Some plants are composed of up to 95 percent water. Water is vital from the moment seeds are sown through sprouting to the end of the growing season. Plants need water for cell division, cell enlargement, and even for holding themselves up. If the cells don't have enough water in them, the result is a wilted plant. Water is essential, along with light and carbon dioxide, for producing the sugars that provide the plant with energy for growth. It also dissolves fertilizers and carries nutrients to the different parts of the plant.

Watering, whether for rows of crops or in containers, is often necessary to supplement rainfall.
Watering, whether for rows of
crops or in containers, is often
necessary to supplement
rainfall. See more pictures of
vegetable gardens.

Ideally, water for plants comes from rain or other precipitation and from underground sources. In reality, you'll often have to do extra watering by hand or through an irrigation system. How often you should water depends on how often it rains, how long your soil retains moisture, and how fast water evaporates in your climate. Soil type is another important factor. Clay soils hold water very well -- sometimes too well. Sandy soils are like a sieve, letting the water run right through. Both kinds of soil can be improved with the addition of organic matter. Organic matter gives clay soils lightness and air; it gives sandy soils something to hold the water.

Other factors may also affect how often you need to water your garden:
  • More water evaporates when the temperature is high than when it's low. Plants can rot if they get too much water in cool weather.

  • More water evaporates when the relative humidity is low.

  • Plants need more water when the days are bright.

  • Wind and air movement will increase the loss of water to the atmosphere.

  • Water needs vary with the type and maturity of the plant. Some vegetables are tolerant of low soil moisture.

  • Sometimes water is not what a wilting plant needs. When plants are growing fast, the leaves sometimes get ahead of the roots' ability to provide them with water. If the day is hot and the plants wilt in the afternoon, don't worry about them; they will regain their balance overnight. But if plants are wilting early in the morning, water them immediately.
So much depends on climate and the ability of different soil types to hold moisture that it's difficult to give specific directions for watering your garden. Generally, however, vegetable plants need about an inch of water a week. The best time to water your garden is in the morning. If you water at night when the day is cooling off, the water is likely to stay on the foliage, increasing the danger of disease. Some people believe that you shouldn't water in the morning because water spots on leaves will cause leaf-burn when the sun gets hot; this isn't the case.

When watering your vegetable garden, there is one rule you should follow: Always soak the soil thoroughly. A light sprinkling can often do more harm than no water at all: It stimulates the roots to come to the surface, where they are killed by exposure to the sun.

To learn about irrigating your vegetable garden, go to the next page.

Want more information about vegetable gardens? Visit these links:
  • Caring for a Vegetable Garden: Read our guide to nurturing your vegetable plants for the best harvest.
  • Vegetable Gardens: Find out everything you wanted to know about vegetable gardening.
  • Vegetables: Pick out your favorite vegetables to plant in next year's garden.
  • Gardening: We answer all of your general gardening questions in this section.
  • Garden Care: Whether you're growing cucumbers or columbines, we have all the information you need to nurture a thriving garden.