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After the big freeze, how can you bring back your garden? What about replanting now? What did we learn about frost tolerance?

After the big freeze December's big freeze may be old news by now, but the full extent of the damage it caused to garden plants will be most apparent beginning this month.

The bone-dry, freezing "Yukon Express" that pushed southward from the continental Arctic and sat over much of California for days on end beginning December 21 may have collapsed tender plants such as agapanthus and turned the green foliage of others--including avocados, eugenia, myoporum, California peppers, and Ficus microcarpa nitida--crisp and brown, but this month new life may start mustering beneath the dead stuff. As warm temperatures begin to stimulate new growth, you'll be able to tell exactly which plants are irretrievable and which will survive.

What should you look for? What should you do about the damage? Here is help.

Assessing the extent of the damage

Look for live buds (greenish ones rather than withered brown ones)> the location of the first live bud will tell you how far back the plant has been damaged. If you can't find buds yet, gouge through the bark carefully with your thumbnail> start near the branch tips and work inward at intervals until you discover healthy (greenish or white, wet) plant tissue.

Brown tissue may or may not indicate the plant is drying> some plants whose cambium layers turned brown during the last big freeze (1972) did recover.

On ground covers, look under dead or discolored leaves> below, there may be green pieces with roots attached that survived because the mat of dead foliage functioned as protective mulch. If there's enough green growth below, the plant may recover. If not, you can nurse those living pieces along, then root them.

What to do about the damage

"Procrastination is a virtue after a severe freeze," advises UC David horticulturist Warren Roberts. The longer you wait, the more obvious the extent of the damage will be.

Trees and shrubs. If you can live with all that brown foliage and wait to pick up pruning shears until new growth starts, your plants will probably be better off. Pruning cuts on broad-leafed evergreens and conifers heal better if the plant is actively growing. And old wood or foliage helps protect live tissue below it from further damage until frost danger is past.

One exception: twigs or small branches that are blackened, misshapen, soft, or shriveled are almost certainly dead. Remove and discard them> they could invite botrytis, a fungus that attacks dead or weakened tissue (and can later spread to live tissue) when air is still and moist. Grayish or brown fuzz on damaged leaves or plant parts is a symptom.

After pruning dead growth, wait for plant to leaf out and start growing vigorously before pruning green growth to shape. It may take some time for heavily damaged plants to grow shapely again.

Citrus and avocado branches newly exposed to sun by pruning or leaf loss are subject to sunburn. To prevent it, paint them with white latex paint or wrap them with burlap. If the plant is small enough, cover it with shadecloth.

If bark is slightly split, there is little you can do except leave the crack alone to see if it close (studies have shown that cracks in bark close better when exposed to air than when covered with pruning seal). If the crack is deep enough to collect water, cut an upside-down V at its base to allow water to drain off.

Wide splits in a trunk indicate more serious damage. Knock on the trunk> if it's hollow, the tree has probably had it. Severe vertical cracks could make big tree limbs dangerous hazards. If you spot such cracks, consult an arborist on what to do (look in the yellow pages under Trees).

Perennials. Ones in containers have less chance of survival than ones in the ground, since roots may have frozen. For any perennials, wait at least until late spring (May or June) to see if new growth appears.

Bulbs. Frost may have damaged emerging leaves of tender, fall-planterd bulbs such as freesias and watsonias, but as long as growth buds are undamaged, plants should survive. This month, cut back dead portions of agapanthus or clivia leaves to help prevent crown rot (don't snip crown or emerging leaf buds).

Vines. Those with mature root systems that go semidormant in winter--such as bougainvillea--have a good chance of re-growth from the roots. Wait at least into late summer to see what emerges.

Water now, but wait to fertilize

If you can spare the water, irrigate freeze-damaged landscape plants deeply now, and again later as needed (freezing temperatures dry out plants--a double whammy if those plants are already drought-streesed). Don't water severely damaged soft-stemmed ones like bananas until after new growth starts, since wet soil could cause them to rot.

Wait until new growth starts maturing to begin fertilizing. Scale back amounts in proportion to the amount of foliage lost.

When to give up on--or try to save--a

severely damaged plant

Some plants killed to the ground by frost may have undamaged root systems that will resprout> before removing the plant, wait a year to see if it comes back. On old, established trees, it may take two to three years to know the full extent of damage.

If a budded or grafted plant shows signs of life, make sure the new growth is from the grafted portion, not the rootstock.

If a damaged plant is rare or difficult to replace, and if you can nurse it back to a healthy, shapely form, it's worth the effort to try to save it.

Will replacement plants be available?

Many nursery plants suffered heavy damage in the freeze. Gardeners in northern California especially can expect short supplies into late spring of subtropical tender plants such as bougainvillea and hardenbergia> late-winter bloomers such as Jasminum polyanthum, euryops, and marguerite> and citrus--especially lime and lemon.

In some areas, drought-tolerant perennials such as French lavender (Lavandula dentata) and westringia may also be somewhat limited into late springs or beyond. Prices may be slightly higher.

Summer bedding plants are typically started from seed in early spring> supplies of these--and of native California plants such as ceanothus, which were mostly undamaged--should be unaffected.

Should you buy hardier plants?

It would be hasty to judge a plant's suitability for your climate by how it performed in an extreme freeze like this one. Kathy Musial, botanist at the Huntington Botanical Gardens in Pasadena, advises: "Look at its hardiness in your average low temperatures."

Many plants--especially drough-resistant ones from Mediterranean climates--have virtues that outweigh their inability to withstand record low temperatures once or twice a century. And they may live out their lifetimes quite happily before another big freeze comes.

Should you replant now, in a dry year?

Recently set-out plants--even drought-tolerant ones--need water to get established. Where water supplies are limited, you may want to wait until fall to do major replanting, and use the water you have to help bring back and salvageable freeze-damaged plants.
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Title Annotation:includes related article on collecting freeze data on plants
Date:Mar 1, 1991
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