This photo taken Oct. 30, 2009 shows a boulder, which occupies a prominent spot in the rock garden... 
(AP)
Choosing the right rocks can be as much fun as selecting plants when you're building a rock garden.
Stones create protective wind and sun barriers, and pockets of moisture for small, low-growing alpine flowers. Meanwhile, they are contributing tones and textures all their own.
"The first line in the `Sakuteiki,' the oldest and most respected treatise on how to design a garden in Japan, is about the art of setting stone," said Marc Peter Keane, a landscape architect and educator from Ithaca, N.Y. "Everything follows from there. Rocks are absolutely primary."
Rock placement must be done skillfully so that "even persons knowledgeable about natural formations cannot easily detect the artifice," wrote the late Thomas H. Everett, who was horticulture director and senior curator of education at The New York Botanical Garden, in an account posted on the North American Rock Garden Society Web site.
"Transported rocks must match precisely those of the site and be positioned as though placed by nature."
Availability often determines the kinds of rock you'll use.
"Where choice may be had, one that is porous, rather than such hard, impervious types as granite and schist, is to be preferred," Everett said. "Weathered pieces collected from the surface of the ground and of a character and color that suggest age are likely to be ideal."
More artistic flair is required for fashioning Japanese gardens than alpine ones, Keane said.
"With a Japanese garden, you don't try to create a garden that resembles nature as much as you try to distill it. You create the artwork that brings out some important (site) characteristics."
The rocks should be subdued, not lavish or colorful, said Keane, who designed the stone garden for the recent Kiku exhibition at The New York Botanical Garden. "They should have personalities but not be flamboyant."
It also is essential that Japanese gardens be enclosed in some type of courtyard or space, Keane said. "It's like putting a frame around them. You don't want them out in the landscape. They would be lost."
