Misting can be especially helpful on warm days when temperatures may get too high for plants and they may lose a lot of water. If you mist your plants in the morning, the water will evaporate off the surface of the leaf during the day.
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.
Misting creates humidity, and some tropical plants appreciate it (though there are more effective methods for increasing humidity around your plants), but it should supplement watering. To water properly, pour water directly on the soil until it runs out the drainage holes at the bottom of the pot.
To keep them cool, use old screens, lattice and sheets to shade vulnerable mature plants from the effects of mid-summer sun. Cover new seedlings with opaque covers to protect them from the sun until their roots are established. Commercial growers often use sprinkling to cool plants down.
As for misting — for the plants that need to be misted to thrive like air plants and ferns — it's best to mist them in the morning *and* the evening whenever possible. The morning mist helps to prepare them for the day ahead, while the evening misting helps create a little extra humidity.
Types of Plants That Like Mist
Tropical houseplants and plants that love high-humidity—such as the Chinese Evergreen, Boston Fern, and Majesty Palm—will benefit most from misting, says Plunkett. (Zebra plants, orchids, arrowhead plants, and begonias are just a few others that love mist.)
Letting the leaves get too wet and / or allowing them to stay excessively wet for a prolonged period of time can encourage mold growth on the leaf surface, so it's always important to ensure you don't ever allow puddles of water to form on your plants' leaves - this applies when watering as well as when misting.
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.
Signs Your Plants Are Too Hot
The leaves dry out. Excessively hot plants will dry out faster. The leaves turn yellow. One of the causes of yellow leaves is excessive heat, so this is one thing to consider!
Some plants want daily misting; others are OK with two to three times a week.
Misting is highly recommended at least once a month, and more often with species that enjoy it (see full list below). Be sure to spray the top and underside of your leaves, and if using for cleaning your leaves, wipe the leaves down with a cloth after misting to remove dust.
Some plant owners mist the base of the plant and the surface of the soil, but this has little benefit. Don't worry about misting the soil because the water won't make it to the roots to be absorbed. Just keep watering your plant as usual and be sure to focus your misting efforts on the leaves.
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 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.
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.
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.
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.
By regularly spraying your houseplants with water, you raise the humidity around their leaves, keeping delicate species from the tropical regions of the world happy in distinctly untropical homes.
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.
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.
“It does not raise the humidity, but it can be a part of your plant care in that it can be peaceful and soothing for you. But it does nothing for the plant.” Even plants that tend to like humidity naturally won't necessarily respond well to misting.
Ice-Cube Method. Just put two ice cubes on the soil in the plant, as they melt, your plant will get water without any mess.
Your Spider Plant will do well in normal household humidity but will thrive with a bit more humidity. Brown leaf tips may indicate the air is too dry, so mist your Spider Plant regularly using a Mister.