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. Mist leaves with a spray nozzle to cool down plant and reduce transpiration.
So, how hot IS too hot for plants? The general answer is around 90 degrees F, with some exceptions to the rule. This means that when temps rise above 90 and remain there for a lengthy spell: Leaves wilt.
Cold Temperature's Effects On Plants and Vegetation
MODERATE FREEZE: 25 degrees F to 28 degrees F / -4 degrees C to -2 degrees C. Wide destruction on most vegetation with heavy damage to fruit blossoms and tender semi-hardy plants. SEVERE FREEZE: 24 degrees F / -4 degrees C and colder. Heavy damage to most plants.
Focus on plants that love the heat.
These include: tomatoes, eggplant, melons, peppers, malabar spinach, cowpeas, and lima beans. Sweet potatoes, okra, and southern peas can handle the most heat.
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.
Plants can cool themselves by pumping water out through the leaves for a kind of swamp cooler effect. They can also make “heat-shock” proteins which reduce problems from overheating. All these strategies do take resources away from a plant's other needs like growth, flowering and fruiting.
Most houseplants are tropicals and prefer temperatures between 65-75°F during the day and about 10 degrees cooler at night. For many plants, temperatures below 50°F can cause problems.
Plants can be damaged by either high day or high night temperatures and by either high air or soil temperatures. A plant's temperature usually runs just above the air temperature. Trees and shrubs enjoy optimum growing conditions when the temperature ranges between 60 - 85°F.
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.
The short of it is that your plants need more water in extreme heat, but it's not just the amount of water that matters. Plants also need water to be applied in the most beneficial way. Plants are amazing organisms. They will do most of the heavy lifting.
There is a high likelihood that plants are experiencing heat stress if they wilt during the day's hottest period and then revive in the evening or morning. Dried Leaf Margins. Some types of crops dry off the leaf's outer edges to ensure survival.
If extreme heat continues for weeks at a time, plants can actually die from a depletion of their food reserves. Finally, high temperatures may simply cause severe water loss (desiccation) when transpiration (the process by which leaves release water vapor to the atmosphere) exceeds moisture absorption by the roots.
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. Mist leaves with a spray nozzle to cool down plant and reduce transpiration.
These studies show that root growth slows down or stops when soil temperatures get above 86 degrees Fahrenheit and roots will die when soil temperatures get above 96 degrees Fahrenheit. When temperatures outside are well over a hundred degrees, it's easy for the soil in pots to exceed these temperatures.
"Because most houseplants come from tropical or subtropical areas, it's best to wait to take them out until night temperatures don't drop below 50°F or so," says Hancock. Once you move them outside, it's generally safe to keep them there until the nighttime temperatures fall below 50°F again.
However, when there is a heat wave and soil temperatures increase, plant roots are less able to compensate for varying levels of soil moisture within the soil profile. When soil temperature rises above an optimum threshold, plant water and nutrient uptake can be impeded, causing damage to plant components.
When. Hands down, the best time of day to water is early in the morning. Watering during the day can increase risk of disease. If you can't water early in the morning, water late in the evening, especially before days forecasted to have dangerously high temps.
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.
In extreme heat, be sure to water the plants deep enough to keep the plants moist for as long as possible. A quick spray of your plants is not enough in extreme heat. Make sure to water deeply. Watering less often, but deeper, is far more effective than spraying the surface more often.
If you're outside, find shade. Wear a hat wide enough to protect your face. Drink plenty of fluids to stay hydrated. Avoid high-energy activities or work outdoors, during midday heat, if possible.
Keep cool. Seek out air-conditioned buildings, draw your curtains, use a fan, take cool showers and dress in light and loose clothing made from natural fabrics. Plan ahead. Schedule activities in the coolest part of the day and avoid exercising and being outdoors in the heat.