Irrigation-A Key to Plant Success

by Ken Muellers

Ken Muellers is a designer at The Laurel Group and is an ISA Board Certified Master Arborist and can be contacted at   

Ken Muellers is a designer at The Laurel Group and is an ISA Board Certified Master Arborist and can be contacted at


In our region, we average a little over 40 inches of rainfall a year. In theory, this is enough water for most established plants to live. I say, “in theory” because of a couple key caveats. One is that the rainfall comes when the plants need it, which it often doesn’t. The other is the pesky word “established.” When plants are newly installed, they often have a very limited root system which can take in only a fraction of the water an established plant can. That is why proper watering is so critical in a new landscape. And the best way to ensure plants receive adequate water is an automatic inground irrigation system.

Irrigation systems are typically made up of three main components, the controller or clock that acts as the brain of the system, the lines and manifold that distribute the water throughout the landscape and the various emitters or heads that release the water to the plants.

Since water pressure is usually not sufficient to water the entire yard at once, systems are divided into different zones for coverage. This allows for each portion of the landscape to be watered for a designated amount of time programed into the controller. A good system will separate lawn areas from planting beds, as these two have different watering requirements. The water can be emitted though rotary heads (the ones that turn around) usually used for lawn areas, mist heads that are often used for plant beds or driplines, which are ideal for hedges. A drip system uses tubing with emitters spaced along its length allowing a slow trickle of water to be released at the roots of the plants. This is the most efficient way to water since very little is lost to evaporation as with mist or rotary heads. The disadvantage to a drip system is that you cannot see what is getting water and what is not, so you do not usually know there is a problem until you have dead plants on your hands.

With any system, it is important to monitor and adjust for the time of year and natural rainfall. The running time on each zone can be increased or decreased depending on the need. Most systems incorporate a rain sensor that prevents the system from running after a substantial rainfall. But seasonal adjustments need to be made manually to up the watering times during warm, dry periods and reduce watering in cooler, wetter times. As a landscape becomes established over the first couple years, less and less supplemental water will be needed, and the system should be adjusted accordingly. When the plants are established, it is better to do a deep watering once or twice a week, rather than short, frequent watering. This deep watering promotes root development to reach deeper for moisture and, thus, make the plant more drought resistant.

With the cold winters in our region, it is important to have an in-ground system winterized to prevent the pipes and heads from being damaged by frozen water left in the lines. This is done by using compressed air to blow the water out of the system at the end of the season.

Look at that, I got through a whole article without any jokes about how irrigation isn’t a dry topic; well almost the whole