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.
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.
Cold weather prep for plants in winter
Drought-stressed plants are more susceptible to cold damage, so watering plants a few days in advance of a cold snap is beneficial. Watering just before the freeze can help too by creating warmth, and the water loses its heat slowly over the hours into the colder temperatures.
If you find tender plants covered in frost, try spraying them with water to wash the ice crystals away. Letting ice melt in the sun will cause irreversible tissue damage to the plant. Although it may survive, it will likely have deformed leaves, leaf spots, and uneven growth.
Throughout the winter your plant is still going to need some water. If the soil gets completely dry, the plant can die of desiccation. While regular watering isn't necessary, monitor the moisture level and water if the soil is dry.
Clip back to just above the living parts and get rid of the worst of the frost damage. Now you should leave the plant on its own to recover. Continue to water and care for it but remember to avoid too much pruning and fertilizing. Some people will actually wait until the following fall to fertilize again.
How long should I leave my plants covered during cold temperatures? You should cover plants until temperatures are back into the upper 40's to 50's. If it looks like a couple of days of cold temps, leave the coverings on for a couple of days.
Second, know that a light frost—32°F and colder—kills all tender plants such as tomatoes. Hardier plants such as spinach and kale will survive until there's a hard freeze—28°F and colder.
In cold weather, water should be trickled slowly into the soil. Water only when air temperatures are above 40 degrees F. Apply water at mid-day so there is time to soak in before possible freezing at night.
Farmers spray water before an overnight freeze because water produces latent heat when it freezes. The sprayed water on the surface of the plant will be converted to ice, and the heat trapped in it will insulate the plant from the cold environment.
The cold can mix badly with water, so just make sure the night time watering happens when temperatures are warmer. Late Spring, Summer and early Fall / Autumn generally have warmer months and this tends to mean overnight temperatures are warmer too.
When Should You Cover Plants? Cover your plants at night and remove them during the day when the temperatures rise above 32 degrees F, so that the soil can warm up again. Some outdoor plants won't survive the harsh conditions of winter, bring them inside and use these tips for caring for them through winter.
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.
Watering is the only thing that can help your plants recover but make sure not to overwater. If the frost damage is on plants that you should have brought indoors for protection, move them right away to their overwintering location. Give the plant a week or two to see if any plant parts have sustained permanent damage.
Freeze Warning - This is issued when there is at least an 80% chance that the temperature will hit 32 degrees Fahrenheit or lower. Light freeze - 29° to 32° Fahrenheit will kill tender plants.
A covered porch usually provides protection from light frost, but the garage or sun room is better for freezing temperatures. A couple days in darkness won't hurt the plant. Or move them out during the day and back in at night, if cold temperatures persist.
A freeze happens when air temperature dips below 32 degrees F. The colder it gets, the more damage you'll see to annual and perennial plants. A hard freeze is usually between 28-25 degrees F, and a killing freeze is 24 degrees F and below.
Cover Plants – Protect plants from all but the hardest freeze (28°F for five hours) by covering them with sheets, towels, blankets, cardboard or a tarp. You can also invert baskets, coolers or any container with a solid bottom over plants. Cover plants before dark to trap warmer air.
The easiest way to harden transplants is to place them outside in a shaded, protected spot on warm days, bringing them in at night. Each day, increase the amount of sunlight the transplants receive. Don't put tender seedlings outdoors on windy days or when temperatures are below 45° F.
To know when to cover your plants, you need to know when the plants you have are susceptible to frost damage. Some frost-tender plants need to be covered as soon as the temperature hits 32°F, while others can handle lower temperatures and/or longer freezing periods.
From that experience, I've found the best frost protection for your outdoor plants is either free or cheap. Cardboard boxes and brown grocery sacks make perfect frost cover and at the end of the season can be recycled. I keep various boxes on the patio and when frost is forecast simply put one over the plant.
Removing it will expose the still-living parts of the plant to future frost events. Additionally, removing dead foliage stimulates new growth. Future frost events will kill the tender new growth and possibly the entire plant. You may not want to, but you should leave those ugly dead leaves in place through the winter.
If you're worried about frost, move your potted plants under an overhang, a covered patio or into the garage, any place they have some cover, Hodel said. On still, cloudless nights, plants radiate heat into the clear sky and can become colder than the radiant air temperature.