Most plants grow best in temperatures ranging from 59°–86°F. When temperatures above 90°F are sustained for long periods, plant growth is slowed, and some plants begin to show signs of stress.
What Temperature Do Plants Require? Most prefer a temperature range of 60-70° F at night and 75-80° F during the day, though many can handle as low as 40° F.
So, how hot IS too hot for plants? The general answer is around 90 degrees F, with some exceptions to the rule.
Tomatoes, peppers, eggplant, corn, melons and squash actually need at least a month of 80 to 90 degree weather to develop a flavorful and abundant crop. As long as they don't run out of water, these sun worshippers are well equipped to survive the heat.
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 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.
When To Stop Watering Plants in Fall. When the air and soil temperatures consistently fall below 40 F, it's time to stop watering. The ground can't absorb water once the top few inches freeze. Continue to water your plants up until this point so they're as well-hydrated as possible going into winter.
The books are right – planting in the summer when it is hot and dry is not the best time to move new plants into or around the garden. During a particularly bad heat wave it can be hard enough to keep the soil hydrated, let alone provide ample moisture for plants that are establishing new roots.
Most plants tolerate normal temperature fluctuations. In general, foliage plants grow best between 70 degrees and 80 degrees F. during the day and between 60 degrees to 68 degrees F.
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 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 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.
Flowering temperature is ideally at 84 - 85 °F. This will help keep leaf temps at the Cannabis-ideal 88 degrees when using our LED grow lights. Vegetative temperatures can range from 75°-90°. However, ideal vegetative growth will occur at 85 °F and 60-70% humidity.
Mid to late flowering stage
It's also important not to exceed around 82ºF(28ºC) unless you're supplementing with CO2. Once you know how to detect grow room temperatures that are too high and the temperatures you should aim for, it's time to cool things down.
It's safe to move your plants outside when the outdoor temperatures stay consistently above 50°F. Pay attention to the weather report. If nighttime temperatures are set to fall below 50°F, bring your plants in for the night.
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.
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.
The general rule of thumb is that most plants freeze when temperatures remain at 28°F for five hours. Of course, there are exceptions to this rule. Seedlings, with their tender new leaves, often give up the ghost when temperatures dip to 32-33°F. Tropical plants have differing low-temperature thresholds.
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.
Plants do best when watered deeply about three times a week, factoring in the rain. If the plants are seedlings, water them twice a day until established.
Most of the houseplants we grow originated in the tropics or sub-tropics where rainfall is relatively warm. Ice cold water will cause root shock, which may lead to permanent root damage, leaf drop and other problems. Allow the water to warm to room temperature before watering the plants.