Talking About Preparing for Frost During 85-Degree Weather

Jugs on the transplants on the right offer insulation and protection from frost damage. Plants on left are waiting for their protection if frost threatens.

Repurposed deli tray tops provide frost and pest protection and accumulate daytime warmth to aid seed germination and growth of seedlings until they're large enough to remove the cover.

Old windows offer frost protection and accumulated daytime warmth. (Photo from the internet.)

Protected plant has outgrown its frost protection but may still be useful as pest protection if allowed to continue growing out of the jug.

     Yes, it’s definitely strange, talking about preparing for frost during 85-degree weather.  But that’s just another peculiarity in the world of gardening and especially during winter in Southern California.
     My Pasadena garden hasn’t had even “soft” frost – that briefly white light covering that appears early in the morning but disappears before the sunlight reaches it – for several years.
       But, with our evening temperatures continuing to edge down into the 40s, the prospect for frost resulting sometime in the next 2 months increases.    
     Frost may or may not happen this time around, but you’ll be really upset with yourself if your garden is damaged by a sudden bout of frost that you assumed wouldn’t happen.  And, you’ll be really pleased with yourself when you’re so relieved when the frost for which you prepared doesn’t materialize.
     So, on to some simple preparations that you can initiate if and when weather reports merit:
 
Water plants well, especially with our hot daytime temperatures and winds.
     The best frost protection for plants is to have sufficient water in the soil.  Plants that are fully hydrated resist frost damage better.
     But don’t fertilize plants until late January, since you don’t want to encourage new growth that might be damaged by frost.
 
Cover seedlings with repurposed plastic milk or water or soda jugs. 
     Cut off the bottom of the container, but save the top.  Snuggle the jug to left and right as you press it down into the soil around the small transplant.  This will create a mini-greenhouse environment to help the plant settle in, warming it during the day, holding some of that warmth into the early evening, and keeping out a couple degrees of cold through the night. 
     Using the top can be a bit tricky, however. Setting it loosely on top of the container through the chilly evening is fine, to enclose that extra bit of heat in the container for a couple of hours.  But, you must remove it early in the morning or you’ll have steamed plant shortly after the sun heats up the container. 
 
Cover growing beds with clear plastic sheeting.
     This will help concentrate daytime warmth and increase germination. 
     Be sure to anchor down the edges with soil or rocks to keep out slugs and others who love the succulent sprouts, and to keep the sheeting from blowing away. 
 
Cover tender plant foliage with large cardboard boxes, or drape old sheets or tarps on stakes over them.       
     Remove during the daytime so the plants can continue their photosynthesis.
 
Wrap citrus and other semi-tropical tree trunks with newspaper. 
     This will insulate against cold damage.
 
Cover tender plant foliage like bougainvilleas, fuchsias with plastic sheeting on stakes.
     Prop up the sheeting so it doesn’t touch the plant foliage, or it will conduct the frost directly to the foliage and damage it.
     Allow the bottom half of the plant to be open to the air.  Closing the sheeting may result in steamed plant.
 
Move dish cacti and succulents and potted trees under cover.
     Cold air falls directly down, so it’s most important to protect that space directly above a plant. 
     Rain also falls down, so best to keep cacti and succulents out of the direct line of the rain. 
     Both cacti and succulents and container plants require less irrigation during cold weather, with normal humidity providing sufficient moisture for the winter, unless it’s accompanied by wind, which dries out the plants.