When we speak of listing "rock garden plants," we are not, of course, referring to a botanical classification. There are all kinds of possible entries for such a list, depending on your conditions and aesthetic goals. But that does not mean that your plant selection can be willy-nilly.
Nor does it mean that some specimens haven't been favored as classic rock garden plants, traditionally. These rockery classics tend to share certain characteristics, including:
- Drought resistance
- A need for good drainage
- A compact growth habit (proportionately)
As said above, to get plant selection right, it is critical to be mindful of your conditions, to match your rock garden plants to those conditions, and to group specimens with similar growing requirements together. Thus, if your conditions are the traditional full-sun with fast-draining soil, select rock garden plants that want a lot of sun and sharp drainage. And if your planting area is large enough that it contains multiple conditions -- perhaps a few pockets where the soil retains a bit more moisture -- group your selections accordingly (e.g., reserving those pockets with more retentive soil for specimens that want a little more water).
The list of rock garden plants that follows is geared to full-sun perennials. If the location in question is shaded, you may wish to browse my list of plants for shady areas. I have grouped the entries on my list according to size. The bigger your area, the bigger can be the vegetation, as long as you extend this sense of proportion to the rocks (so that they do not become "lost").
- Small Rock Garden Plants
- Yellow alyssum
- Purple ice plant
- Angelina stonecrop
- Hens and chicks
- Creeping thyme
- Blue fescue
- Creeping phlox
- Reticulated iris
- Wood spurge
- Medium-Size Rock Garden Plants
- Moonbeam coreopsis
- Autumn Joy sedum
- Royal Candles speedwell
- Blue Rug juniper
- Shasta daisy
- Black-eyed susan
- Perennial salvias
- Six Hills Giant catmint
If you have just a small space in which to landscape, then it will probably make the most sense for you to select small rock garden plants. Luckily, the choices here are legion. There are many small rock garden plants whose delicate beauty is quite exquisite, such as purple ice plant (click picture at left for a larger image).
Keep in mind that features such as small stone retaining walls can also house rock garden plants. Small specimens such as hens and chicks are indispensable for planting the crevices in dry-wall stone walls. Meanwhile, I think bright-flowered, cascading beauties such as yellow alyssum are ideal for planting on top of walls, allowing them to spill down the sides. The effect of these plantings is to soften the otherwise rigid lines of the wall.
Some small rock garden plants are creepers, such as dragon's blood stonecrop. But certain creeping plants come with some serious baggage. Ajuga, for example, is invasive and, if you still decide to grow it, I recommend removing stray runners promptly.
Sometimes, like Goldilocks in the fairy tale, you're looking for that happy medium. You do not want anything too small, but something too big will not work, either. So in this section I present some examples of medium-size rock garden plants.
One of my favorites is columbine (picture at left). I find the shape of its flowers fascinating. But there are plenty of other possibilities, among them purple coneflower, which, like columbine, is a North American wildflower. If you'd like to mix things up a bit and inject some silver leaves, try Lychnis coronaria (but keep an eye on it if you do not wish it to spread).
The next best thing to having the Hanging Gardens of Babylon in your yard is landscaping a steep slope with boulders and eye-catching rock garden plants. This is an example of turning what could be a landscaping nuisance into a highlight. But tiny specimens dotting a gigantic hillside will not show up very well (unless massed for a blanket-like effect, as we sometimes see on hillsides with creeping phlox), so you'll have to turn to the big boys in these situations. Just remember that the idea is to keep everything in proportion, which is why I used the word "boulders" rather than "rocks."
One tough specimen of suitable size and useful in such conditions is Rosa rugosa. Another robust customer is rockspray cotoneaster. An evergreen selection and a nice choice for a Japanese theme is mugo pine.
Russian sage (picture at left) and lamb's ear are more delicate-looking than the other members of this section, but they still offer some height where it is needed. In the latter case, however, the height is in the flower stalk; in fact, if you want to use lamb's ear as a smaller specimen, just remove the flower stalk when it appears and treat it as a foliage plant.