The best time to water your garden in summer is from 6 am to 10 am—before the heat of the day sets in, giving your plants plenty of time to drink up and any moisture on the leaves to dry off before nightfall. What is this? If watering in the morning isn't possible, the next best time is from 4 pm to 7 pm.
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.
Most plants shut down during extreme heat, so if it is over 100 degrees, it may be best to wait to water even if your plant is stressed. Throw a damp sheet over it, or mist it lightly to bring the temperature down.
The notion that wet leaves on sunny days cause scorch in plants was disproved nearly ten years ago. But there is no doubt that watering in full sun is not water efficient – as much of it will evaporate before entering the soil. In the current hot breezy weather it is probably best to water in the early evening.
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.
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.
Avoid Overwatering Tomatoes in Summer Weather
Tomato plants need an inch or two of water a week, and a deep soaking is better than a little water every day. Regular watering helps prevent tomatoes from developing cracks. Too much water will suffocate plants' roots.
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. And when weather is hot, consider providing relief for plants with shade cloth, particularly from 10 AM to 2 PM during the heat of the day.
Watering in the heat of the day shouldn't hurt the plants -- it actually cools them off -- but it's a far less efficient use of water as much of it will evaporate before reaching the roots.
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.
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. There may be times when you cannot schedule watering in the morning. In this case, water the plants in the late evening before bed.
So, how hot IS too hot for plants? The general answer is around 90 degrees F, with some exceptions to the rule.
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.
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.
As the weather heats up and plants reach full size, you may need to water containers (and especially hanging baskets) twice a day. When you water containers (or plants in the ground), check that the soil is actually dry before you water.
A good general guideline when it comes to watering your plants is an inch of H2O per week, either by rain or watering; in arid climates, it is double that. In hot weather, vegetables need even more water, up to about ½ inch per week extra for every 10 degrees that the average temperature is above 60 degrees.
In times of extreme heat, 1-2 times each week may be necessary. Know your plants though! Some plants prefer almost zero water during summer (manzanita, Ceanothus, madrone and cistus) and others wilt even when they have ample water (hydrangea, rhododendron). So adjust watering accordingly.
To the gardening world it may have always been considered a fact, but science has never proved the widely held belief that watering your garden in the midday sun can lead to burnt plants.
When temps consistently hit the 95-degree range, tomatoes tend to stop producing red pigments, which means typically red fruits may instead ripen to orange. When high heat lingers with days above 100°F and nights over 80°F, most tomato ripening stops altogether.
Watering in the morning is ideal from a water efficiency standpoint (less evaporation/water loss), and it also gives the foliage plenty of time to dry out (not a problem if you're using drip irrigation). Overhead irrigation of tomato plants late in the evening or at night is a no-no.
So, how often should you water tomato plants? Tomato plants need to be watered daily or every other day unless you have had recent rain. The plants need 1-1.5 inches of water per week, but container-grown tomato plants need to be watered twice per day.