Vegetables and fruits that are developing fruit during a heat spell need regular watering to ensure good production. Vegetables typically require daily watering during summer weather, but may need a second watering when temperatures are extremely high.
During extremely hot weather (daytime temperatures above 90F and nighttime temperatures above 70F), try to water daily or every other day. In a 10x10-foot garden, this would mean giving your plants 8 to 9 gallons of water each day.
Water plants deeply, ideally first thing in the morning while temperatures are still low and transpiration rates are low. Potted plants will probably want to be watered more than once a day during a heat wave. The next best time to water during hot weather is in the early evening.
In hot weather you need to water in the mornings when it is cooler. This will allow more water to reach the root system before it evaporates in the heat.
During spring and summer in Southern California, she suggests drip watering three times a week for 18 minutes, then adjusting from there if the soil is too wet or dry. Don't know how to tell? Stick your finger in the soil. If it's consistently moist 2 inches down, your plants are fine.
Containers dry out more quickly than garden beds, so it's best to increase watering in the summer. During heatwaves, water container plants twice a day, once in the morning to give plants a boost before the sun begins to bake down, and once in the evening to replenish what the day took away.
While deep watering a couple of times a week is typically best for tomato plants, a heat wave is not a typical situation. During hot weather, water your tomato plants daily, but give them less volume. You can return to twice-weekly deep soakings when the temperature breaks.
During really hot weather, water your vegetables at least two to three times a week. Watering the garden deeply is critical. The water must go down, down, down to encourage deep roots and get away from the hot soil surface.
Established Plantings
Use a soaker hose or sprinkler for 30-60 minutes at a time. During normal summer temperatures, this type of watering can happen every 2-3 weeks. In times of extreme heat, 1-2 times each week may be necessary. Know your plants though!
And most importantly, plants absorb water more readily when they're not under heat stress—a condition that's more likely to occur when the sun is at its peak. So while it's perfectly okay to water plants while they're in full mid-day sun, it's not the most efficient way to go about it.
The best time to water plants is in the morning or evening.
More importantly, watering at these times actually helps the plant retain water. If you water in the afternoon, especially during summer, the heat and sun are at their peak and the plant's water will evaporate instead of absorbing into the soil and roots.
Watering in the heat of the day is not a good idea as much water is lost through evaporation from the surface of the soil and the plants will use water more efficiently if watered in the cooler parts of the day.
The best time to water outdoor plants is in the morning when temperatures are usually cooler. This gives the plants time to absorb the water so they can get through a long, hot day. The second-best time is late in the afternoon or early in the evening. Try not to water at night.
Mulch, mulch, and mulch some more!
Cover your soil with a blanket of organic material such as straw, leaves, shredded paper or cardboard, or bark. This will moderate soil temperature, prevent runoff and evaporation, and hold moisture in the for longer periods between waterings.
So, how hot IS too hot for plants? The general answer is around 90 degrees F, with some exceptions to the rule.
Quick facts. Water your garden so that your plants always have enough moisture. On sandy, well-drained soil, you may need to water twice a week. For soils that hold moisture, such as heavier clay soils, or loamy soils rich in organic matter, watering once a week is fine.
Avoid watering when temperatures are below 40°F or when sustained freezing temperatures are expected within 24 hours as this water will freeze and not be available to the plants.
Deep soaking two to three times a week—considering rainfall—will promote healthier, more productive growth than frequent shallow watering. The best way to know if your vegetable garden needs water is to stick your finger down into the soil a couple of inches. If it feels dry, water.
In the blazing summer, when temperatures are between 90-100+, try watering 3-4 times a week.
So, it's best to water them in the morning before the sun hits them. In high heat and drought, I water them again in the evening. If your tomatoes wilt in the heat of the day even though you have watered them well in the morning, the cause is not lack of water.
Too much standing water and moisture on the plants themselves is going to create a host of problems. By watering early in the morning, you will create an efficient routine that works in tandem with the plant's natural biological functions. Avoid watering in the evening at all costs.
One of the most frequently asked questions we get is how much water to use and how frequently do you water the plants. We recommend watering your plants twice daily -- early morning and late afternoon. To be more specific, early morning means 7-10am; and late afternoon means 3-5pm.
How Long To Water Your Garden. Adjust your watering schedule based on specific plant needs and the seasons. In the summer, I either water with a slow drip for 1 hour every three days or 30 minutes every day. In winter, I might go a month or more without watering.