How much water do you really need? When is the best time to water your vegetables? See our tips on watering your garden—plus, a chart of when and how much to water specific crops.
According to some experts, less is often more when it comes to watering your vegetable crops. In areas without drought, a common mistake new gardeners make is watering too much!
Start With Good Soil
Healthy soil is the basis of healthy plants. You can’t just dig up dirt and put in plants. If you add a little mulch or compost, you are well on your way to making rich, well-balanced soil.
Regular applications of modest amounts of compost—one-quarter inch per season—will dramatically improve your soil’s water retention and help suppress disease. See our articles on soil types, soil testing, and the basics on amending your soil with NPK fertiliers and organic amendments,
When to Water
Don’t just water without thinking. Feel your soil! When the soil sticks in your hand and you can form it into a ball, it is moist enough. But, if it barely holds together in the palm of your hand, or if the surface looks hard, baked, or cracked, it is probably dry and it’s time to water.
It’s best to water early in the day so the foliage dries off by evening. When the plants are watered at night, the foliage stays wet for a long period of time and disease problems build up.
Believe it or not, sometimes the best time to water is during or immediately after a rainfall, especially if the rain shower amounts only to a half-inch or so of water. The reason for this is that you want to add sufficient water at the same time to ensure penetration down to 5 or 6 inches. If you wait another day or two to water, you will be adding only surface water, which evaporates rapidly. With only frequent, light watering (or rain showers), you never build up a reserve of water in the soil.
Lose Your Guilt About Wilt
Another sign is that the plants may wilt and look especially droopy. However, temporary wilting during the heat of midday does not mean that it’s time to water. Some plants go through an obvious midday slump, especially on very hot days, which is an indication of the plant’s natural adaptation to its environment. Visit your garden again in the early evening and see if the wilted plants have regained some turgidity. If they have come back—that is, if they look perkier—do not water.
Watering Guide: Critical Times to Water and Gallons Needed
To address the big watering question, below is a chart that tells you critical times to water each vegetable crop as well as the number of gallons of water needed.
This watering guide assumes summer vegetables and good, moderately-rich soil. Water less often in cool spring or fall months. Water more often in hotter, dryer periods.
|Needs a lot of water during dry spells.||Needs water at critical stages of development.||Does not need frequent watering.|
|Vegetable||Critical time(s) to water for a 5-foot row||Number of gallons of water needed|
|Beans||When flowers form and during pod development||2 per week depending on rainfall|
|Beets||Before soil gets bone-dry||1 at early stage; 2 every 2 weeks|
|Broccoli||Don’t let dry 4 weeks after transplanting. Head development.||1 to 1 ½ per week|
|Brussels sprouts||Don’t let soil dry out for 4 weeks after transplanting.||1 to 1 ½ per week|
|Cabbage||Head development. Water frequently in dry weather.||2 per week|
|Carrots||Early root enlargement. Before soil gets bone-dry||1 at early stage; 2 every 2 weeks as roots mature|
|Cauliflower||Head development. Water frequently for best crop.||2 per week|
|Celery||Water frequently for best crop.||2 per week|
|Corn||When tassels form and when cobs swell||2 at important stages (left)|
|Cucumbers||Flowering and fruit development. Water frequently.||1 per week|
|Lettuce/Spinach||Water frequently for best crop.||2 per week|
|Onions||In dry weather, water in early stage to get plants going.||½ to 1 per week if soil is very dry|
|Parsnips||Before soil gets bone-dry||1 per week in early stages|
|Peas||When flowers form and during pod-forming and picking||2 per week|
|Peppers||Steady supply from flowering through harvest||2 per week|
|Potatoes||Tuber set and enlargement when the size of marbles||2 per week|
|Radishes||Plentiful, consistent moisture for root enlargement||2 per week|
|Squash||Water frequently for best crop.||1 per week|
|Tomatoes||For 3 to 4 weeks after transplanting and when flowers and fruit form||1 gallon twice a week or more|
How to Measure Your Water
Another way to figure out how much water it follow a general rule of thumb of one inch of water per week.
To measure overhead sprinkling, place 4 or 5 small containers (straight-sided) around the garden while the water is being applied. When 1 inch collects in the containers, that indicates that 1 inch of water was applied to the garden. Gardeners can recording the time needed to fill the container for timing future waterings.
How to Water
What you want in a healthy plant is deep root penetration, and the only way that you’re going to get deep roots is if there is water down deep.
Start at the very beginning: Saturate each plant hole when you transplant seedlings. When you do water, make sure that you get the soil saturated enough that the moisture percolates several inches down.
The disadvantage of using a sprinkler is that foliage is wetted by water dispersed via overhead application. This could lead to foliar diseases since the foliage remains wet for extended periods of time. An alternative is to lay the hoses directly on the ground near the plant so the water goes where it is needed. A board or rock placed under the water flow will prevent the water from eroding the soil. A good way to direct the water to the plants is to dig a little trench around the plants and allow water to flow into it.
Drip or trickle irrigation is also successful in the home garden. This is done mainly with hoses or plastic tubes with small holes in them that deliver a relatively small amount of water directly to the root zone; by supplying optimum moisture, periods of water stress can be avoided. The hoses or tubes are placed down the rows and water slowly trickles out. Regardless of method chosen, be sure to apply sufficient moisture.
Don’t Forget to Mulch!
Mulching is perhaps the #1 water-conserving technique for areas that receive less than 40 inches of rainfall annually. Organic mulches reduce evaporative moisture losses from the soil surface, and because the soil stays cooler, they also reduce transpiration water losses. Lay a thick layer of mulch down on top of soil. (Do not mix with soil.) Renew mulches that are in place for the entire growing season.
Don’t baby your crops; plants are incredibly adaptable. They have the ability to draw water from deep in the soil. Periodically, take a trowel and dig down several inches into the zone where the roots are most active. If the soil there is still moist, there would be no benefit from watering.
For more on watering the garden, especially in drought, read our article on “The Water-Wise Garden.”