Reviving Plants After Frost Damage
Yes – severe frost bite could leave a portion of the plant dead, but the stem and roots might still be in good shape. Your first instinct is probably to prune the dead parts to allow for new growth, but we recommend waiting until you're sure you've seen the last of the spring frosts.
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.
The amount of damage depends on the severity and duration of the freezing temperatures. If you have light freezes for short periods of time, plants can usually recover. After hard, long freezes, there's no guarantee. After the freeze, you should be patient.
In order to preserve flowers so they'll last when you take them out of the freezer, you'll need to freeze-dry them.
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.
When it's freezing, water in plant cells freezes too. This can destroy them because they dehydrate. One would think that if the sun comes out, plants will find the strength to resuscitate again, but they are actually shocked. Since their cells are damaged, the quick defrost will only destroy their stems and leaves.
Once open, use cool water (or simply add some ice cubes to the vase) in order to keep the blooms lasting longer. Though water still absorbs into the stem, colder water slows any decay, bacteria, or mold from breaking down the organic matter.
Flowers can be particularly sensitive to their environment. Even if they are quite hardy, they can still wilt prematurely if they are exposed to extreme conditions. Some flowers do enjoy cooler temperatures than others but, for the most part, near freezing temperatures will do more harm than good.
The easiest way to protect from a freeze is simply by covering plants with a sheet or a blanket. This acts like insulation, keeping warm air from the ground around the plant.
"You should use hot water [defined as 100 degrees] as a last resort if flowers are severely dehydrated. Some stems respond better to being hydrated in hot water, like hydrangea, dahlias and viburnum, and you can also use hot water to make some blooms, like peonies, anemone and roses, open faster," Lachnit-Fields says.
Also, soil that is saturated with a sugar solution can attract harmful micro-organisms that can affect the plant's health. There is no scientific evidence that feeding plants sugar water is conducive to plant health, on the contrary, it can harm your plants and even kill them.
Cut your stem at a 45-degree angle and hold in boiling water. The hot water forces the oxygen out of the stem and you'll see the tiny bubbles popping up. Once the bubbles taper off you can plunge the flowers straight into fresh water to keep them healthy. They'll be able to drink up perfectly!
Generally, wait until spring when new growth appears, and do your pruning when you can clearly see what is alive and dead. If you're impatient, use your thumbnail to scratch the bark starting at the top of the plant and working down. If the tissue just under the bark is tan or brown, that branch is dead.
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.
Symptoms of freeze damage include shriveling and browning or blackening of damaged tissue. Damaged growth usually becomes limp. Eventually, damaged or destroyed leaves drop from the tree or shrub. Fortunately, trees and shrubs have the ability to leaf out again if the initial growth is damaged or destroyed.
Damage control
Once frost damage occurs, nothing can be done to reverse the damage. 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.
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.
While the damage to the leaves is permanent, plants are pretty resilient. If the leaves are severely damaged, they will die and fall off. New leaves should take their place. It may take several weeks or months to see full recovery, but given warmth, proper light and water, most plants bounce right back.
Soda. Pour about 1/4 cup of your leftover soda into the water in a vase full of cut flowers. The sugar in the soda will make the blossoms last longer. Use clear soda if you have clear vase, like Sprite or 7-Up.
Florists use warm water only for resuscitating wilted flowers, because warm water is absorbed quickly. For restoring wilted stems, hot water (110 degrees Fahrenheit) is recommended.
“Much like fruit and vegetables, cold temperatures extend their shelf life.” If you have fresh cut flowers in a bouquet that you're putting straight into a vase to use as a centerpiece in your home, go with cold water. This way the beautiful arrangement will last longer.