cover plants for frost protection

Q: I transplanted three rubber plants that are all at least 10 years old into my yard. Then snow fell for almost 36 hours, and it seems to have taken a severe toll on each plant. In addition, the temperature drops down to between 24 and 32 degrees every night. Is there anything I can do to attempt to salvage them? Is there a way to try to keep them warm?
– Tina Barr
Apple Valley
A: This winter’s cold snap came a month earlier than usual and was nastier than anything we had experienced in several years. Ficus trees such as the rubber tree (Ficus elastica) were hit particularly hard, whether in Apple Valley or Woodland Hills. Depending on cold severity, damaged leaf stems, and even trunks may have a water-soaked or burned appearance. There is really nothing you can do to salvage cold-damaged plants other than prevent them from suffering further damage. You can either wrap your plants in old blankets or burlap, or build them simple protective mini-greenhouse frame structures covered in plastic. If you wish to keep your mini-greenhouses in place all the time, you should use clear plastic film, but if you just want to put them over your plants at night, then the plastic can be either clear or black.
During the day, the ground is warmed from the radiant heat of the sun. At night, this heat radiates back up from the ground into the sky. As long as you have plastic to block the escape of this warm air and keep it around the plant, you should be all right.
I know someone in Granada Hills who grows bananas and mangoes, and protects them from the cold under individual plastic “cages” during the winter. He protects other tropicals under booths covered with fine mesh shade cloth. Of course, day and night temperatures also need to be taken into account. In northern states, some plants are kept wrapped in blankets all winter long.
The fact that your plants are 10 years old gives them a better chance at surviving a freeze than if they were babies. Whatever you do, refrain from pruning off dead growth until spring weather returns. Pruning encourages new growth, which would be smitten in another freeze.
TIP OF THE WEEK: If freezing weather is forecast, check the evening sky. A clear sky is more of a threat than an overcast one. Clouds trap heat and prevent it from dissipating completely. One strategy for combating a freeze is to soak your garden well. On a night where the temperature hovers around 32 degrees, considerable heat is released as water turns to ice. In this regard, drip irrigation is especially effective in keeping plants warm on cold nights. Where citrus is concerned, spraying the fruit with water also offers a measure of frost protection.

Photo credit: inkandpen / Foter.com / CC BY-NC-SA