Landscape Irrigation is a term to describe the artificial application of water to a landscape. To keep your gardens thriving requires the careful management of irrigation practices. The following tips will help.
Landscape Irrigation Timing
Studies have indicated that plants utilize root zone water most efficiently during morning hours…try to irrigate very early in the day. Much of the water applied during the heat of the day is lost to evaporation – thirty percent or more is lost from overhead irrigation. Watering during evening or nighttime hours may be acceptable, but plants which are susceptible to fungus diseases will suffer from being damp for the extended overnight period.
The general rule is to water as deeply and as infrequently as possible. Watering deeply and infrequently encourages the plant to develop a deep root system, which in turn increases drought hardiness, since the soil dries from the top down. Frequent, light irrigation encourages a shallow root system which will suffer from every dry spell.
Landscape Irrigation for your Soil Type
Many folks have asked how much, or how long to irrigate…this depends on the soil – and the crop. In an “average” loam, one inch of irrigation will penetrate twelve inches…in a sandy soil, penetration will be deeper, and in a clay soil, not as deep. For established shrubs in the average loam, a thorough, deep irrigation once per week to the depth of one and one half to two feet should be adequate during the growing season. Since clay soils hold water longer, care must be taken to not over water, which will exclude necessary oxygen from the soil profile.
(The “ideal” soil is composed of fifty percent solids, twenty five percent liquid and twenty five percent air).
Landscape Irrigation for your specific plants
Plants have different water needs…for instance, the red-twig dogwood (Cornus stolonifera) will thrive in a soil that is always damp – but many other plants require a thorough drying between irrigations – so if at all possible, group plants of similar water needs together. The website review below refers to an excellent article about designing for efficient water use.
Landscape Irrigation for your Lawns
For lawns, there is no substitute for overhead irrigation. For shrub beds, vegetable and herb gardens and fruit trees, drip irrigation is far superior – the plants receive a slow, metered supply of water, which is not as susceptible to losses from evaporation and overspray. For row crops in the vegetable garden, I’ve been using “porous pipe,” made from recycled rubber, with great success.
For several years I have been encouraging my design clients to use drip irrigation for their planting beds. Recurring drought in many parts of the country has made us reconsider how we use one of our planet’s most valuable resources. The following is a brief introduction to the basic principles and advantages of drip systems.
The term “drip irrigation” describes the application of water not only by drip emitters but also by microsprays. Both of these have two traits in common: they operate at low pressure, and they deliver a low volume of water compared to standard sprinklers.
Because the water is applied slowly on or near the ground, there should be no waste from runoff and little or no loss to evaporation. You position the emitters to deliver water just where the plants need it; you control penetration by varying the time the system runs and/or the emitters’ delivery capacity (rated in gallons per hour).
You can also regulate the volume of water delivered to each plant by varying the type and number of emitters you set up for each.
Besides water conservation, the chief advantage of drip systems is flexibility. You can tailor the system to water individual plants by providing each with its own emitter(s); or you can distribute water over larger areas with microsprays.
A standard layout might include hookups to two or more valves and many kinds of parts. Because the lines are above ground (they’re easily concealed with mulch) and are made of flexible materials, changing the system is simple: just add or subtract lines and emitters as needed.
Your drip system can be simply attached to a hose end or screwed into a hose bibb. Or, if you prefer, you can connect it permanently to your main water source.
Drip irrigation is perfect for the driest zones of a landscape. A drip system saves water because very little is lost to evaporation or runoff.
By delivering water slowly and directly to a plant’s root zone, drip irrigation promotes healthy plant growth. Water savings can easily be 50% or more versus traditional sprinkling. Drip emitters are well-suited for most xeric trees, shrubs and perennials.
Landscape Irrigation Delivery
Keep in mind that sprinklers and drip emitters apply water at different rates (measured in gallons per minute and gallons per hour, respectively). It’s best to put sprinklers and drip emitters on different irrigation valves. Also, a drip system requires a pressure regulator to limit pressure to the system and a filter to insure that the tiny emitter openings do not clog.
UPDATE: We have converted all of our ornamental beds to in-line drip tubing manufactured by Netafim.
As with most topics relating to the garden and landscape, irrigation solutions are dependent on site specific conditions – you must know your soil and your plant needs to make the best irrigation decisions.
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About Dan Eskelson
Dan has had his hands in the soil for most of his adult life as a gardener, landscaping contractor, golf course superintendent and landscape designer. When the ground freezes, he builds websites, produces video and plays the hammered dulcimer. Full bio here.