PHILADELPHIA — Fashionistas in the garden like those great big blooms with petals thick as petticoats, but there's another way to go: rock-garden plants.
Their flowers are small, subtle, and every bit as beautiful as their hefty peers, as Ann Rosenberg of Bryn Mawr, Pa., discovered around 1985. On a trip to England that year, she delighted in some small penstemons, which sparked an interest in other plants commonly used in rock gardens.
"They're so cute!" she said.
They're usually less than 4 inches tall, maybe as tall as 12 inches if you count things like dwarf conifers, another popular rock-garden feature. Shaped like buns, mats and cushions, these tiny plants are tucked into crevices and fissures, where there might be little soil, their diminutive stature intended to show off the color, form, size and texture of the rocks.
Their flowers can be very colorful and disproportionately large, and you can squeeze a lot of them into a small space, something all gardeners seem genetically wired to do.
That "small space" can be a container, a trough or a raised bed, a bonsai dish, antique sink or perennial patch. Fill can be a mix of topsoil and sand, or gravel, or weathered rock fragments known as scree. Rosenberg doesn't have a rock garden per se; she uses home-grown rock-garden plants to create a dreamy woodland behind her house. There, clouds of soft-blue forget-me-nots and ultraviolet wildflowers known as bluets (or Quaker ladies) line the gently curved paths. They brighten a cloudy day like minuscule sparklers, set against the tart spring-green of everything else.
Rosenberg also grows primula and armeria, daphne, dianthus, gentian, and mini-hosta and mini-narcissus in there, and in rough troughs made by her husband.
Gentiana acaulis is a favorite. It's a kingfisher-blue gentian, 4 inches tall, an Alpine native with solitary trumpet-flowers measuring 2½ inches long. Imagine a hillside dotted with these.
Which recalls this advice: Whatever form it takes, a rock garden should look natural, as if this craggy scene has been growing undisturbed for some time.
Pat Valentine puts it simply. "A rock garden consists of plants planted next to rocks, but it's not just that. There's an extreme art to it," he said. "You try to copy what's growing on the side of a mountain."
Valentine owns Valentine Gardens, a specialty nursery in Coatesville, Pa., that propagates and sells unusual plants for rock, water, sun and shade gardens. He's built a figure-eight rock garden in the sunny yard to show visitors how it's done, at least in this country.
But when asked to explain the attraction of these miniature landscapes of deep-rooted plants, Valentine's as mushy as Rosenberg.
"They're so cute," he said.
"Touring" this garden is nothing like a spin through a blizzard of perennials. We stand at the edge, bend over, look closely. We move 6 inches to the right, bend over, look closely. It takes nearly an hour to make our way around the figure eight, which is 22 feet long and 10 to 12 feet wide, with a pitcher's mound in the middle.
"It's a real neat facet of g ardening," said Valentine, who's made a living in the nursery and landscape trade for 47 years. He bought this nursery with partner Patricia Schrieber in 2001.
The plants in his rock garden creep. They mound. They poke out of cracks and hug the ground. Valentine finds them quirky and romantic and said grandly that working with them can involve "major character development."
There's an alpine baby's breath, really just a green cushion with pinhead-buds. There are dwarf conifers and rugs of thyme and sedum inching around mounds of a moss phlox called Crackerjack and Little Jock, a frilly dianthus.
Everywhere, you see sempervivum, or "hens and chicks." There's no mistaking those chubby leaves of pink or green and those distinctive cobweb hairdos. And get a load of the red or black tips. They resemble sharpened fingernails.
The "chicks" are the rosette-shaped offspring that grow in a ring around the "hen" or mother plant. As some indication that, even in a rock garden, the action is hot and heavy, the "chicks" naturally "fill the vacancies," as Valentine describes the holes left after the mothers flower and die.
He uses feather rock, lichen-covered limestone, jagged lava rock, granite street stone and the occasional piece of quartz.
The rock-garden concept is great for urban gardeners and others without much space.