Jenna Hertzog dragged her high school friends from a slumber party to a planting party yesterday at a community conservation project near Harford County's municipal landfill in Street.

Helping 200 other volunteers plant 900 seedlings along Deer Creek meant extra credit in biology for the 15-year-old Forest Hill girl and "a totally awesome experience giving back to nature and putting oxygen into the air," she said.

If only she and her friends had dressed for the chilly March weather and the mud. With temperatures barely in the 40s, many volunteers wore wool-lined hiking shoes or sturdy rubber boots. These stylish girls arrived in flip flops that showed off brightly painted toenails.

"Who knew it would be so cold on the first day of spring?" said Mandy Kaminski, 15, of Jarrettsville.

The teens helped mark Harford's sixth annual Arbor Day celebration. In a little less than two hours, volunteers transformed a 3-acre grassy meadow into a neatly aligned stand of trees.

"This land will now be a forest forever," said Michael J. Huneke, a forester with the Maryland Department of the Environment. "We are putting trees back where they will do the most good."

The activity began promptly at 9 a.m. with a brief dedication and the planting of a ceremonial 15-foot red maple. It was Harford's largest community planting to date and involved three types of oak - 100 white, 200 red, and 300 pin oaks - as well as 200 sycamore and 100 green ash, all selected to protect and shade Deer Creek, a drinking water source for many in the county. As they mature, the trees will buffer the creek from the nearby landfill, improve air quality and offer habitat for wildlife.

Huneke condensed planting lessons for the shivering crowd huddled around him. Choose a flag-marked spot in the field and dig deep enough for roots to spread under cover of soil, he said. And hammer a stake next to each seedling.

"Digging deep enough and wide enough and not hitting rocks is the hardest part," Jenna said. "Hammering was a team effort for us."

The steady sounds of shovels hitting earth and hammers tapping wood punctuated an otherwise quiet countryside.

Volunteers covered each staked seedling with a plastic tube to protect it, particularly from pesky deer. Then they double-tied the tube to the stake and topped it with sturdy netting, so as not to entrap small birds.

"I thought there would be mostly parents and environmental people here, but it's mostly kids," said Abby Hannon, 16, of Darlington.

Instilling a love for nature in the young often leads to a lifetime of environmental awareness, said Connie Charitonuk, who accompanied one of several Scout groups.

Hoping to earn his forestry badge, Cub Scout Jonathan Hines, 8, of Forest Hill concentrated on digging until he struck rock and needed his mother's help. Together, they pulled a hefty stone from the ground and continued their task.

Frankie Lopez, 9, of Bel Air cleared away thick clumps of dormant vegetation before planting several sycamores along a narrow stream that flows into Deer Creek.

"Trees are important because they give us oxygen and they clean the water," Frankie said.

Janet Kozak of Jarrettsville had more trouble keeping track of shovels than of the dozen Scouts she was chaperoning.

"You are always trying to keep kids out of the mud," she said. "Here they can pound things and spend a day in the dirt. But they are also learning about doing things for the benefit of everybody."

Fallston resident Lisa Murter and her son James, 9, worked together on what she called "spring renewal." After a morning of planting, the pair planned a trek downtown to the circus.

High school students took charge of quality control, eyeing the field for any tilting stakes. They spoke with classroom authority.

"Trees filter out nutrients and keep them from ruining the bay," said Tom Pigg, 17, of White Hall.

Ben Burke, 11, of Fallston named trees after family members because, he said, "They are all living things and deserve a name."

His mother, Jenifer Burke, coaxed the scattered troops, including Ben and friends, from a post-planting game of jump-the-stream.

"I have never seen these kids so focused," she said. "This is a great project and a good way to teach them good values. They will come back here and see how their trees are growing."

Wet, muddy and with an ever-widening hole in the knee of his jeans, Thomas Harris, 11, of Fallston, felt a sense of accomplishment.

"It is fun to go into the wilderness and save a creek," he said.

mary.gail.hare@baltsun.com