How and When to Water

Gardeners can’t depend on Mother Nature to do all the watering, all the time. That’s why watering your garden wisely (and conserving moisture once it gets in the soil) is a fundamental skill that your crops will thank you for cultivating.

What Type Is Your Soil?

How well your garden soil retains the water it receives depends on what type of soil you have. To keep things simple, we’ll classify soils into three general types: sand, loam, and clay.

Sandy soils have lots of air spaces between the particles. This allows for good drainage—sometimes too good. Water moves through sandy soil fast, and the soil tends to dry out rapidly.

Clay soils are just the opposite. They have almost no air spaces between particles and drain very poorly. Clay absorbs water slowly but once wet, holds lots of water (often too much).

Loam is the middle ground between sand and clay. It absorbs water well and dries out at a nice moderate rate.

But no matter what type of soil you have, the key to keeping water in your garden is compost, compost, compost. Compost helps improve any soil by acting like a moisture-retaining wick. Every shovelful of that rich organic matter you add to the garden boosts your soil’s ability to hold water.

Keep in mind that you’ll have to apply more—not less—water to a garden high in organic matter to wet the soil to the depth you want. But because the soil holds more water, your garden may be able to go longer between waterings.

How to Watch for Water Stress

When plants are chronically underwatered, they experience water stress—a more serious situation than simply wilting a bit during the heat of the day. A plant that gets a little too hot usually recovers when the day cools off, but plants still drooping in the morning or late evening need water fast! (Some waxy-leaved plants like cabbage, onions, and garlic don’t show water stress as readily as plants like peas, lettuce, and spinach do, so water them very carefully for signs of water stress.)

Water-stressed plants can have leaves that are smaller than normal. The edges of those leaves may turn brown, and the flowers and fruits will be delayed or drop from the plant. Water stress also reduces the quality of the produce—for example, your cucumbers may be small and misshapen; tomatoes may develop blossom-end rot; and salad crops and celery may have tough fibers. (Note: Water-logged soil causes plants to exhibit many of the same symptoms.)

When Water Is Critical

Moist soil is essential for seed germination and seedling growth. Try to set your young transplants in the garden on cloudy days or in the evening. And always water your seedlings when you set them out.

Once plants pass the seedling stage, essential watering times vary from crop to crop. Sweet corn needs an abundant supply when the silks and tassels are forming. Tomatoes, cucumbers, and squash are especially thirsty when they’re flowering and when their fruit starts developing.

On the other hand, there are times when it’s necessary to cut back on watering. Most muskmelons will taste better and have better quality if you start to cut back on water 7 to 10 days before harvest. And onions cure faster and store better if you hold off the water after they reach maximum bulb size and about half the leaves have fallen over. For pumpkins and winter squash, you want to dry the vine up before harvesting.

One thing to remember if you have to ration water: Certain plants can take drought better than others. Deeply rooted melons are somewhat tolerant to such stress, as are asparagus and beets. Tomatoes and brassicas are semitolerant. But don’t deny a drink to sensitive celery, strawberries, lettuce (especially head lettuce), cucumbers, squash, and peppers.

When to Water

Water in the morning or in the evening, but never during the heat of the day, during which time you waste the water because it evaporates quickly.

Water in the morning if you garden in a humid climate or are watering plants that are prone to foliage diseases. If you water in the evening, the soil and the plants will stay wet most of the night, promoting disease and fungal growth. This is especially important if you use overhead watering (like a sprinkler), which sprays water right on the plant.

Water at night if (1) you have no disease problems in the garden; (2) you live in an arid climate; or (3) you use a drip-irrigation system that waters the soil, not the plant leaves.

How Often and How Much

The best guideline is to water your garden when about half the available water in the soil is depleted. (Don’t wait until a lot less is available; big fluctuations between wet and dry harm plants.) To figure out when that is, dig down 4 to 12 inches and feel the soil. Squeeze a handful of soil into a ball and see what happens.

If you have sandy soil, your sample should stick together slightly or form a weak ball under pressure. If it doesn’t, you need to water.

For loamy soils, your sample should form a loose ball under pressure. If the soil looks dry and won’t form a ball, it’s time to water.

Clay soil should form a ball easily and ribbon out between your thumb and forefinger when you squeeze it. If you have to apply even a little pressure to form a ball, your garden needs some water.

But how much water should you apply? Always wet the soil at least 1 foot deep. Otherwise, plant roots will stay in the top 4 inches of soil, causing plants to be more vulnerable to water stress. Deep watering encourages deep roots, which allow plants to better withstand drought.

One last factor: How should you apply water? Drip irrigation? A sprinkler? Your choice affects how much water you need to put on the garden. Drip irrigation is more efficient—about 85 percent of the water goes directly to the plants’ root zone; overhead watering is about 70 percent efficient. Be sure to add more water to compensate for these inefficiencies. And no matter how you apply the water, remember to water slowly to minimize runoff.

Other Water-Wise Tips

Conserving water can be just as important as adding water to your garden especially during dry spells. Here are some hints to help ensure your garden loses as little water as possible.

Mulch, mulch, and mulch some more.
Mulching can save almost one-third of the water you put on your garden, according to researchers. Mulch will also help keep soil cooler and protect tender roots. And it will keep down your biggest competitor for garden moisture—weeds.Apply up to 3 inches of compost, wood chips, grass clippings, or any other organic mulch. (If you mulch on top of a drip-irrigation system, you may have to cut back on the amount of water you apply because mulch makes drip irrigation superefficient.) Just don’t use plastic mulch with overhead sprinklers—the water won’t get through to the soil.
Plan ahead to conserve water.
First, try to do as much of your planting as early as possible in the spring and late in the fall. In these cooler times of year, a minimal amount of water is needed to get plants going strong (and strong plants are better able to tolerate droughts later on). Be aware, however, that cool-season crops generally have shallow root systems and require more frequent watering.
Garden in raised beds.
The deeply loosened soil in a raised bed absorbs water better than the soil in a standard garden will.
Space plants closely.
Reducing spaces between plants in beds and between rows will make mature plants into a living mulch—much of the soil will be shaded by their leaves.
Group crops that have similar water needs.
Plant your heavy water users, such as beets and broccoli at one end of the garden, light users like beans and squash at the other. Then water the two areas separately.
Cut down on cultivation.
Working your soil quickly dries out the upper few inches. Instead of hoeing to keep down weeds, smother them with moisture-conserving mulch.