If you want to include plants in your rock garden, then your first task is to select the appropriate plants for your area—and for yourself. Your USDA zone is likely to be the single most important factor in your decision.
This information tells you what sort of plants can survive your coldest days. In particular, you should probably choose a plant for “any zone’ if you live in an especially cold area. Other areas are usually close enough for what you need.
Something else you should consider is the level of sunlight you receive. Putting a plant which needs a bunch of sunlight won’t work if all it gets is shade. Gardening is too much effort if your plants are just going to die. Lastly, be careful regarding poisonous plants. You probably want to avoid them, since they may have unpleasant results on your family and your garden.
Some plants can survive through the year in any zone, which makes them great for nearly any garden. This type includes green carpet and baskets of gold. The basket of gold plant needs about three hours of sun to do well, but the green carpet plant needs hardly any sun to survive. There are some plants that need a lot of sunlight; these include stonecress, dwarf yarrow, rock jasmine, rockcress, catsfoot, alpine aster, sea pink, ice plant, mountain avens, whitlow grass, sulfur flower, spurge and alpine poppy (both of which are poisonous), evergreen candytuft, dwarf baby’s breath, oregano (as an herb, it’s also very good for cooking), soapwort, speedwell, and pasque flower.
If you receive about three hours of sunlight each day, then your options include pinwheel, sheep bur, carpet bugle, aubretia, windflower and alpine columbine (both of which are poisonous), creeping bell-flower, alpine pinks, snow in the summer, shooting star, fleabane, hens and chicks, Cranesbill, coral bells, trumpet gentian, Lewisia, lithodora, phlox, Penstemon, Northern Jacobs Ladder, saxifrage, primrose, cushion pink, stone crop, woolly thyme, blue eyed grass, and snowball.
If you don’t receive any good sunlight during the day, you still have some options available—such as particular kinds of Northern Jacobs Ladder, hens and chicks, and primrose, as well as all kinds of rockery orchid. If you prefer the plants in your rock garden to be taller, you can use windflower, pinwheel, shooting star, alpine columbine, sulfur flower, evergreen candytuft, lewisia, and coral bells.
But if you prefer shorter plants, then creeping bell-flower, trumpet gentian, hens and chicks, sheep bur, dwarf baby’s breath, rockery orchid, green carpet, woolly thyme, and Stonecrop are perfect for you.
But regardless of your region or your climate, there are probably some plants that would work great in your own rock garden. And so long as you take care to select only plants which fit your capacities for sunlight, water, and temperature levels, then you’ll probably have a rock garden, maintenance-free, just need to maintain it regularly with a manual mower or other mowers, and all the time for you and your neighbors to enjoy. And if you take a little extra time on your designs, you can match colors with your plants to turn heads even better with your display.