Same with gardening.
The big idea here is to save water however you can. And though rock gardeners and a municipal water department may seem odd flower-bedfellows, they're of one mind: An easy way to conserve is to plant stuff that doesn't need a lot of water in the first place.
Sedum and Delosperma cooperi, or hardy ice plant, for example. They're perfect together, both tough succulents that tolerate drought by storing water in their chubby leaves, stems and roots.
"They're very eco-friendly," says Walt Cullerton of Pineville, Bucks County, part of the North American Rock Garden Society's Delaware Valley chapter. "They like to live the way nature set them up - in the mountains, with cold winds and limited moisture, in very harsh conditions."
Such conditions prepare them for taking root on an energy-saving green roof, like the one the Water Department built at the Flower Show. Or in a city or suburban garden, like the one in the Rock Garden Society's exhibit.
Rock gardeners love low-growing or miniature plants, mostly perennials, such as ajuga, sempervivum (hens 'n chicks), saxifrage, woodland anemone, hellebore and dwarf shrubs and conifers.
"The true rock gardener gets really excited," Cullerton muses, "when he sees a half-inch bloom on a one-inch plant somewhere above the tree line in Colorado or Afghanistan, growing out of rocks.
"They're very serious people," he says.
Dick van Duzer of Pipersville uses spring bulbs in his rock garden, things like tiny snowdrops, miniature iris and narcissus. He's a fan, too, of native heuchera and hardy cyclamen, excellent water-conserving groundcovers for any garden.
And that's the point, partly, says the Water Department's Arthur Holst, who coordinated its green-roof exhibit at the Flower Show.
