Correct watering can make the difference between a bumper crop and complete failure. As we experienced earlier this summer, too much water can result in fruits and herbs having less flavor, increased disease problems, and plants drowning. On the other hand, if there is too little water, seedlings fail to come up, yields are reduced, and plants can die. Because correct watering relies on many factors, including weather conditions, soil type, and what you are growing, how much and when to water is not a simple formula. This article completes a three part series on water wise practices for lawns and gardens, discussing how and when to water vegetables, fruits, and herbs.
Understanding water needs
Fruits and vegetables are composed of up to ninety percent water that is absorbed from the soil by plant roots. If enough water is not available in the soil while fruits and vegetables are growing, plants will be stunted and may drop flowers or fruits, reducing yields. When rainfall does not provide adequate water for developing crops, gardeners have to supplement with irrigation to protect yields and quality.
The most critical time to water vegetables, herbs, and fruits is the first few weeks after planting or seeding. August is the time to sow seeds of many fall vegetables in the garden, including carrots, turnips, beets, spinach, lettuce, cabbage, collards, broccoli, and kale, as well as cool season herbs such as parsley, cilantro, and dill. Once seeds are sown, it is critical to keep the top three to four inches of soil moist until seedlings reach four to five inches in height.
For fruits and summer vegetables, it is also critical to water from the time plants bloom until harvest is complete. Water shortages during this time will reduce yields and cause fruits to be smaller than normal. Because they grow in the cooler times of the year, cool season crops usually do not require additional water unless we have unusually dry weather. This is most likely to happen in fall.
Perennial herbs such as oregano, thyme, and rosemary need less water than vegetables and fruits. Once established, these plants often thrive with no additional watering, even in sandy soils. Overwatering these herbs reduces their flavor intensity and can kill plants.
The best way to water vegetables, herbs, and fruits is by applying water to the soil using soaker hoses or a drip irrigation system. If you have a small garden or garden in containers, you can water plants with a watering can or watering wand attached to a hose. When watering by hand, avoid wetting plant leaves. Keeping leaves dry helps reduce foliage disease problems such as leaf spot and downy mildew.
Soaker hoses provide an inexpensive way to water your garden, but clog easily and usually last only a few seasons. Kits to install more durable drip irrigation systems are available from many garden centers and hardware stores. While more expensive initially, these systems are more reliable and cost effective in the long run.
When and how much to water
When watering edible crops, your goal is to avoid water stress by keeping the top six inches of the soil consistently moist. For most vegetable and fruit crops, this requires at least one inch of water per week from rainfall or irrigation during the growing season (April through October). When gardening in deep, sandy soils or during a heat wave, up to two inches of water per week may be needed.
Water applications should be split, to apply one half inch of water, twice a week. In very sandy soils where water drains quickly, three applications per week are often needed.
Plants grown in containers will likely need to be watered every day during summer, but only once or twice a week during winter and spring.
Reduce your garden’s water needs and improve plant growth by adding compost to the soil each year. Mixing compost into the soil helps soil hold water and nutrients. This is particularly important in sandy soils. In addition, mulching with leaves, straw, or bark mulch also reduces water needs and helps control weeds.
For gardening advice, visit ces.ncsu.edu, where you can post your questions via the ‘Ask an Expert’ link, or contact your local Extension office. If you live in PenderCounty, call 910-259-1235. In NewHanoverCounty, call 910-798-7660. In BrunswickCountycall 910-253-2610. Make a pledge to save water by taking the 40 gallon challenge at 40gallonchallenge.org/.
Charlotte D. Glen is the horticulture agent with the Pender County Cooperative Extension of NC State University, College of Agriculture & Life Sciences. She can be reached via e-mail at Charlotte_Glen@ncsu.edu.