Monday, February 19, 2018

What Should You Do For Your Plants AFTER a 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 several cold 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; the possibility of a frost in Sacramento is anytime between November and late March. The most typical frost period here is December and January. Usually by late February, gardeners thoughts - mistakenly - have turned to planting warm season annuals and putting away the frost cloths for the season. What area gardeners are going through right now is several days 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 do...after a hard freeze, when temperatures are at or below 28 degrees for several consecutive hours? 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. 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 that survived our unusually mild early and mid-winter. This impatiens,  for example 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 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.

Friday, February 16, 2018

Late February Freeze in Sacramento? Yep, It Does Happen.

A late winter surprise for our area: frost and freeze watches are posted for Northern California from President's Day (Feb 19) through Wednesday morning. This is not typical, but not out of the realm of possibility. The usual "frost season" for Sacramento - when there is a 50% or greater possibility of temperatures dipping below 32 degrees - is mid-December through mid-February. However, frosts have been recorded here from the first week of November through the last week of March. It's the "Freeze Warning" issued today by the National Weather Service for Northern California that should have gardeners, homeowners and pet owners concerned.

What is cold? Some definitions:

Frost: temperatures dip to 32 °F (0 °C) for short periods of time. Occurs with fair skies and light winds.
Freeze: temperatures at or below 32 °F
Hard Freeze: temperatures below 28 °F for several hours.

 Fruit-laden citrus trees could be threatened by very cold mornings in the weeks (or days) ahead. Some planning tips for the upcoming cold mornings:

When a frost is forecast:
1. Move potted plants to a warmer spot next to house or under patio cover, especially on south side.

 2. Check that plants are well-watered since dry plants are more susceptible to damage, and moist soil retains heat better than dry soil.

3. Cover plants with a row cover before sunset to capture ground heat radiating upward at night, but remove covers daily if it is sunny and above freezing to allow soil to absorb heat.

4. Add heat by using outdoor lights: hang a 75 watt corded work light or Holiday string lights to the interior of the plant. Use the old C7 or C9 large bulbs, not new LED lights which do not give off heat.

5. Wrap trunks of tender trees if hard freeze is expected, using towels, blankets, rags, or pipe insulation.

6. Harvest ripe citrus fruit. Generally, both green and ripe fruit are damaged below 30 degrees, but there is some variation by species (refer to the chart in UC/ANR Publication 8100, "Frost Protection for Citrus and Other Subtropicals").

7. Winterize your gasoline-powered garden equipment. Gas can go bad and screw up your engines if allowed to overwinter, unused. Drain the tanks or turn off the supply valve and run the engine until it stops. For containerized gas (or gas still in equipment) add a stabilizer. Run the engine for 10 minutes or so to make sure the stabilized gas is thoroughly mixed into the engine.

When a Freeze or Hard Freeze is Forecast (temperatures remain at or below 28 degrees for several hours)

 1. Wrap any exposed plastic water pipes with pipe insulation tubes; use a cover for outdoor faucets. Turn off the water supply to outdoor irrigation faucets, if possible. Allow those faucets to drain.


2. Disconnect garden hoses and lay them out straight...away from driveways!

3. Adjust your pool, spa or pond filtration timers so that they are running when the chance of freezing temperatures is greatest, between two and nine a.m. Moving water is less susceptible to freezing.

4. For dish-shaped fountains: Turn off and let drain to the holding tank below ground. Remove any standing water in the dish.

Frosty the Fuchsia
After a frost:
1. Identify damage: dark brown or black leaves and twigs.

2. Wait to prune out damage until after danger of frost is past, and new growth begins in spring.

3. Make sure the backyard birdbath isn't frozen over in the morning. Daily fresh water for dogs and cats is also a good morning habit.
Tips for Getting Ready for Frost/Freeze Season here:
• Identify cold spots in landscape by monitoring with a thermometer that registers high and low temperatures.
• Identify plants at risk: citrus, succulents, tender perennials, tropical and subtropical plants.
• Have supplies ready: sheets or frost cloths, lights, wraps for trunks, thermometers, stakes or framework to hold covers off foliage.

• Prepare tender plants: avoid fertilizing and pruning after August to minimize tender new growth. 

• Plant insurance: In September and October, take cuttings from frost sensitive perennials; keep cuttings in a sunny, indoor area.
• Monitor weather forecasts and note how low temperatures will be and for how long. 

Pipe Wrap: Cheap Frost Insurance