Saturday, December 7, 2013

What to Do After a Hard Freeze

Sometimes a gardener feels as if they're in a heavyweight boxing match: Your Tender Plants vs. Mr. Freeze. Your citrus, succulents and perennials that may thrive in milder climates might be able to take a frosty punch or two here in the Sacramento/San Joaquin Valleys, foothills, and inland portions of the Bay Area. But five or six chilling blows to the flowers, leaves, stems and roots? 

We aren't talking about light frosts, or temperatures that hover around 30 degrees (F) for a couple of hours; that would be normal for this time of year. What area gardeners are going through right now is a week of extended hours of below freezing overnight temperatures, with prolonged bouts of plant-killing cold in the mid-to-low 20's. 

So, what should a shivering gardener hard freeze? Should they:
a) remove all plants that look frost-bitten; 
b) prune away all freeze-damaged plant parts;

c) Purchase and plant again this month those same varieties of trees, shrubs, perennials and annuals;
d) Water the garden, even if the plants resemble toast;
e) Fight the urge to prune and plant by staying indoors, next to the wood stove.

The answers happen to be the easiest to accomplish on a cold weekend: d) and e).

If plants in your garden look blackened and wilted now, new growth may emanate from the base of the plant when the weather warms up in a couple of months.

New growth beneath the frosted branches of a geranium.

Pruning away the dead portions now exposes buds that may still be alive; another frosty morning could wipe out those survivors. 

The average frost season for Sacramento is about two months, primarily December and January. But temperatures below 32 have been recorded as early as the first week in November; as late as the third week in March.

So, keep the shears in the garage and let the dead portions of the plants protect the understory.  

It may take until mid-Spring before you see new growth. Patience is key before you pick up the pruners. In the meantime, tolerate the ugly.

Make sure your garden and potted plants remain moist, especially if it isn't raining. Water gives off heat, and this can protect plants from freezing, especially borderline citrus trees, such as lemons and limes. Damp soil retains heat better than dry soil, protecting roots and warming the air near the soil.

Succulents, such as cactus, are the exception, however. According to the Arizona-based Desert Botanical Garden, most succulents survive freezing temperatures best if the soil around them is dry. 

It's dead, Jim.
Some of those dead plants may be summer annuals, such as this impatiens, which took its sweet time to croak. Mornings hovering around 25 degrees can do that to a summer annual. Put them in the compost pile; plant more in the spring, after all danger of frost.

Frosty the Ficus

What about those plants that have frozen past the point of no return? Should you replace them with the same varieties? That frozen ficus (or avocado tree) may be Mother Nature's way of telling you: "Hey! This ain't San Diego! Pick outdoor plants that can take colder temperatures!"

Oh, and keep your frost protection gear handy...just in case.

Sunday, December 1, 2013

Hard Freeze Forecast for Dec. 4-7

The National Weather Service has issued a hard freeze watch for many areas of Northern California for Wednesday through Saturday, Dec. 4-7.
Freeze Protection for Lemon Tree
Here is that warning, in its original ALL CAPS glory:




Frozen Hosta



  Many of us learned to take this seriously in 1990, when consecutive low morning temperatures of 22, 18, 21 and 23 in Sacramento descended upon us during the period of December 21-24. Temperatures did not get above 25 degrees in parts of the San Joaquin Valley for three to five days and all time record low temperatures were set at Sacramento, Stockton, and Bakersfield. Many records were set for duration of freezing temperatures. The agricultural industry was devastated as acres of trees, not just fruit, were destroyed. Thirty-three counties were disaster-declared.

Homeowners back then learned which plants don't like it cold (hibiscus, geraniums and other plants popular in the Bay Area and Southern California); and, which plants were the hardy survivors (another reason the oleander was chosen for the Highway 99 median strip).
The National Weather Service has a nifty Tabular Forecast chart link within their "Additional Forecasts and Information" list at the bottom of their local forecast page. This tabular chart predicts the temperature, hour by hour, for the selected location, for the next six days. This is probably more useful for predicting the duration of freezing temperatures, rather than the actual temperatures themselves. When those durations exceed four hours at temperatures of 28 degrees or less, that's when plant damage can become fatal to sensitive plants. Remember to pinpoint your own location when using the local forecast page link by using the Google map embedded on that page to find your location.
Here's a last minute checklist for your home and garden if the TV weather people (or panicky bloggers) tell you upcoming morning low temperatures will be in the mid-20's:
• If it hasn't rained, water plants thoroughly, especially container plants.

• If possible, move sensitive container plants next to a south or west facing wall.

• Cover citrus and other sensitive plants with burlap, row cover fabric or sheets (be sure to keep the sheets dry). Tent plastic sheets on supports over the plants; don't let plastic touch plant leaves. A light bulb placed in such a plant can offer a few degrees of protection. For best protection, sheets should reach all the way to the ground around citrus trees and other freeze-susceptible plants.

• If using an anti-transpirant polymer coating material such as Wilt-Pruf or Cloud Cover, apply at the warmest time of the day, or at least six hours before an expected frost. Read and follow all label directions. If using these products, thoroughly water the plant before applying. In my opinion, use these coatings only as a last resort. Watering plants, moving plants or covering/adding heat to sensitive plants is a more effective strategy.

• Disconnect hoses and drip lines, removing end caps. Lay out straight, off the driveway and out of the path of vehicles. If possible, turn off any exterior water lines at the main; or, thoroughly wrap any exposed pipes and faucets.

  • To prevent broken grass blades, don't walk on a frozen lawn.
• Remove the lowest sprinkler head on each line for drainage.

Protect exposed pipes around wells and pumps

  • To prevent frozen attic pipes, let lukewarm water trickle out of the indoor faucet farthest from the inlet. Also, let faucets with pipes running along an outer, north facing wall trickle during the night.  
• Open cabinet doors to get more heat to the pipes. Close the garage door if water pipes pass through the garage.
• Setting your thermostat nightly at 55 can add needed heat to the attic pipes.

• If leaving the house for a vacation during an expected freeze, turn off the water to the house, and open up the faucet farthest from the inlet. Be sure to turn off your water heater.

  • Cover unprotected faucets and pipes, including any spa or pool equipment.
• To prevent cracking tile, run your pool and spa equipment during the freezing hours. 

• Don't forget about your pets during a prolonged freeze. Bring them indoors at night. Move or replace their drinking water. Break up any frozen water in bird baths. 


• Cover the worm bin, too! Or, move it indoors.