Save Water by Learning How Much Your Plants Really Need

The following is an excerpt from Solar Gardening: Growing Vegetables Year-Round the American Intensive Way by Leandre Poisson and Gretchen Vogel Poisson. It has been adapted for the Web.

Mention watering, and the first thing we think of is how we can garden so that we don’t have to water. If a garden’s soil is rich with humus, the decomposing organic matter will absorb water like a sponge and hold in the moisture, making it available to growing plants. Mulching also makes for moist soil, because it prevents the evaporation of water from the ground’s surface. That’s why, in American Intensive Gardening, we grow plants close together to form a living mulch. Just like a miniature rainforest, the canopy of leaves shades the soil, keeping it cooler and reducing moisture loss through evaporation.

Recently we came across some old gardening notes that indicated that in 1978 we had had to water our garden for the first time in its nine-year history. In fact, until the past few years watering has never been a consistent part of our gardening activities. We might have watered seedbeds or seedlings, but we rarely found it necessary to provide additional water for growing plants. But our climate seems to have changed so much in recent years that we now begin watering in May and continue through the course of the summer. In addition, the lack of snow cover in our area over the past few winters has given us spring seasons with little surface moisture. This new need to water has helped us empathize with gardeners who live in arid regions of the country. We have learned, much to our dismay, just how time-consuming watering a garden can be.

Transplants and newly seeded areas most always require some watering. Growing plants need consistent moisture, no extremes of too-wet or too dry conditions. By observing your garden closely, it should be clear to you when you have to water. If leaves begin to wilt, if broccoli and cauliflower plants form buds while they are still immature, or if the soil feels and looks dry more than an inch below the surface, the garden wants either watering or a good soaking rain very soon.

Observing the weather can also provide important clues as to when you should water. In our area, if we receive anywhere from one-half to one inch of rain during the week, we generally don’t need to water. An un-mulched garden, though, or one that has a sandy, fast-draining subsoil might demand supplementary watering, even with adequate weekly rainfall.

Different gardeners will develop their own favorite systems for watering, based on the equipment available to them and how frequently they need to water to keep the subsurface soil moist. There are, however, some general guidelines for when and how to water. In humid areas of the country, the best time to water is early in the morning, to allow the surface soil to dry out during the day and discourage fungus problems. In arid regions evening watering is preferable to decrease the amount of evaporation. With soil whose structure is predominantly clay, water will take a long time to penetrate, so a slow-drip system of irrigation in this case is a good option. With sandy soils you can use a more rapid delivery system, though you still need to water more frequently than on clay soils.

We prefer delivering water to the surface of the soil rather than wetting the leaves of the plants. A powerful spray of water may disturb tender seedlings, and the sun can burn and damage wetted foliage. For irrigating our plants, we like to use the so-called soaker hoses made from recycled materials, which are available from most garden supply stores. We also own a few drip irrigation hoses. If we do water with a regular garden hose, we use a wand attachment and move it around the base of the plants. For applying solutions of liquid fish emulsion fertilizer or manure tea (see page 104 for our recipe), we recommend using a metal watering can and irrigating around the base of the plants.