Watering Your Vegetables

Watering your vegetable garden seems simple enough: if it’s dry, water it. But how much water is enough - and how much is too much? What time of day is best to water? When are the critical times to water to ensure a successful crop?

How Much Water Does My Garden Need?

The rule of thumb is to make sure your garden gets at least 2.5 cm (1 inch) of water weekly. Use a rain gauge, a tin can, or other straight-sided container in the garden to keep track of rainfall and provide additional water as needed.

Some crops can get by on less than 2.5 cm of water per week, but this is a good general guideline. Aside from rainfall, many other factors come into play when determining how much water is needed. If it’s cloudy, you can reduce watering, as there’s less evaporation. When it’s hot and dry, you’ll need to water more.

Soil type also affects watering needs. Clay retains water well, while sandy soil retains it poorly. A good loam is well-balanced to hold moisture while providing adequate drainage. With clay soils, water takes longer to seep in, so slow watering is required to avoid forming puddles. Clay soil may become waterlogged. With sandy soil, water drains though quickly, so more frequent watering is required.

Once you’ve got the minimum watering needs of your garden taken care of, consider the needs of individual vegetables. According to Cornell University researchers, in good garden loam, 2.5 cm of water will penetrate to a depth of 38 cm (15 inches). This is fine for brassicas, sweet corn, lettuce, potatoes, radishes and spinach, which need to be watered to a depth of about 30 cm (12 inches). Some crops need more water, however, for optimal growth. Beans, beetroot, carrots, cucumbers, peas, peppers and summer squash do best when watered to a depth of 45-60 cm (18-24 inches). Pumpkins, sweet potatoes and winter squash should be watered to a depth of at least 60 cm (24 inches).

To meet the watering needs of all the plants in your garden without wasting water, you may want to use a combination of watering devices.

Time of Day to Water

The best time to water is early morning. This is especially good in warm weather as it protects the plants from drying mid-day sun and keeps them from wilting. If you can’t water in the morning, the next-best choice is late afternoon, so that plant foliage can dry out before sunset. Wet foliage overnight encourages fungal disease, a risk especially in damp climates. Don’t water in the middle of the day when the sun is the hottest. This not only wastes water due to rapid evaporation, but hot sun on wet plants can damage leaves and fruit.