How much water do you really need? When is the best time to water your vegetables? See the Almanac’s Guide to Watering Vegetables with a very helpful chart on how much water each vegetable needs and critical times to water.
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!
Before we talk about water, we must start with the soil which must retain that water. Healthy soil is the basis of healthy plants. If your soil is amended with organic matter (such as compost), you are well on your way to healthy 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
If your plants in the ground (versus a pot), the general rule is that plants need one inch of water per week. However, this does NOT mean watering one time per week. That doesn’t usually do the job. Plants do best when watered about three times a week, factoring in the rain. If the plants are seedlings, water twice a day until established.
But 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. See if the soil is dry an inch below the surface; that suggests it needs water.
It’s best to water early in the day while dew is still on the leaves so the foliage dries off by evening. However, if you can not water in the morning, watering in the evening is fine, too. Just avoid the middle of the day to avoid water loss to evaporation.
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. Light rain showers do not 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.
How to Measure One Inch of Water
So what is one inch of water per week? First, an inch of water is defined as a one-inch deep layer of water over the entire soil surfact that needs watering.
To measure one inch of water, you can either purchase an inexpensive rain gauge or try this DIY trick: Place 4 or 5 small containers (straight-sided) around the garden while the water during the rainfall. A tuna can is a good container to use. Mark 1 inch up from the bottom on the can. When 1 inch of water from rain or irrigation collects in the containers, that indicates that 1 inch of water was applied to the garden.
Again, don’t just rely on the “one inch” guideline. If the soil is dry an inch beneath the surface, your garden probably needs watering.
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 at least several inches down.
Water at the soil level if you can; watering from above causes leaf disease. 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.
- For a small garden, it’s fine to use a watering can, a watering wand, or a hose with a good nozzle that allows you to water right at the soil level near the plant.
- If you have more dense plantings or larger plants, lay your hose 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.
- If you have a larger garden with plants spaced one foot or more apart, consider investing in “drip irrigation.” This is 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.
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.
Watering Guide: Critical Times to Water and Gallons Needed
We recognize that folks with small mixed vegetable gardens aren’t going to water each vegetable differently. However, it’s very helpful to understand which vegetables are water lovers and the critical times when vegetables need water to thrive. If you plant vegetables in separate beds as we do (or in separate crop fields), it’s critical to give certain vegetables water at certain times.
|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 gallons per week depending on rainfall|
|Beets||Before soil gets bone-dry||1 at early stage; 2 gallons every 2 weeks|
|Broccoli||Don’t let dry 4 weeks after transplanting. Head development.||1 to 1 ½ gallons per week|
|Brussels sprouts||Don’t let soil dry out for 4 weeks after transplanting.||1 to 1 ½ gallons per week|
|Cabbage||Head development. Water frequently in dry weather.||2 gallons 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 (see left column)|
|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|
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.”
Free Online Gardening Guides
We’ve gathered all of our best beginner gardening guides into a step-by-step series designed to help you learn how to garden! Visit our complete Gardening for Everyone hub, where you’ll find a series of guides—all free! From selecting the right gardening spot to choosing the best vegetables to grow, our Almanac gardening experts are excited to teach gardening to everyone—whether it’s your 1st or 40th garden.