Peach trees

Peach trees are already in bloom at Larriland Farms. (Amy Davis, Baltimore Sun / March 21, 2012)

Just as they do every April, the fruit orchards at Larriland Farm have donned their spring finery.

The plum trees at the pick-your-own place in western Howard County sport brilliant white blossoms, while the peach trees are decked out in bright pink.

Thing is, it's still March.

Spring came early to Maryland, thanks to a run of unusually warm weather that awakened flowers, trees, birds and bees weeks ahead of schedule across much of the eastern United States.

Larriland's fruit trees are flowering about a month earlier than usual, according to Lynn Moore, president of the family-run fruit and produce farm in Woodbine. Farther west in Thurmont, the owner of Catoctin Mountain Orchards says his trees are blooming three weeks early. Wine-makers across the state report their grape vines are starting to bud out two to five weeks sooner than normal.

That may be unusually early, but spring seems to be getting a jump on itself more and more. Climate experts call it "season creep," with winters getting warmer, and growing seasons longer, on average.

"It does seem like springs are getting weirder and wilder around the nation," said Jake Weltzin, a biologist with theU.S. Geological Surveyand director of the National Phenology Network, which is tracking the influence of climate on plants, animals and landscapes. "You see a lot of variation from year to year, but you see this trend toward earlier springs."

The trend doesn't appear to be global, but in temperate regions researchers have found clear shifts over decades in the timing of first appearances of flowers and leaves.

Scientists reported last year in the Journal of Climate, for instance, that tallies kept since 1950 in western North America show buds and blooms are showing up 1.5 days earlier, on average, per decade.

In the Northeast, other scientists working from detailed records kept by 19th-century naturalist Henry David Thoreau found that some species he tracked in eastern Massachusetts 150 years ago now flower up to 10 days sooner.

And closer to home, Smithsonian scientists determined over a decade ago that 89 of 100 native plants in the Washington-Baltimore area were blooming about 4.5 days earlier than they did in 1970 — and that Washington's famous cherry blossoms were popping out a week sooner.

Long-term weather shifts can last years or even decades. And recent research suggests that some of the advance in spring flowering may be attributable to the "urban heat island effect," where paved-over areas generally are warmer than the countryside. A University of Maryland scientist and colleagues noted that growing seasons are longer within 20 miles of cities in the Mid-Atlantic region.

Most climate-change models predict a 3-to 8-degree-Fahrenheit increase in average annual temperatures by the end of the century. But some scientists say a warming planet may be contributing to weather extremes seen lately, including early onsets of spring.

"Even though you can't say any particular year that 'this is due to climate change,' the fact you have these really unusual conditions suggests it would not be that unusual without the increase in temperatures that the climate is causing," said Donald F. Boesch, president of the University of Maryland Center for Environmental Science, who helped write a National Academy of Sciences report series called "America's Climate Choices."

While many may be inclined not to worry about the future and simply to relish the extra balmy weather, it produces anxiety for those who make a living raising fruit. Fruit and nut growing was a $19.4 million business in Maryland in 2007, the latest year for which the U.S Department of Agriculture has census data.

"It puts you more at risk," said Moore, whose farm produces berries, cherries, apples and a variety of other produce. The flowers could wither if a frost hits, and fruit won't form. It's happened before — when warm spells triggered early peach blossoms a couple times in the 1980s and '90s, she said, she lost practically the entire crop to frost.

"We all are concerned," said Robert Black, owner of Catoctin Mountain Orchards. "We're just so far away from being out of the frost period."

The National Weather Service in Sterling, Va., acknowledged Thursday what's obvious to anyone who's stepped outside — the region's "incredibly warm" temperatures have triggered an early growing season for most of the Baltimore-Washington area.

Still, the forecasters warned that blooming fruit trees are vulnerable because temperatures typically dip into the mid-30s and below for at least a few nights in April. And there was even a frost in the Shenandoah Valley in May 2010.

That worries grape growers and wine makers as well. After an extremely mild winter in mountainous Garrett County, Paul Roberts of Deep Creek Cellars said that it looks like his fields may experience "bud break," when leaves start emerging from the vines, any day now. That's the third year in a row of early growth, and the earliest he's seen in 15 years of cultivation there.