Balmy weather tempts plants into early bloom Horticulturists fear damage from frost

December 14, 1991|By Douglas Birch

It's past their bedtime, and growing things need their rest.

But this fall, balmy temperatures have kept some of Maryland's flowering plants wide awake and sprouting buds and blooms out of season.

And garden specialists warn that a sudden nose-dive by the thermometer, plus the continuing dearth of rain, could mean that gardens will not blaze quite as brilliantly this spring.

"Potentially what happens with a lot of the flowering shrubs, for example, is they'll come completely out of dormancy and they'll lose a lot of their cold tolerance," said Scott M. Aker, the state extension service's urban agriculture agent for Howard County.

If so, and there is a sudden, severe cold spell, "the flower display will be ruined next spring," he said.

The prospect of a drab spring has some gardeners in a sweat. But not Pat Scott of Dayton, in Howard County, who holds weather wimps in contempt.

"It's not any real big issue," she said. Early blooms are "not particularly harmful to the plant. If you had a long spell, you may see some bulbs forcing themselves up. But that's not really harmful."

Maryland's weather careens between icy cold and mild in the winter, she noted, because it's in a geographic "no man's land." "We're neither north nor are we south, and we get kind of a mix," she said.

Sure roller-coastering temperatures threaten a plant's complexion and next spring's set of flowers, she said. But not the life of the plant. And ornamental shrubs don't have to suffer from drought -- gardeners can simply water them through the winter.

Still, temperatures in the Baltimore area -- which have been almost three degrees warmer than average over the past 11 months -- have some plants confused.

Forsythias, azaleas and roses have developed a few buds. Cherry trees around Columbia Mall have bloomed a bit. Some tulips, daffodils and crocuses near Towson are peeking out of their winter bunkers. Even an occasional dandelion has turned up.

Some plants need a long period of cold "to put them to sleep" and stop growing during the winter, said Dr. David L. Clement, coordinator of home and garden information for the state's Cooperative Extension Service. "We haven't really had a long enough cold period to put them into a deep dormancy, so they're trying to grow again," he said.

"The primary effect of warm temperatures this time of year is to decrease hardiness in a lot of plants, because hardiness is something that plants develop over time as the plants gradually get cooler," said Mr. Aker. "Within a couple of days, if we see temperatures down around eight degrees above or 10 above after the week we've had now, then we'll definitely see some damage to plants," he predicted.

The latest stretch of warm weather is expected to end this afternoon. Overnight lows drop into the 20s by tomorrow, forecasters say -- probably not cold enough to cause problems. But the cold season, or what is masquerading as the cold season,has only just begun.

Victims of a drastic shift in temperatures would display "winter burn," Mr. Aker said -- meaning their leaves would die around the margins. The most vulnerable plants are broad-leafed evergreens, such as camellias and holly.

Some cherry and apple trees bloomed earlier this fall. But Mr. Aker blamed that on the lack of rain, not the surplus of heat.

So far this year, rainfall for the Baltimore area is about 30 percent below normal, according to National Weather Service figures.

Mr. Aker said that if the drought gets much worse, and plants feel in mortal peril, then next spring's bloom could actually improve.

"Many plants, when they sense they're about to die, will as a last ditch effort try to put out a lot of bloom, to reproduce before they die," he said. "So a heavy flowering should not be taken as a sign of health, necessarily."

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