They pelt innocent children at play, turn front walks into roller rinks, choke gardens and pop like firecrackers off car roofs.
Bushels of acorns are bombarding Maryland this year, a bumper crop that has become a nuisance for city dweller and suburbanite alike. And the state's numerous oak species aren't the only culprits, state agricultural officials say.
Other fruit and nut-bearing trees -- hickories, walnuts, dogwoods and persimmons -- have been showering their seeds on sidewalks, patios and streets. Orchard owners harvested big crops of peaches last summer and are in the midst of a bountiful apple season.
Some agricultural experts say this is merely the boom year of a normal boom-and-bust cycle for acorns, as well as other fruits and nuts. Others say the summer's record heat, drought and insect attacks, both past and present, may be behind the leafy blitzkrieg.
Whatever the cause, the effect on many homeowners has been pure aggravation -- especially in the case of those pesky acorns.
"If I don't rake them and try to mow the lawn, I may get arrested for mass homicide. These would be deadly projectiles coming out of the lawn mower," said Dallas Renner, a McCormick & Co. executive whose home sits among the stately oaks in Original Northwood.
To cope, Mr. Renner and his neighbors have been scooping up the nuts with snow shovels. He recently agreed to pay his 13-year-old daughter, Amy, a penny for every acorn she gathered. A half-hour later, she figures she had filled a couple of buckets containing 3,500 to 4,000 nuts, with plenty more on the ground.
"She said, 'There's $35 worth,' " Mr. Renner recalled. "I said: 'Whoa. Hold on. That's $70 an hour.' At that rate, I wouldn't have been able to put my son through college."
"They're just everywhere," said Amy, who received a painful bump on the head from an acorn a few years ago.
"It's like hearing gunshots at night," said Pam Townsend, media relations coordinator for the University of Maryland's Cooperative Extension Service. "They land on cars, they land on roofs. I'm lucky I haven't been hit with one yet. They're literally carpeting the lawn."
The surplus may have been caused by last summer's record heat and lack of rain, said David L. Clement, coordinator of the home and garden information center of the Cooperative Extension Service.
"Typically in stressful years, such as drought years, there's a response that the trees have where they want to reproduce," he said.
But Christopher Walsh, a horticulture professor at College Park, said he doubted the summer's harsh weather had much effect on the acorn crop.
The fruit and nut trees bloomed and developed their seeds, he said, in April and May of this year "when there was favorable weather and no freezes."
"If you're looking at a heavy crop this year, the roots of that probably go back to 1990," he added.
In the spring of that year, late frosts damaged many of the already scarce blooms, he said, leading to a light crop.
Fruit and nut-producing trees are genetically programmed to produce aheavy "seed set" after a light year, Dr. Walsh and other scientists said. So the trees were primed to produce this year.
Not everyone is unhappy about the surplus. Commercial apple and peach growers were blessed with abundant crops, while grain farmers suffered from the drought.
Even acorns have their fans. After all, the mighty white oak -- known to botanists as Quercus alba -- is the official state tree. And the more white oak acorns, the more white oak saplings.
John Ohler, manager of Martinak State Park near Denton and the person in charge of the state-owned Wye Oak in Wye Mills, said the state's most venerated tree is producing more acorns than it has in five or six years. The 450-year-old Wye Oak is believed to be the largest white oak in the United States.
The Wye Oak's acorns are cultivated at the Buckingham State Nursery near Laurel.