Our coldest temperatures usually arrive just in time for Christmas. This year, the hard freezes that cause the most damage came early and suddenly, catching many gardeners by surprise.
Some garden centers and nurseries just received their stocks of frost-protection supplies last week. Keep your frost protection easily available — we're likely to have more freezing nights in the next few weeks.
Check the sky every winter evening; if the sky is clear, if you can see the stars and if the wind is calm, a frost is likely. Weather reports will tell us how low the temperatures will fall.
Our frost protection methods will change according to the lowest predicted temperature.
Wet soil stays warmer than the surrounding air. Keep frost-tender plants, especially citrus, well watered during the winter months. Deep irrigate by using a bubbler attachment on a hose for several hours during the day before a freeze is forecast.
Most unprotected frost-tender plants, even sub-tropicals like bananas, cannas and bougainvillea, can withstand a few hours of 30-degree temperatures, just below freezing without sustaining much damage.
A hard freeze with temperatures below 28 degrees will cause significant damage to unprotected citrus, sub-tropicals and winter-flowering annuals like begonias, pansies and snapdragons.
When temperatures are predicted to fall to 28 degrees, cover vulnerable plants at dusk with frost cloth (available at most garden centers) or old, washable blankets or towels, burlap, cloth tarps or cardboard. Use burlap or cardboard to wrap exposed trunks on citrus. Plastic transmits the cold; if you have to use plastic, make sure that the material doesn't touch the leaves.
Burlap, cloth materials and cardboard coverings should be removed during the day to allow warmer daytime air and sunlight to reheat the plants. Most frost cloth can be left over the plants for several days.
Banana and canna leaves turn brown almost immediately after freeze damage. Cut the brown leaves back to two or three inches high and use them, and tarps or frost cloth, to cover the tender stubs.
Leave the brown leaves on damaged plants like bougainvillea and begonias until all danger of frost has passed (in early March); the dead leaves will actually provide a small degree of freeze protection.
The extent of damage to citrus won't become apparent until new growth begins to appear in February. Wait to prune until then.
The same guideline also applies to most freeze-damaged plants-wait to prune out dead wood until new growth appears in spring.