Calvin Finch, Conservation Division, Manager, Water Resources &
Conservation Dept., SAWS, and Horticulturist
If you are like me you probably were spoiled by the series of mild winters we have had and neglected to properly protect your tender container plants from the freeze after New Years. The question becomes, Did my bougainvilleas, plumeria, tropical hibiscus, and blue daze survive, and what should I do now?The answer is, It depends on what condition they were in before the freeze and how sheltered the location was.
Plants that had lush, new growth when the freeze hit or were dried out are most likely to be severely damaged by the freeze. Plants protected by the house or in locations where heat is retained fared better than plants in the open and/or low spots.
The freezing temperatures were low enough (22 degrees F.) and lingered long enough (nearly 24 hours in some neighborhoods) that some of the plants were killed. Many more, however, have probably had their tops killed, but the roots may still be alive. The safest thing to do is to get the tender plants to shelter now.
It is best to wait until just before the plants are moved back to the patio to severely prune them, but some pruning now is okay. To make my bougainvilleas fit in the greenhouse I prune them severely. The pruning also reduces the number of wounds that the thorns inflict on unwary gardeners trying to move them into shelter.
If you do not have a storage space that is freeze proof, move all the container plants to the most sheltered location on the patio or near the house. I like locations surrounded on two sides by walls. Eastern exposures are best, southern exposures are second best. Cold north winds are obviously a threat to a plant, but the effect of a western sun after a cold night will also damage plants.
If all the containers are close together, it is easier to throw a drop cloth or agricultural fabric over the plants if freezing temperatures are forecast.
This is the first winter in a while where the root-hardy perennials were completely frozen back. In my yard plumbago, lavender lantana, Mexican heather, salvia, and Katy ruellia were frozen back. They can be cut back to the ground anytime now, but I like to leave them until the end of February in order to provide shelter for foraging birds.
In the flower garden the snapdragons, petunias, calendula, and stocks lost their blooms, but the foliage is fine. They will bloom again in February, March, and April. The pansies and cyclamen weathered the freeze and are blooming well.
When temperatures are cold, plants do not use much water, but it is important to keep winter hardy plants from drying out. Since the days are so short we go to work in the dark and return in the dark, and it is easy to forget plant care. Every Saturday make the rounds to feel the soil. Water those plants where the soil is dry to one inch.