They were selected for their subject matter and to complement the limestone outcroppings that dot the Haltermans' property, she said.
Architectural features like fences and arches can "discipline" the layout of a garden, Halterman said. She added some arches to invite visitors to enter the garden.
Hardscape touches, like dry-laid stone walls and stepping stones, "tend to add a little bit of variety," said Jon Snavely, owner of Snavely's Garden Corner Inc. on Leitersburg Pike.
Decorative pottery and gift items such as sundials, gazing balls and "little inconspicuous pieces, little stone bunnies and mushrooms" tucked into the garden also have become very popular, Snavely said.
"As you wander the garden you stumble upon them," he said.
Ten years ago, concrete fountains were in vogue but now ponds, averaging 300 or 400 gallons but some as big as 900 to 1,200 gallons, filled with goldfish and water lilies, are fashionable, Snavely said.
"Water gardening has just exploded over the last couple of years," he said.
Another growing trend - herb gardens - has sprung from an interest in making healthy, low-fat foods more flavorful.
"Herbs are very big," said Tom Harmon, owner of Phillip's Seeds and Garden Center in Greencastle, Pa.
Halterman said she started dabbling in herbs by planting some mint, basil and thyme.
Container gardening also is becoming more common as people try to bring a touch of nature into urban settings and small living spaces, Halterman said.
Topiary planters, which consist of a clay pot with a metal pole running through its center and a basket on top, are new and quite popular this year, Harmon said.
The planter "adds height to the patio garden," he said.
In terms of what to plant "there are so many choices," Halterman said. She looks for vibrant splashes of color to stand out in her large garden.
"I like things that bloom and smell good," she said. "I love roses, particularly fragrant roses. I tend to plant for the fragrance as much as anything."
Lily of the valley is another personal favorite, Halterman said.
Gardeners often covet the unusual.
Some plants like lantana that grow wild and on a perennial basis in places like the southwestern United States can be grown here as annuals in certain sunny, dry spots, like along hot macadam driveways, Halterman said.
It's always risky to plant flowers here that are native to other parts of the country.
Last year's cool and wet summer hurt the vinca Halterman planted, she said. Vinca is a blooming plant, usually white or pink, that grows 12 to 15 inches tall in hot and dry climates.
Some newly available annuals, such as the white bacopa, which gives creeping ground cover, and the blue scaviola, which stays low and has flowers shaped like half circles, have sold well this spring, Snavely said.
"They are popular because they're different," he said. "A lot of these things people see in their neighbors' gardens and come looking for."
There are some interesting color combinations, such as pink and white and coral shades, now available in geraniums, Harmon said.
Old favorites remain in demand.
Woodview Nursery in Berkeley Springs, W.Va., has had lots of calls for pink dogwoods "because they were so pretty this year," co-owner Laura Smith said.
The cool spring and the continuing threat of frost have delayed the planting of some gardens, Snavely said.
Not only must gardeners wrestle with weather variations but also differing environmental conditions, even within the Tri-State area.
As much as Halterman loves azaleas and rhododendrons they just won't grow in her garden. "I just don't have the right environment for them," she said.
There are many "micro climates," sometimes within the same yard, Halterman said. Shady and protected places may alternate with sunny and exposed spots.
Belonging to a garden club makes experimenting with different plants a lot easier and cheaper, said Halterman, who is second vice president and program chairwoman of Hagerstown's Town and Country Garden Club.
"Many of the plants do their very best when they are dug up every few years and divided," which many garden club members do among themselves, she said.
Halterman also advised visiting places like Longwood Gardens in Pennsylvania for ideas.
Large gardens use repetitive and mass plantings of one variety of flower to make "a big statement," she said.
Three years ago Halterman made her own statement by planting 300 daffodils, she said.
But most of all, she said, gardeners must be willing to take chances and follow their own taste.
"There's a lot of trial and error in gardening," Halterman said. "It's taken me a long time to realize I'm the best expert of what I like."