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Clues to Other Directions in Irrigation

Survival of Unirrigated or Sporadically Irrigated Plants
On our restoration projects, we install solid and reliable irrigation systems that water the plants once or twice per week. We need to, because we must guarantee a minimum level of survival of the plants while the area is under our maintenance and responsibility. However, when I install trees on remote areas of our property, I don’t install irrigation systems. I install the plants in the spring and I intend to water them regularly during the summer, but rarely if ever get around to it. The cobbler’s children go barefoot. However, I’ve noticed that almost all plants survive until late July or early August, going three or four months without irrigation. They only start to die off during heat waves in the late summer and fall. If I give the plants one deep watering, or better, two deep waterings a month apart, they usually survive the summer drought in good shape.

A plant in the right place can survive the summer drought with deep, but highly infrequent waterings, or possibly no watering at all. Plants that have survived this level of stress are more likely to survive on their own than those that have received frequent irrigation.


Natural Recruitment
We seem to forget this, but plants reseed themselves naturally without irrigation or other aid. We only notice it for weeds and noxious plants, but it happens all the time. Native grass seeding projects are performed successfully without irrigation. Nature does not rely on artificial irrigation systems.

It is worthwhile to observe the conditions under which seeds germinate and grow. The most important advance in restoration will come when we understand the seedbed and how to foster natural recruitment of natives while discouraging the recruitment of weeds. Container plant installation will be reserved for small spot treatments, but seedbed control will be the method for treating large acreage.

Whether you are using seeding or container plant installation, the same rule holds: you want the new plant to grow in a location where it will thrive without supplemental aid.

Dri-water is essentially a small container of gel, consisting of water and corn starch. It comes in small cartons or in plastic sausage casings, roughly one quart in size. You cut open the bottom and place one or two in the ground near the roots of a newly installed plant. The gel slowly decomposes and releases the water. You replace the dri-water every month or two. I did not expect it to work. However, we used it on a project, and found that it resulted in improved survival. The plants did not grow quickly or vigorously, but they did survive in higher numbers than I would have expected without the dri-water.

We still don’t use it very much, but only because of the labor expense of carrying boxes of water to individual plants. However, the theory appears to work.

A little bit of water goes a long way.

The take away message is that consistent, abundant watering is not necessary for a plant to survive in the wild, assuming it is properly installed in the right soil and site conditions. A little bit of water is all that is required. A plant can survive months without irrigation if there is enough residual moisture in the soil. Irrigation should provide just enough water to enable the plants to survive the summer drought. Up to a point, drought stress is beneficial.

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