Pep Up Your Rock Garden!

Rock gardens are beautiful in May and June, but after that they look so dull!” Haven’t you heard that remark or thought the same thing?
Rock gardens are in their glory during these two months, but they need not lack beauty the remaining ten months of the year.

Well Planned Rock Garden

In a well planned rock garden, there is always beauty of line, a sense of strength and stability from the rocks, a contrast between rocks and plants and a play of light and shadow.

As the floral display wanes, the forms of the individual plants become evident; the patterns, color and textures of their foliage command attention. With careful selection and proper placement of plant material, interest can be kept alive in the rock garden practically the year round.

Phlox brightens rock gardens

During these early months, alyssum, arabis, armeria, aubrieta, campanula, dianthus, dwarf iris, primroses and phlox make the rock garden a galaxy of color. But after that rock gardens need some plants to enliven the scene the rest of the year.

Dianthus deltoides and D. gratianopolitanus graciously carry over into July if the faded flowers are promptly removed.

Some named varieties, will continue to flower intermittently until November, provided their blooms are picked before they go to seed. Campanulas likewise furnish refreshing flowers in midsummer. Campanula carpatica blooms from late June through September.

Sedum For Rock Garden Crevices

Sedums are an obliging group, for they are effective among rock crevices whether in or out of flower and need little care. Most of them require only ordinary garden soil and full sun.

Sedum nevi, a native eastern species, also does well in light shade. Its pinkish-gray leaves remain attractive from the time they appear in April until they vanish late in the fall.

In June, the plant is starred with dainty white flowers. Sedum middendorffianum makes a fine clump of narrow, toothed dark green leaves brightened in July by yellow flowers.

Sedum kamtschaticum follows with rich yellow flowers in August; its leaves stay a refreshing light green all season.

But the most beautiful of the sedums, in my estimation, is Sedum sieboldi. The rounded, fleshy leaves, borne singly along gracefully arching stems, are a bluish green, tinged at the edge with pink, which is especially noticeable in the fall. The flat heads of rosy pink flowers dress up rocks in September and October.

The Perennial Border

Everyone is familiar with the 3-foot coreopsis of the perennial border, but few are aware of the low-growing coreopsis, Coreopsis auriculata.

Above tidy clumps of basal leaves, some of them evergreen, the golden yellow “daisies” are lifted all summer long on wiry, 8-inch stems. Coreopsis auriculata likes well-drained, loamy soil and performs better in light shade than in full sun.

Gypsophila repens and Gypsophila repens bodgersi carry their airy sprays of white flowers above mats of bluish-green leaves throughout most of the summer. Gypsophila fratensis, of somewhat more trailing habit, produces sprays of clear pink flowers in June and July and again in September.

Gypsophila fratensis is a pretty companion for the delightful Aster alpinus. This produces lavender-blue flowers on 8-inch stems above a clump of hairy green leaves throughout June and July.

Another July-blooming aster is Aster meritus from the Dakota prairies. It wants full sun and well-drained soil and when grown under such conditions covers itself with violet flowers.

From the same part of the country and liking similar conditions is Aster kumlieni, which forms a low, broad mat of color in September. The ray florets are a lovely blue, the disc florets a golden yellow.

A. durnosus starts flowering in September and continues into October, its compact mounds of dark green leaves almost hidden by the wealth of blooms. There are several color forms of this native eastern species.

In light to fairly heavy shade, the little plumed bleeding-heart (Dicentra eximia) and Dicentra formosa never seem to tire of putting out their heart-shaped flowers. They are going strong from June until October.

In November last year I counted a dozen or so flowers. The blooms of Dicentra eximia are rose pink, those of D. formosa, rose-purple.

The exquisite white-flowered form with delicate fernlike foliage of the dicentras is pleasing all summer and into early fall. They like a leafmoldy loam and will endure some sun if the soil never dries out.

Companion plants to the dicentras are their cousins, corydalis, which enjoy the same growing conditions and have the same long season of bloom. Their showy yellow flowers and light lacy foliage add a graceful touch to the rock garden.

Bulbs Extend The Season

Bulbs contribute substantially in extending the season of interest. The lovely Iris reticulate and the winter aconites lead off, followed by the early spring crocus, snowdrops and snowflakes, miniature narcissus and species tulips. Erythroniums, fritillarias and hardy cyclamen continue the procession, which ends with colchicum, the autumn crocus.

Even in winter, the rock garden will reveal fascinating contrasts. Then the little tufted mats of dianthus stand out in a soft gray-green mass, while Phlox subulata shows a patch of dull green between rocks.

The leaves of Shortia galacifolia glisten in bronzy tones, as do the leaves of wintergreen (Gaultheria procumbens) and Galax aphylla. Mitchella repens, or partridge berry, remains a deep green, its leaves hung with bright red berries.

4 Excellent Evergreen Groundcovers

These last four are excellent evergreen groundcovers. Sempervivums cling to rock crevices in different shades of gray-green and ruddy red. The Christmas rose, tucked away in a shady corner, bears its exquisite blooms from late November or early December, depending upon the locality and vagaries of the weather, until after the turn of the year.

It is at this season that shrubs are fully appreciated. Throughout the year, they serve as accent plants and emphasize the vigor of the rocks.

Come fall and winter, they give distinctive character to the rock garden. Dwarf conifers are particularly adaptable.

In form, they may he prostrate, rock-hugging, slender, conical spires or cushionlike mounds. The color and texture of the foliage is as diversified as the habits of growth. Those of blue-green, gray-green and dark green tones are preferable to conifers with yellow-green and variegated coloring.

Mugho pine has a dark green color and strong texture, while Chamaecyparis obtusa nana gracilis is emerald green, with a fine texture.

Juniperus communis compressa, a real dwarf rarely exceeding 2 feet in height, has a spirelike form which fits at the base of a ledge. J. horizontalis prostrate spreads a flat mass of blue-green over rocks. Dark green Taxus baccata repandens has a stiff appearance, and many of the dwarf spruces have a strong, sharp outline.

Background Plants

Broad-leaved evergreens, rhododendrons, mountain laurel, andromeda, leucothoe and some of the hollies are excellent background material. The leaves of Rhododendron carolinianum have a warm bronze tint in winter, and the stems and buds are a pleasing cinnamon brown. The buds open in May into beautiful rose pink flowers.

Daphne eneorum, though at times a problem child, is one of the loveliest low-growing shrubs for the rock garden. Its small leaves, which cover the trailing branches from top to bottom, are a soft green; its rosy pink flowers, which bloom in the spring and frequently again in September and October in less quantity, are deliciously fragrant.


A gritty limestone mixture incorporated deeply with sand, garden loam and leafmold seems to suit it best. Perfect drainage and a good share of sunlight, though not full sun, are also necessary to make it happy. It makes a pretty picture against limestone rocks.

Heaths and heathers, or cantinas and ericas, are not easily satisfied, but rock gardeners who give them the conditions they demand find these dwarf evergreens richly rewarding. They want full sun and sandy, acid soil in which peat and humus have been incorporated.

Some varieties bloom as early as March and April and others from June until September or October, so that a planting of them prolongs the period of bloom in the rock garden and furnishes interesting foliage effects. The numerous named varieties of Cantina vulgaris are popular.

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