation Service

Methods of Watering Landscape Plants

Sprinkler Irrigation Drip Irrigation Surface Irrigation Manual Irrigation

Sprinkler Irrigation Most commonly used method of irrigation. Effective and efficient method of evenly

distributing water over a lawn area. Applies large volumes of water in a short

time. Requires minimal maintenance. Includes hose-end sprinklers and

automatic underground pop-up sprinkler systems.

Types of Hose-End Sprinkler Systems

Oscillating Sprinklers Spray Type Sprinklers Impact Sprinklers

Oscillating Sprinklers Provide an even supply of

water back and forth across an area.

Maintain an even watering pattern throughout lawn area.

Should be moved frequently and evenly throughout the area.

Should overlap about half of each pattern when moved.

Spray Type Sprinklers

Distribute water to an area either with a fixed spray or rotary spray.

Provide a constant, uniform supply of water to an area.

Impact Type Sprinklers Shoot a fine spray of water

across an area. Impact of water passing

through the sprinkler nozzle changes the direction of the stream in short movements around the sprinkler.

Those on risers of about 2 to 3 feet sprinkle water above shrubs, providing a more equal distribution of water.

Photo Courtesy of USDA Natural Resources Conservation Service

Selecting a Hose-End Sprinkler

Choose one that sprays large water drops, close to the ground.

Avoid sprinklers that produce fine streams of water high into the air.

Automatic Underground Pop-Up Sprinkler Systems

Consists of the following components:

Underground distribution lines. Electrically controlled valves. Electric program controller. Pop-up sprinkler heads.

Automatic Underground Pop-Up Sprinkler Systems

Advantages More water efficient

than hose-end sprinklers.

Sprays water near the ground and closer to the roots of plants.

Allows for dividing areas into zones that can be watered separately, according to specific needs.

Disadvantages Expensive to

install. Nozzles may

require cleaning if clogged.

Heads and nozzles may have be adjusted to ensure walks and drives aren’t watered and large drops rather than a fine spray is emitted.

Drip Irrigation Systems

Involves the following components:

Supply tubes Thin connecting tubes Emitters

Photo Courtesy of USDA Natural Resources Conservation Service

Advantages of Drip Irrigation Systems

Efficient Economical Improved Plant Health

Disadvantages of Drip Irrigation Systems

High cost of materials and instillation. Emitters may occasionally become

clogged.

Guidelines for Use of Drip Irrigation Systems

Operate system for at least three hours to achieve thorough soaking.

Bury supply tubes and thin tubing, or cover them with mulch.

Surface Irrigation

Involves flooding or allowing water to cover an area.

Commonly used in landscape for watering flowerbeds.

Also used in landscape for close plantings of trees or shrubs.

Surface Irrigation

Advantages Provides good,

uniform wetting of the soil in the irrigated area.

Disadvantages Uses a great deal

of water. Requires a level

surface, or runoff becomes a problem.

Guidelines for Surface Irrigation

Construct small berm around area to be watered.

The berm creates a small basin to retain water and to prevent surface runoff.

Allow water to cover the soil surface to a depth of 1 to 2 inches.

Berm

Manual Irrigation

Involves watering landscape plants by hand.

Supplies water to plants by means of a hose or bucket.

Manual Irrigation

Advantages Allows each plant

to be personally monitored by the irrigator.

Disadvantages Requires a great

deal of time. Requires a lot of

labor. Requires a lot of

water.

Using a Hose for Manual Irrigation Make sure hose

reaches all plants to be watered.

Attach a water breaker to end of the hose.

Using a Bucket for Manual Irrigation

Apply water slowly. Do not pour all water

at once. Apply water close to

the soil surface.

General Guidelines for Manual Irrigation

Fill the basin surrounding the base of the plant.

Allow water to infiltrate down into the soil in the plant’s root zone.

Do not allow excessive water runoff.

If no basin exists, apply water away from the trunk or stem to the canopy drip-line. Drip-Line

Factors to Consider in Selecting An Effective Irrigation Method

Size and topography of area

Type of plants Labor

requirements (time and cost)

Uniformity of application

Quality, quantity, and availability of water

Cost of installation Life expectancy of

system Economics of

operation

Determining Quantity & Frequency of Watering for Landscape Plants

Watering needs differ among landscape plants. Factors to consider in determining how much

water to apply to plants include: Plant Species Plant Size Plant Age Stage of Plant Development Soil Texture Slope of Land Environmental Conditions

Guidelines for Determining Quantity of Water to Apply

Apply enough water to thoroughly soak the soil surrounding the plants’ roots.

Apply water at a slow enough rate to prevent runoff.

Apply water regularly to newly planted landscape plants.

Guidelines for Determining Quantity of Water to Apply

Satisfy the water requirements of established plants.

Avoid applying too much water. Consider water received in the form of

rainfall. Consider the placement of plants.

Determining the Effectiveness of Landscape Watering

1. Water an area for 15 minutes.

2. Dig to find the depth of moisture penetration.

3. Calculate the time needed to thoroughly soak plants based on the depth of moisture penetration.

Thoroughly wetting the root zone of an established large shrub or small tree may require 6 to 12 hours.

Determining Water Quantity Received by Lawn Area

1. Set several wide-topped, flat-bottomed cans with straight sides in a straight line out from sprinkler.

2. Check the water level in the cans at 15- minute intervals.

3. Adjust the sprinkler’s rate of application to about ½ to 1 inch per hour.

Determining Water Quantity Received by Lawn Area

Time for Watering Landscape Plants

Water during the early morning hours. Calm winds and a cooler temperature reduce

water lost to evaporation and ensure a uniform watering pattern.

Discourages development of disease-causing pathogens because foliage dries in a short time.

Tips for Effective and Efficient Watering

Water plants only when they need it and apply only enough to satisfy their needs.

Water plants thoroughly to reduce the amount of water and frequency of watering.

Mulch landscape plants to keep soil cool and to reduce water lost to evaporation.

Add organic matter to increase drainage in clay soils and to retain moisture in sandy soils.

Tips for Effective and Efficient Watering

Avoid watering weeded or unplanted areas.

Taper off watering during late summer and early autumn to encourage plants to harden and become tolerant to cold winter conditions.

Water plants periodically during the winter to supply water to plant roots as they continue to grow.

Things to Remember About Effective and Efficient Watering

The greatest waste of water is due to applying too much, too often.

Be observant in hot and dry summer weather when plants never absorb and use much of the water applied. As much as 50% of water is wasted through

runoff and evaporation.

Water Quality Considerations

Use irrigation water that is free of suspended matter or particles.

Avoid using water with high salinity level Chlorine and fluoride added to city water

for health reasons usually isn’t present in high enough levels to affect landscape plants.

Water Quality Considerations

Water quality varies from one location to another.

In some cases, mineral content is so high that it affects plant growth.

Have water tested if problems occur.

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presentation without written permission is prohibited.

Instructional Materials Service

Texas A&M University

2588 TAMUS

College Station, Texas 77843-2588

http://www-ims.tamu.edu

2007