As mentioned earlier, watering plants several hours before a freeze is the first defense against damage. During a temporary cold snap, cover entire shrubs with burlap, sheets or blankets for insulation. For the best protection, use a frame to prevent the covering from touching the plants.
Know Your Plants' Cold Tolerance
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. You'll need to look up each of your plants to verify its cold tolerance.
It's best to have covers in place before it starts to cool off. This way you retain the heat around the plant. Drape covering loosely to allow for air circulation.
Plants to move inside: Tomatoes, peppers, eggplant and others that will not survive frost. Plants to cover: Potatoes, radishes, spinach, leaf lettuce, beets, mustard. Plants that do not need to be covered: Onions, cabbage, broccoli, cauliflower, carrots, turnips, kale.
When should I wrap my plants for winter? This Old House landscape contractor Roger Cook suggests to start wrapping your plants in November. If your plants are new, be sure to cover them for the first two years. The older your plants get, the sturdier they become in surviving winters.
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.
During a temporary cold snap, cover entire shrubs with burlap, sheets or blankets for insulation. For the best protection, use a frame to prevent the covering from touching the plants. Extend the cover all the way to the ground to retain heat radiating from the soil.
So even though the weather forecaster isn't predicting a freeze, once temperatures start to drop below 40°F you need to be aware. Once temperatures drop below 40°F, you may want to start covering your plants with a frost blanket depending on what you're growing, which we'll get into in just a bit.
Early spring blooming flowers like crocus, snowdrop, and primrose can all survive the winter, and pansies are especially resilient. Violas, hostas, heuchera, irises, lily of the valley, cyclamen, and phlox also tolerate frost and provide some visual interest, as do catmint, baptista, sedum, and peonies.
If the soil is dry and the cold front is not preceded by rainfall, water the landscape before the freeze. Watering 24 to 48 hours before the freeze will elevate the night temperatures by 2 degrees. Don't overdo it. A soggy soil is not healthy for plant roots and will create root disease problems down the line.
If it stays cold for more than one night, can I keep my plants covered, or should I remove the coverings at some point? A. Our recommendation would be to remove the cold protection covering once temperatures are above 32 degrees.
Moist soil may absorb more heat and radiate it throughout the night. Cover plants before sundown to trap the stored heat from during the day. If you wait to cover it until after nightfall, the heat may have dissipated. Use frost cloth, burlap, drop cloths, sheets, blankets, or even newspapers to cover plants.
Four to six inches of bark mulch, straw, or shredded leaves - especially when placed around newly planted trees or shrubs - keeps soil temperatures constant and prevents plants from heaving out of the ground due to cycles of freezing and thawing.
Winter is usually the best time.
If you live in an area with distinct winters, the time when shrubs have lost their leaves and become dormant is an excellent time to prune them. Without the leaves, you can easily see the branching structure of the shrub and decide what to cut.
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.
After the freeze, you should be patient. Do not go straight for the pruners and cut everything back. It takes several days for plants to show us just how damaged they are. If plants are mushy and slimy, remove this material to prevent fungal infection or disease in the days to come.
Once the temperatures are consistently above freezing, it's time to remove the protective burlap coverings.
Despite the fact your plants are dormant and brown, they should still be watered periodically. Plants that remain dehydrated in winter months often don't survive until spring. Not only does this create extra landscaping costs in warmer months, it can actually damage your plumbing.
Hardy plants can be hardened off when the outside temperature is consistently above 40° F. Half-Hardy plants may be hardened off at 45° F.
I did some research and found out that houseplants need to be taken indoors before overnight temperatures dip below 45 degrees. Most tropical plants suffer harm from temperatures below 40 degrees. Well, we have temperatures forecast to dip into the 40s again on Thursday and lower 40s on Friday.
So, yes, it's been cold at night around Southern California, but folks, 45 degrees is a still a long way from the freezing temps that can burn our tender tropicals and other plants, like a multiday cold snap in 2007 that severely damaged crops in Central and Southern California.