Beauty thrives in rock garden

There are all sorts of practical reasons to try your hand at rock gardening. Such a garden can flourish without mulch, mowing or pesticides and needs little feeding and weeding. It's an ideal horticultural art form for people who travel a lot or don't want to spend the whole weekend playing in the dirt. And because the rock garden is free-draining and mulched with gravel, it is inherently equipped to handle the gully washers we saw this week.

But those attributes are not the reason I am growing fonder of this form of gardening.

No, it's the plants. Consider the beauties that thrive in an arid setting. Pinks -- so much lovelier than their ungainly kin, carnations -- are now a thicket of stems capped with starlike blossoms in pink, white and red. After flowering they revert to cushions of blue-gray, huddled against the drying winds.

The more you probe this rocky world the more obscure and captivating is the flora. In late spring, plants are transformed into bloom. Take the Delosperma nubigenum, a creature with low, tiny sausagelike leaves and now topped with bright yellow daisies. I am smitten by another composite now in flower, the Atlas daisy, Anacyclus depressus. From flat, feathery leaves, stalks appear in the spring to bear daisies with white petals around a yellow boss. The underside of the petals is striped red, and the effect is mesmerizing.

Here's another rare beauty doing its thing this week: Asphodelus albus. It looks like a small but soft yucca, with a central flower spike whose pink flowers open and close daily, turning from tubes to stars after the sun passes its zenith. It is a lily relative from the Mediterranean.

Small is pretty

Most of these plants are small. Indeed a big plant would look unnatural in a rock garden setting; that's why rock garden fans stick in slow-growing dwarf conifers as a foil to the perennial flowers and diminutive ground covers such as Elfin thyme and various stonecrops.

These plants have evolved as deep-rooted compact plants, reaching down for scant water and huddled against the constant wind of their native arid and mountainous habitats. What they can't stand is clay soil and wood mulches; the crowns would rot in a heartbeat, especially in winter.

Thus, you must create something of a moonscape for them. The beauty of these otherworldly gardens is that you can do it on a tiny scale, in homemade troughs or around your entire property.

Holly Downen, a seasonal gardener at Green Spring Gardens near Annandale, Va., recently made two troughs to replace old ones that were crumbling. Essentially, you take a form of some kind; she uses foam sheeting nailed together, but a cheap plastic basin would work. She then takes Portland cement, peat moss and perlite and mixes them dry. Then she adds water, mixes them again and adds nylon fibers to reinforce the mix. The concoction is poured into the mold, where the sides are formed by hand and allowed to set. The trough is wrapped in plastic to cure slowly over three weeks and then left for two more weeks for most of the lime to leach out.

Downen puts a base of gravel in the troughs, which must have drainage holes, and builds a growing mix of grit, sand, potting mix and more perlite. Young plants are watered to get established, but then thrive on neglect. She plants the troughs with dwarf conifers, stonecrops, sempervivums, thyme species and scutellarias.

Her troughs are about 18 inches by 30 inches and 8 inches deep, large enough for an entire microcosmic garden.

Creating a gravel garden

Michael Bordelon is living proof that you can turn your yard into a trough garden. A plant collections manager at the Smithsonian Institution's botany greenhouse in Suitland, Md., he was fed up with landscape crews kicking up stones and breaking windows when they mowed the grass around the greenhouse.

He fixed the problem by removing the turf, creating berms of compost and smothering two sides of the greenhouse with more than 40 tons of river bank gravel. The traditional delineation between path and bed doesn't really exist here, so plants can grow and retreat through the year without creating the obvious holes in a traditional garden bed of soil and mulch. An orange-tan aggregate is his mulch.

There is whimsy here. A berm is crowned by a Japanese garden juniper that has been trained to look like an octopus (complete with eyeballs), and other common plants grow alongside the rock garden oddities. A few shrubs and trees provide structure, including a Japanese apricot and several redbud trees, which one thinks of as wanting a forest leaf mulch but are clearly happy tapping into what's below the gravel.