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.
As the weather heats up and plants reach full size, you may need to water containers (and especially hanging baskets) twice a day.
Both annual and perennial plants in the ground benefit from a good deep soaking up to three times a week.
Be Consistent
You should check the moisture level around the base of your plants. Determine the watering schedule you need to keep in order to maintain the right level of moisture. Watering every day or every two days doesn't matter nearly as much as consistent watering. Make a schedule and stick to it.
The roots will be damaged. Don't spray any plant during a heat wave. You will do the leaves more harm than good. Your goal is to minimize the stress they are under by protecting them from the sun if you can, and by watering deeply once a week to encourage deep root growth.
So, how hot IS too hot for plants? The general answer is around 90 degrees F, with some exceptions to the rule.
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.
Avoid full sun
In the current hot breezy weather it is probably best to water in the early evening. This gives the plants enough time to dry out, but there is still the chance for overnight water uptake by the roots. And if you want to water in the morning then start very early – before the sun is shining.
If you forget or are too busy to water your plants on some summer mornings, you can water them at night. However, this should not be your ordinary watering time. Morning is the proper time for watering plants, though you should keep in mind that not all plants need daily watering.
If the soil feels dry, it's time to water. In the spring and fall and in cooler climates, it might be sufficient to water container plants every two to three days. In the summer and in warm climates, container plants usually require daily watering, unless they are succulents or other drought-tolerant xeriscape plants.
Higher temperatures cause the plant cells which control the openings (stoma) where water is released to the atmosphere to open, whereas colder temperatures cause the openings to close. Wind & air movement: Increased movement of the air around a plant will result in a higher transpiration rate.
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.
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.
Watering container plants.
Pots absorb heat, which can stress plant roots, and the soil in them dries out much faster than soil in the ground. Container plants generally need to be watered daily. During really hot weather, you may need to even water twice a day, especially smaller containers.
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.
Watering Plants At Night Isn't Needed: Although the idea has been around for years, most plants don't need extra care by watering them at night. There are a few exceptions, but 99% of your plants, indoors and out should only be watered during the day.
Answer: Early morning (5:00 to 9:00 am) is the best time to water the garden when using a sprinkler, garden hose, or any other device that wets the plant foliage. When watering is completed, the plant foliage dries quickly. The rapid drying of plant foliage helps guard against the development of fungal diseases.
There's no cut-and-dry definition of a deep watering. Most gardeners generally refer to it as when water has soaked at least eight inches into the soil. This gives plants the structure required to survive lack of water, whether from a drought, a busy gardener, or other environmental stresses.
We should water the roots so that the plant grows healthy.
If you are unsure how long to water new plants, aim for 30-60 seconds for small plants – longer for larger plants while moving the hose to a few locations around the plant. Avoid watering when the soil feels moist. The earth must be allowed to dry out between watering.
For almost all plants, you should water them only when the top inch or so of soil feels dry. An easy way to check if your plant needs watering is to follow the finger dip test. Never be tempted to over-water. Over-watering is equally as harmful as under-watering.
Use shade cloth or protective row covers.
Sensitive plants like salad greens may require a 50 – 60% shade factor, while more heat tolerant plants like squash and beans may benefit from a 30% shade cloth. A shade cloth is temporary but care should be taken to position it to block sunlight while not reducing aeration.