Rock Gardening for Beginners

Callirhoe involucrata
Callirhoe involucrata is a charming, heat tolerant summer bloomer for the rock garden.

Rock garden plants have an elfin, seductive charm all their own. Hailing from windswept, mist-shrouded summits, rocky slopes, craggy coastlines, and other picturesque and often challenging habitats, they somehow embody the mystery and majesty of their native haunts. Make their acquaintance and you will almost certainly yield to their spell.

Clematis fremontii
Clematis fremontii is an unusual, attractive species fit for rocky garden spaces.

Just about any garden can accommodate at least a few of these beguiling rock-dwellers. Moreover, their diminutive size and their preference for rocky niches make them some of the best subjects for space-challenged gardens. Tucked into a patio wall, or nestled in a clay pot, or associating in an alpine trough, they excel at bringing character and ornament to garden nooks and crannies. They even work well in urban settings.

Growing Rock Garden Plants

Getting them to grow happily in a domesticated habitat is another matter. To simulate a boulder-strewn mountaintop can be a bit of a trick if you garden in central Manhattan. Fortunately, many popular rock garden plants are relatively undemanding, taking well to most well-drained soils (although varying in other requirements such as exposure and soil acidity). As for the fussier types, most do well in humus-rich, nutrient-poor, gritty soil that stays moist in spring and cool and relatively dry in summer. A little Fafard® Sphagnum Peat Moss makes a fine amendment for gritty soils in need of added organic matter. Of course, almost all rock garden plants do best (and look best) in the company of rocks, which buffer their roots from heat and their stems from cold and dampness.

Building a Rock Garden

If you garden in coastal or upland New England or the Rockies, your unamended back yard may make the perfect rock garden habitat. In less craggy regions, however, some modifications may be necessary. To create a large rock garden habitat on well-drained but stone-free soil, bury large flattish rocks at a slight upward angle with their tips exposed. Place the rocks in such a way that they suggest the edges of an underlying rock ledge. Surface groupings of a few rounded boulders also work well.

Sisyrinchium idahoense flower
Sisyrinchium idahoense offers delicate starry flowers over grassy foliage.

Build small rock gardens from scratch by burying rocks in mounded growing medium, or by sandwiching the growing medium between stone retaining walls. A mixture of equal parts topsoil, coarse sand or grit (such as calcined clay), and Fafard compost makes an excellent medium for many rock garden subjects. The same mix can be used to create growing pockets in existing stone walls. For a micro-garden that can reside on your patio or at your doorstep, buy or make an alpine trough – a tub-shaped planter specially designed for alpine plants (see how to build and plant one at this link).

Easy Rock Garden Plants

Among the seven best plants for beginning rock gardeners (or any rock gardeners, for that matter) are:
1. Fan columbine (Aquilegia flabellata) and other dwarf members of the genus Aquilegia. Hummingbirds adore them.
2. Campanulas, including Carpathian harebell (Camanula carpatica) and Dalmatian bellfower (C. portenschlagiana). Both do well in full to partial sun and any not-too-soggy soil.

Dianthus gratianapolitanus 'Grandiflorus'
Dianthus gratianapolitanus ‘Grandiflorus’ is an easy charmer for early summer rock gardens. (image by Jessie Keith)

3. Cheddar pink (Dianthus gratianopolitanus), alpine pink (D. alpinus), and others of the Dianthus tribe, featuring grassy leaves and fringed, spicy-scented flowers. Most prefer full sun and alkaline soil.
4. Beardtongues such as hairy beardtongue (Penstemon hirsutus) and pine-leaf beardtongue (P. pinifolius). Hummingbird favorites, they thrive in sun, acid soil, and low humidity.
5. Lewisia cotyledon and its many beautiful selections and hybrids. This native of Northwest mountains loves cool, gritty, lime-free soil, and an east- or north-facing slope.
6. Phlox stolonifera, P. divaricata, and other low-growing phlox. The two mentioned here are best in partial shade.
7. One of the most beautiful Eastern woodland natives, bloodroot (Sanguinaria canadensis), which occurs in nature in shady, rocky habitats. Double-flowered forms (such as ‘Multiplex) are especially beautiful, and relatively long-blooming.

Sanguinaria canadensis 'Multiplex'
Sanguinaria canadensis ‘Multiplex’ is a double-flowered ephemeral ideal for spring rockeries.