During the past week, we have experienced subfreezing temperatures, below 20 degrees in some parts of the valley. The result: Lots of cold-damaged plants!

What can be done to help those plants recover?

First, determine the extent of the cold injury. On plants with woody stems -- trees, shrubs and vines -- use a knife to peel back some of the bark on stems with frozen leaves. If you find moist, green sapwood just underneath the bark, that stem is still alive. Live stems, even leafless ones, will regenerate leaves when the temperatures warm consistently.

Only cut off stems that have been killed by the cold. These will have sapwood that is dry and brown when you peel back the bark. Cut dead stems all the way back to live wood.

The amount you cut will vary greatly depending on the plant. For instance, lantana may have frozen back to within a few inches of the ground, making it necessary to cut the stems back severely. Other plants, such as citrus, may have little injury to the stems, requiring little or no pruning.

Some plants may have frozen leaves still attached to the stems. For these plants, delay any pruning a few more weeks. The dead leaves provide some insulation to the healthy leaves and stems below. If we do have another cold snap, these dead leaves will hold in some warmth and help protect the plant from further damage.

By mid-March all danger of frost will be behind us and pruning of these plants can commence.

If you are unsure about where to cut, wait until new growth emerges in February or March. This will tell you exactly where the dead parts meet the living. Simply remove everything back to where the new growth is sprouting out.

Flowers and other herbaceous plants injured by the cold need attention without delay. Geraniums, begonias, aloes and other soft-stemmed plants need to have any frozen and wilted stems removed. Cut them off cleanly with a sharp scissors or hand pruners. Remove any old, faded and frozen flowers. Apply a liquid fertilizer to flowers and herbs to speed their recovery.

Wait to fertilize cold-injured trees, shrubs and vines for a few more weeks. Fertilizing now could stimulate new growth that is vulnerable to further cold injury. The exception is citrus; fertilize them in late February to encourage spring flowering and the resulting fruit set. Some of the fruiting buds may already be lost.

Make sure all freeze-damaged plants have adequate moisture. Injured leaves and stems will lose more moisture through their wounds than undamaged ones. Keep the soil moist, but not overly wet. You don't want to waterlog plants!

Using a simple moisture meter available at garden stores will help. Soft stemmed, herbaceous flowers and herbs will be most vulnerable to drying effects of cold damage, so check them often.

Watering also will help eliminate any excess salts that might be in the soil. Salts can cause additional damage to plants over and above the effects of cold. The best way to eliminate excess salt is by leaching them out.

For container plants, simply moisten the soil to dissolve and leach the salts. Wait an hour or so and come back and hand-water the containers until water runs freely out the drainage holes. This will wash the dissolved salts right out the bottom of the pot.

Use the same process for plants in the ground. Water as you normally do, then wait a few hours and water again. Apply lots of water; the excess will push the salts down below the root zone and away from your plants.

If the temperatures continue to dip, it may cause more damage to your plants and crack more pipes. Avoid further inconvenience and expense by following these simple tips:

* Don't sprinkle your lawn when it is freezing to avoid ice formation on sidewalks.

* Water lawns between 9 and 11 a.m. -- but not when it is freezing -- until the frost season passes.

* Wrap exposed pipes with good insulating material, available at hardware stores.

* Wrap tender plants in the landscape and place light bulbs under them.

* Defer watering cactuses until March. They may shrivel, but that's better than being mushy.

* Leave dead fronds on palms until late spring; the added foliage protects the crown.

* Postpone fertilizing ornamental plants until spring.

* Stop watering trees and shrubs until the cold spell passes through.

* Delay pruning trees, shrubs and desert plants until it warms up in February.

* Do not walk on frosted lawns, because footprints will be visible after the thaw.

* Never use clear plastic to cover your plants out in the open. True plastic traps heat during the day, but at night radiates it back out to be 15 degrees colder under the plastic -- enough to kill tender plants.

Look at a frost from another angle. If the frost kills your plants, you are growing unsuited plants. Replace them with those that take the cold better. Otherwise, you continue to gamble with the weather and spend a lot of money after a hard winter.

Many plants look terrible after a deep freeze. It's almost certain they look worse than they really are. Leave the damaged material over the crown until it is spring and then remove it.

Wait a month or so and inspect the twigs of woody plants. Injury doesn't show until later. If the twigs are green they are still alive and if brown they are dead. Watch for new buds and then cut back into healthy wood to stimulate new growth and thicken the plant.

Irrigate a recovering tree, but hold back on the fertilizer. When the weather warms and new shoots appear, give the tree its usual springtime deep irrigation.

ROSE-PRUNING DEMONSTRATION

If you don't understand how to prune roses and want to learn, plan to attend this rose-pruning demonstration from 9 a.m. to 2 p.m. Saturday at the Dick Jackson residence at 1112 Oak Tree Lane. The Las Vegas Valley Rose Society is sponsoring it.

You'll be able to actually prune a rose and see how to properly plant and fertilize them. Also available will be literature for year-round rose care and a list of recommended roses for the valley. For more information, call 646-6048.

Linn Mills writes a gardening column each Thursday. You can reach him at linn.mills@lvspringspreserve.org or at the Gardens at the Springs Preserve at 822-8325.