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Twelve days ago,
coastal gardeners awoke to find many of their garden plants
withered and burned after one of the coldest nights in recent
memory. Frost damage to tender plants was obvious as weather
stations hit record lows: Costa Mesa went to 29 degrees. Upper
Newport Bay, western portions of Irvine and downtown Laguna
Beach dropped to 30 degrees. Bolsa Chica, Talbert Village in
Huntington Beach and UCI recorded 31 degrees. Even Balboa
Island, probably the warmest spot in the county, dipped to 36
degrees.
But it's not necessarily the end for frost-frizzled plants.
Phones were ringing off the hook last week at Roger's Gardens
and other nurseries for advice on what to do. Gardeners were
seeking advice on how to save tender hibiscus, bougainvillea,
lantana, ficus, cape honeysuckle, geraniums and others.
The best advice, as hard as it may be to accept, is to do
nothing at all. Wait until early spring to see what the real
damage might be. There is nothing you can do to salvage
cold-damaged plants other than to wait and see if they recover.
Pruning now would expose still-healthy plant tissue to the cold
and stimulate new, tender growth that's even more susceptible to
injury than the already-damaged older growth. Now is not the
time to prune damaged plants or fertilize them; wait until new
growth emerges in the spring. Fertilizing would promote new
growth, which would be tender and subject to future frost
damage.
Along the coast of Orange County, frost is a rare occurrence,
blamed for more damage than it causes. Orange County is a land
of microclimates, one gardener's low temperature is not the same
as another's a few doors away. Even in your own yard, changes in
elevation, canopy and exposure will affect the temperature
around tender plants. The same plant, growing in different
locations in a garden will react quite differently to what
appears to be the same temperatures. In fact, the temperatures
may be quite different just a few feet away.
To understand frost, remember that cold air sinks and warm air
rises. During the day, energy from the sun warms the soil. At
night, this heat rises back into the air. On cloudy nights, heat
stored in the soil rises to the clouds and is reflected back to
the earth's surface. High humidity moderates these temperature
changes, while low humidity, like we had last week, will
accelerate these changes.
As warm air rises, colder air takes its place. Temperatures near
the ground are often five degrees cooler than the temperature
just two or three feet higher. When you see a "frosty" lawn in
the morning you are seeing this effect of elevation on
temperature. If, on a cold night, we are fortunate to have a
gentle wind it will mix the rising warm air with the sinking
cool air, resulting in warmer temperatures. During winter, our
air is often dry, the air still, and clouds absent. These are
the conditions that pose the greatest danger of frost damage to
plants.
Easy strategies that will keep plants warmer include moving
potted plants closer to the house or under a tree with a large
canopy. Stringing Christmas tree lights (the big-bulb type)
around a plant will generate heat, especially if a plastic sheet
is placed on top. For plants that can't be moved, putting a
couple of layers of old bedsheets over them will add a few
degrees.
Unfortunately, the cold nights of last week may have caught you
by surprise, and it may be too late for many plants. If you
noticed leaves hopelessly wilted or turning black, that's a sure
sign that it took a hit.
Under no circumstances should the dead portions be pruned back
until consistent warm weather returns in the spring. Pruning now
would expose still-healthy parts of the plant to the cold and
also stimulate new, tender growth, which is even more
susceptible to injury. Those ugly, frost-damaged leaves and
stems will help trap warm air and protect dormant buds that will
sprout once growth resumes. In a couple of months, or sooner,
the frost danger will have passed and new growth will begin. At
this time, trim off the damaged leaves and cut back any dead
tips.
As awful as it may look and in spite of wanting to do something,
you'll be better off leaving frosted plants as they are. You'll
be surprised that most of those burned plants or scraggly twigs
are still alive. All is not lost. Spring will be here soon.
ASK RON
My camellia has had buds for weeks, but it is still not
blooming? How can I get it to flower?
MICHELLE
Newport Beach
Don't worry, nothing's wrong. Camellia japonica flower buds
begin developing in about September or October in Orange County
and are often obvious on the branches for months before they
finally open. It is critical that you do not fertilize now. A
shot of nitrogen right now could cause the plant to drop these
buds to the ground. Just be patient — they'll open when they're
ready.
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