Taking an early morning walk one day this week we walked past a geyser. In a nicely tended, water-efficient landscape planting, water was spouting about 20 feet in the air and out onto the street. It looked hilarious, but it is a sad waste of water.
Last week, I saw a less conspicuous one: a section of drip irrigation “spaghetti” tubing, squirting a stream of water aimlessly onto some bark mulch. The drip emitter had fallen off and the owner was, apparently, unaware of it.
Those are examples of only one of the dangers of automatic irrigation systems when we set them and forget them. Various problems ensue:
— The settings are often based on a “guesstimate” of the water needs of the plants, but the root zones don’t get checked to verify effectiveness.
— Drip emitters are placed on top of the root ball, as needed for new transplants, but not relocated as the root systems grow larger.
— Timer settings are commonly turned off for the winter, which can lead to drought damage in a dry winter, and set to run for a single, set duration and frequency from spring, summer and fall even though water needs vary through the seasons.
Focusing on young trees, irrigation mistakes cause more damage than any pests or diseases do. And irrigation mistakes often predispose plants to pest and disease problems.
The time and effort are at the heart of this problem. To get a reality check, it requires periodically monitoring the system while it is running, and the use of a probe or a moisture meter or soil sensors to verify soaking and drainage between cycles.
With respect to new transplants, it is common for the root ball to dry out while there is plenty, or too much moisture under and beside it. When all of the roots are still in the ball a transplanted tree can become drought stressed even though it is surrounded by moist soil.
Further problems come from the root ball sitting in a puddle at the bottom of the planting hole. Roots suffocate in standing water and water mold diseases thrive, infecting and killing roots.
Working with smaller numbers of trees, I prefer monitoring by getting a small sample of the soil and feeling it to evaluate the moisture content.
Lately, I have enjoyed using the ePlanter SPROBE-20 for this purpose. It is a simple aluminum 20-inch spike bent into a loop at the top with flat grooves at intervals along the shaft. It captures small bits of soil at several depths.
(See it online at: www.eplanters.com/soil-probe.html)
Here are the steps I like to use to make informed decisions on scheduling:
1. At planting time, use a garden hose to thoroughly soak the planted root ball. Wait a day or two, then use a probe to check for moisture inside the transplanted root ball, under it and beside it.
A simple way to judge the amount of moisture is to form the soil sample into a clump. If it does not hold together it is too dry. If it holds together it is probably moist enough to foster root growth. If it is shiny or dripping wet, it is too wet.
2. If you are using an automatic irrigation system, “guesstimate” the volume of water and the frequency needed to water and maintain the newly planted tree.
3. Place drip emitters directly on top of the root ball.
4. After the first irrigation cycle, probe to verify soaking of the root ball.
5. Before the cycle repeats, probe to verify complete drainage of the hole and partial drying of the root ball. Adjust duration and frequency as needed.
6. Repeat step 5 before the cycle repeats.
7. Repeat step 5 seasonally. Adjust as needed for the time of year.
8. Once the tree is rooted- about two to six months after planting — revise the irrigation layout to water the surrounding garden soil and allow the nursery root ball to dry out.
The idea here is to help the tree generate a large root system and to avoid chronic wetness at the root collar — the base of the tree.
9. Make it a habit to periodically run each station on the irrigation timer and go out and look for malfunctions.