
 The Natural Garden, Inc.
The Nursery Specializing in Native & Ornamental Perennials & Grasses
38W443 Highway 64,  St. Charles, Illinois 60175
 Phone: (630) 584-0150   /  Fax: (630) 584-0185




A Midwestern Rock Garden

The diminutive, jewel-bright plants of a rock garden can make an appealing display in dry, difficult situations, even here in the alpine-unfriendly Midwest.  Just keep in mind that true alpine natives, although extremely cold and hardy, cannot tolerate our humid summers, soggy winters, and heavy, clay-rich soils.  Fortunately, alpine plants and rock garden plants are not always synonymous.  Rock garden plants cover a broad range of slow-growing, mat-forming, cushion-like perennials, many of which are undemanding, low-altitude species.  While true alpines have cultural requirements that are nearly impossible to duplicate in the Midwest, most other perennials suitable for the rock garden style require only sun and good drainage.

Choose carefully when sitting a rock garden; well-to sharply draining soil is a must.  Natural slopes, ridges, and retaining walls are good choices, but if you develop your own site for rock gardening be sure to raise the planting area to ensure proper drainage.  Use pea gravel mulch to create a well-drained, dry surface to decrease the chance of plant rot.  Dry, sunny places with poor, thin soil make ideal homes for many of the tiny, creeping perennials used in rock gardens.  Plants that require moist, rich soils can quickly fade in hot, dry situations while their durable, dwarfed counterparts thrive.

Rock garden plants provide a colorful tapestry of textures, structures, and forms.  Visit our year-old Midwestern Rock Garden display bed and see first hand the exciting variety of plants available to the rock gardener.  You will find silver-foliaged creepers like Cerastium ‘Silberteppich’ contrasting sharply with the dark green leaves of the low-growing Geranium sanguineum var. striatum and the red, succulent leaves of Sedum ‘Dragon’s Blood’.  The varying leaf textures of creeping Thymes such as the wooly, silver-gray of T. citriodorus ‘Silver Queen’ deserve close observation as they creep across the gravel mulch and in between stepping stones.  Even more delightful are the jewel-colored blossoms emerging as early as May.

The mat-forming creeping rock garden plants are especially attractive teamed with the punctuation points of taller species.  It’s hard too miss the high mound of Euphorbia polychroma in our rock garden.  It stands alone in early spring, a mound of neon-yellow bracts (the true flowers are tiny) capping off sturdy green foliage.  After blooming, the bracts fade to green for the summer and then to red in the fall.  Other spikes of interest include the blue-frost flowers of Veronica incana that rise above a silvery mat of foliage.  The native Penstemon digitalis and Penstemon pallidus will lighten up the early summer with loose spikes of pale flowers, while the larger Penstemon grandiflorus (an ideal choice for a dry, sharply-drained situation) blooms a showy violet through July.  The white and green variegated, sword- shaped leaves of Iris pallida ‘Variegata’ make a striking accent as they slice skyward through a thick mat of Wine Cups (Callirhoe involucrata).  These punctuation points are definitely exclamations!

Of course, dwarf varieties of many perennials find a good home in our rock garden.  Coreopsis ‘Nana’ bears bright, orange-yellow flowers and spreads by stolons to form a mat of dark green leaves.  The miniature Potentilla ‘Nana’ glows with tiny, bright yellow flowers, and creeps along slowly season by season.  Its dainty texture is ideal for a small garden.  Another dwarf suitable for the north side of the rock garden is Aquilegia flabellata ‘Alba’.  The grayish-blue, fan-shaped leaves grow into a neat mound, and the white flowers have a distinctive “top-knot”.  And don’t forget the popular dwarf Daylilies.  The compact foliage and tiny, pale yellow flowers of Hemerocallis ‘Eenie Weenie’ blend in nicely next to the light pink flowers of G sanquineum var. Striatum

Even Illinois natives find a home among the rocks and crevices.  Eragrostis spectabilis waits in green, compact mounds much of the season only to explode into a cloud of airy pink panicles in late summer, justifying its descriptive name of Purple Love Grass.  The low-growing cushion forming Wild Petunia (Ruellia humilis) sparkles with pale pink flowers from late June to August; an attractive native, it will perform beautifully in dry, hot conditions, self-seeding moderately each season.  The native San Phlox (Phlox bifida) forms tight mounds of bluish-white, almost star-shaped flowers in early spring, while the Prairie Buttercup (Ranunculus rhomboides) shines with waxy yellow flowers not long after.

Now we come to the valuable late season bloomers.  The mahogany-foliaged Sedum ‘Vera Jameson’ adds early season color but then brightens with pink blooms in August.  I’ve told you about the gorgeous display of Eragrostis in late summer, but another native grass, Bouteloua curtipendula (Side Oat’s Grama), draws attention well into October.  Its seeds hang on one side of a gracefully arching stem, a unique habit that is always a pleasure to see.  The lilac flowers of Allium ‘Glaucum’ also provide late season interest while its swirled, blue-green foliage holds its own throughout the summer.  Asters are a commonly used fall bloomer, and not so common Aster ptarmicoides, the Upland White Aster, adds color to our rock garden into September.

Attempting to mimic a natural landscape is always a challenge, and the miniature scale of a rock garden takes careful planning, but the result is well worth the effort.   Take a moment to count the number of different species that share our Midwestern Rock Garden.  You will be surprised at how many we were able to incorporate successfully.  Also note the wide spacing between plants, mimicking natural arid landscapes where plants compete for limited resources.  Emulating natural rock formations, choosing a suitable gravel mulch, and designing with small-statured, slow growing perennials ensures that your rock garden will be a diverse and unique landscape, much like a true alpine setting, but without the altitude.
