Whether you're confronted with a boulder-strewn hillside or a stone-littered front yard, rock gardens solve seemingly impossible growing challenges. In fact, plants thrive in the sandy, shallow and infertile soil of the typical rock garden. Before ordering your seeds, however, make sure the plants correspond to your particular growing conditions. No matter the climate, however, most rock gardens present too inhospitable an environment for nurturing seeds. It's best to start plants indoors and transplant the seedlings by scraping away the top soil and inserting the plants among the rocks.
Herbs, many of which famously adapt to the rocky, sandy soils of the Mediterranean regions, also do well in the relatively non-fertile soils of the typical rock garden. Keep in mind that soil perched just a few feet higher on a slope will be significantly dryer than soil at the bottom of a hill, so arrange your herbs into the "microclimes" they love best.
Lavender and rosemary appreciate dry, crumbly conditions, while mint and lady's mantle like the slightly moister soil available toward the bottom. Among the dozens of suitable rock garden herbs available to be grown from seed are basil, salad burnet, calendula, chamomile, catmint, chives, costmary, dittany, garlic chives, oregano, sage, horehound, hyssop, lady's mantle, lavender, mint, parsley, pennyroyal, rosemary, southernwood, scented geranium, marjoram and thyme.
Flowering perennials known to thrive in rock and alpine gardens include yarrow, common thrift, snow-in-summer, pinks (also known as dianthus), blanketflower, alpine aster, "blanket of gold," heather, heath, hardy geranium, evening primrose, alpine poppies, columbines, fringed bleeding heart, shooting star, phlox, foamflower and violet.
Trees and Shrubs
Many trees and shrubs can be grown from seed, but be aware that it may take two or more years before they can be transplanted into their ultimate location. Start seeds indoors, and transplant seedlings into a "nursery bed" outdoors for the first year or two, giving them winter protection as needed.
Dwarf or naturally small varieties do best in rock gardens, including barberry, cotoneaster, dwarf juniper, pine, fir, yew and arborvitae, Hinoki false cypress, lowbrush blueberry, dwarf rhododendron and azaleas.
Because stones and boulders retain so much heat, rock gardens give you the perfect opportunity to try plants that normally wouldn't over-winter in your climate. Grow succulents such as hens and chickens, prickly pear cactus, yellow stonecrop and euphorbia.
While not technically seeds, bulbs are the easiest starting point for several kinds of flowers. For rock gardens, the smaller bulb plants work best. They include jonquils, crocus, trout lily and Neapolitan cyclamen.
Ferns and Foliage
Several varieties of ferns and hostas do well in shadier, alpine-type rock gardens. Ferns grow from spores rather than seeds, and take a bit more horticultural knowledge than the amateur gardener possesses, but it is possible to learn through research. Hostas sprout relatively easily from seed, but like shrubs, take at least a year to become hardy enough to transplant. They are also notorious for not growing true to their parents, so either keep this in mind when harvesting your own seeds, or buy seeds from a reputable grower.