It is best to water in the afternoon or evening the day after a freeze so plants have had a chance to slowly raise their temperature.
Water your plants
Watering your plants after a frost seems counterintuitive, but plant roots can't absorb any moisture from frozen soil. To avoid root damage, wilted leaves, and poor growth, just be careful not to overwater.
The evening
Don't do that. Evenings are best avoided because of evaporation and transpiration (I think of transpiration like a plant breathing). Around 99% of water a plant takes up does NOT stay in the plant. Tiny pore-like holes on leaves, called stomata, take in carbon dioxide and 'breathe out' oxygen and water.
If you have potted plants affected by a freeze, bring them indoors to recover. Do not put them in full sunlight but rather keep them in a cool room or even the garage. Moving a plant from 40-degree temperatures to the indoors with a 30-degree increase in temperature can also shock your plants.
On a cellular level, this means that as the water turns to ice, it expands, rupturing the cell wall. This is permanent damage, but it doesn't mean the plant will die. If the damage is isolated to a portion of the plant, it can be revived and recover.
Unfortunately, if you don't see any new growth, the plant most likely won't recover from freezing. “It most likely will be fine with some proper rejuvenation if not left out for the whole winter,” says Angelov. One final word of advice: Don't overwater a heavily pruned plant.
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.
This depends on the plant types, garden light conditions, and weather. Plants in shaded areas may last longer without water compared to those in full sun. Container and window box plants can dry out in a day, whereas many houseplants can manage with one watering per week or less.
The best way to tell if your plants need water is to stick your finger about an inch into the potting mix—if it feels dry, break out the watering can. If you detect dampness, check back again in a day or two. For smaller houseplants, you can also pick up the whole container. If it feels light for its size, add water.
It is best to water in the afternoon or evening the day after a freeze so plants have had a chance to slowly raise their temperature. After a freeze, soft-stemmed, non-woody plants such as impatiens, cannas, elephant ears, agapanthus, amaryllis, begonias, philodendron and gingers may be pruned back to living tissue.
You can check for life in woody plants by scratching the bark on the stems to see if it is green underneath, if you find green that branch is still viable and your plant is still alive.
The root of the trick's protection is a concept called "latent heat of fusion." When the water on the plant starts to freeze, it releases heat (a necessary process to turn water into ice), and that heat helps protect the plant.
There are, of course, many variables that can affect winter hardiness in a plant, but in general, my rule of thumb is as long as the mercury stays in the 20's at night and rises above freezing during the day, our plants should be just fine.
Thoroughly Water plants if it won't rain before the freezing temperatures arrive. It may sound illogical. However, the moist ground stays warmer than dry soil. Watering the night before the freeze will insulate the grass and plants' root structure and decrease the potential for cold injury.
Morning watering is actually preferable to evening watering as the plant has time to dry before the sun goes down. At night, water tends to rest in the soil, around the roots, and on the foliage, which encourages rot, fungal growth, and insects.
“Most plants will typically be fine if you're gone a week, but some may start to suffer if they go without water for two weeks,” says Justin Hancock, Costa Farms horticulturist.
If you have left your plant without water for a week, then bottom watering is the best way to revive it.
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.
Covering plant material at temperatures between 39-30 with freeze cloth or covering can be effective. Prolonged exposure at temperatures of 28 degrees and below will notice protection results diminish with each degree dropped.
With each year's winter setting new records for extreme temperatures and unusually late cold snaps, many farmers who have never previously considered frost protection are exploring their options. Spraying your plants with a steady stream of overhead water is a well-tested and proven way to prevent frost damage.
Light freeze - 29° to 32° Fahrenheit will kill tender plants. Moderate freeze - 25° to 28° Fahrenheit is widely destructive to most vegetation. Severe or hard freeze - 25° Fahrenheit and colder causes heavy damage to most plants.
Use sanitized pruners, start at the top or tips and work your way down to live areas. Prune dead stems and canes all the way back to the base or trunk. Prune partially living branches to a juncture. Young trees or those with thin bark can also be affected by cold temperatures.
If you're looking for tips for protecting your plants from frost, avoid using garbage bags as plant covers. Trash bags are not the best protection against frost damage, primarily due to their material. Most garbage bags are made out of low-density polyethylene plastic.
You can provide cover to plants by placing potted plants in a garage or shed. Protect landscape plants by using mulch, burlap, sheets, blankets, or – even better – plant freeze protection tarps.