Have you ever seen a well-designed, well-constructed rock garden? I have been lucky enough to have visited several in the US and Canada. In each, I have been amazed at its beauty and the skillful combination of natural elements and plants. Each one has been in a different area, where the design of the garden, the climate, the rocks and the plants used has each been unique. However, they have all had similar challenges and rewards.
Rock gardens are not just gardens full of rocks. A traditional man-made rock garden can contain a ton (literally) of rocks, but they are placed artfully to mimic the microclimates, drainage and other needs of alpine wildflowers and other dwarf plants.
In nature, alpine rock garden plants occur in pockets between the stones where soil has blown in or scree (bits of ground up rock) has been created by the action, over eons, of wind and water. The plants that survive in those conditions have evolved over time to require excellent drainage. Their root systems are capable of clinging to often-steep mountainsides and of pushing down through the scree to reach water and nutrients far below. Most also need specific temperature and humidity ranges. Alpine plants would probably do very poorly in the average garden border, but they thrive in rarefied mountain conditions.
The good news is that you really do not have to live in the Alps or any other high mountain range to have a rock garden. With a little planning (and some work) you can create a rock garden of your own wherever you live, even at sea level, in desert or tropical areas, or where there is high summer humidity. In these non-alpine areas, your rock garden will be most successful when you mix local wildflowers, small garden plants and dwarf varieties of other plants that can be adapted to rock garden culture in your area. You can do it yourself or hire professional designers and installers to do the work for you. In either case, the idea is that the garden should look as if it were created by nature, as though the gardener's hand has never touched it.
Start by visiting rock gardens in your area. You can “visit” rock gardens in magazine photos or on line, but actually going to see local rock gardens is more instructive of what works where you live. If there is a botanical garden or public garden nearby, find out whether they have a rock garden (many do). Contact local colleges and universities with horticultural programs to see whether there are demonstration rock gardens on campus. Or, contact your local chapter of the North American Rock Garden Society (NARGS) for information about private gardens you might visit. On line, go to www.nargs.org and click on “Meetings” to find a chapter near you.
I recommend locating your rock garden in an area that receives full to part sun and is near a path you regularly walk along. It is also important to make sure you can see and appreciate it from a window inside your home. If you can see it every day, you will appreciate it all the more.
You can build it on an existing hillside or on a hillside that is constructed. Rock gardens can be made on flatter ground, but even slight elevations in parts of your garden will make it look more natural. If your rock garden will be small, you and your family can probably handle the earth and rock moving chores yourselves. However, if the garden or hillside you are building is to be large, it is best to hire licensed professionals with the experience and equipment necessary to ensure that any hills will be built safely and will stay in place even in high winds and heavy rains.
The rocks should look as natural as possible. That may sound like a no-brainer, but there are several things to consider. If possible, use rocks and boulders found on your own property. If there are none, or not enough, visit a local stone masonry yard to choose rocks native to your area that will blend with your own. Each rock has several surfaces; usually all of the back and bottom surfaces and much or all of the top and sides will be buried in the garden soil. Therefore, choose stones that have interesting “faces” (the front surface, the one that you will see most or all of) and bear in mind that the “grain” of each stone's face should run in the same direction – again to mimic nature. Size is also a factor. The stone outcroppings in an actual hillside will be of many different sizes and shapes, and that is what you want to duplicate.
Just as in any garden, you will want something to be in bloom during each season. Plan to use dwarf bulbs and other spring blooming plants, followed by summer and fall bloomers. Besides flowers, a few dwarf grasses, dwarf conifers and other evergreen plants can be used for winter interest. Bear in mind that even in alpine rock gardens, where most of the plants are quite tiny, there is variation in the overall size and shape of the plants as well as in the size, shape and color of the leaves and flowers.
Combining the rocks and the plants can be a wonderful creative exercise and fun for the entire family. Even if you are using professionals to design the garden, your input should be welcomed and acted upon. It is, after all, your garden.
For early spring bloom, snow (species) crocus will give your rock garden bright and charming bouquets of color. At about 4-6 inches tall, these 5+ cm bulbs are easy to grow and love. Crocus chrysanthus 'Advance' is yellow on the inside and purple on the outside, with orange stamens. C. c. 'Blue Pearl' is iridescent blue on the outside and creamy white on the inside. C. c. 'Dorothy' is golden yellow on the outside and a darker gold on the inside. C. minimus is even smaller at 3-4 inches tall. Its lovely flowers are white with pale lilac and a purple flame. C. sieberi 'Firefly' has violet petals with grayish veins and a yellow throat. C. s. 'Tricolor' lives up to its name, sporting with an orange-yellow base, soft violet-blue petals and a distinctive white heart. C. tommasinianus 'Ruby Giant' is gorgeous in velvety deep purple with a violet hue on the outer petals.
Giant crocus, Crocus vernus, can also be used in rock gardens where the much larger bulbs (9-10 cm) can be planted 3 inches deep. If soil pockets between the rocks are not large enough, consider planting them nearby. These beautiful plants on 4-6 inches tall stems naturalize easily and are a delight to behold when they bloom in early spring. 'Jeanne d'Arc' is snow white, while 'Flower Record' is a deep velvety purple, 'Silver Coral' is silvery pale lavender and 'Golden Yellow' is just that, sparkling in the sun! 'Vanguard' is a bi-colored beauty in shades of mauve and light grayish-mauve and 'King of Striped' is grayish white, lavishly striped with lilac-blue.
The dwarf iris are also excellent rock garden-sized plants. These diminutive charmers are just as beautiful and almost as fragrant as their taller cousins (bearded iris), but are more versatile, being also perfect for containers or spring borders that you will pass every day – though the flowers are large for such short plants, you will appreciate them more up close than planted in a distant border. They are hardy in zones 4-9; in the warmer zones they may bloom as early as February, or as late as April in colder areas. They can be tucked into small spaces and always delight their viewers. Early blooming Iris histroides 'Katharine Hodgkin' has unusual bluish-gray standards and falls with prominent spotted yellow crests and will grow to 6-8 inches tall. Iris danfordiae is also among the first to bloom, with bright canary yellow flowers with greenish brown spots on 4 inches tall stems. This iris bulb breaks into bulbets after blooming if left in the ground; it will take awhile for them to rebloom. Dig up the bulbs after flowering or plant new bulbs each fall. Iris reticulata and its hybrids will reliably rebloom each year. I. reticulata is graceful at 6-7 inches tall with narrow purple-blue standards with a bright yellow blotch. I. r. 'Harmony' is lovely with bluebird blue standards and royal blue falls with a white-edged yellow blotch. It will grow to 6-8 inches tall. At the same height, I. r. 'Joyce' is deep sky blue with a gold, white-edged blotch on the falls. I. r. 'J.S. Dyt' is purple with reddish-purple falls. It is one of the latest to bloom and grows to 6-8 inches tall.
The Dutch iris, Iris hollandia, are slightly larger at about 16 inches tall. They bloom in May-June, after the dwarf iris. Often sold in mixed groups, Dutch iris come in beautiful colors: blue, purple, lavender, white, yellow and bronzy-brown. They are absolutely delightful in zones 4-9.
A non-bulbous plant capable of blooming any time between December-May in zones 3-8 is the Cote d'Azur pink, Saponaria ocymoides. Native to the French Riviera region, this plant has semi-evergreen foliage and pink, star-shaped flowers. It grows on 4-5 inches high and can also be used as a groundcover on terraces, banks and in spilling over the edges of containers.
What would spring be without daffodils? There are some very special dwarf varieties that will grace any rock garden. 'Golden Bells' at 8 inches tall is also known as “Yellow Hoop Petticoat” because of the lovely and unique flower shape. 'Tête-à-Tête' French, literally, for “head to head”) is one of my all-time favorites. Each bulb produces several dainty yellow flowers that dance on their stems and really do look as if they are talking to each other. A little taller at 12 inches, but still dainty, is the fragrant heirloom poet's daffodil, Narcissus recurvus. It has pure white petals that curve gracefully back and a small green centered yellow cup rimmed with red. Charming!
Among the best partners for dwarf daffodils are the tiny blue grape hyacinths, which are hardy in zones 3-8. Muscari armeniacum grows 3-4 inches tall with spikes of dainty cobalt blue bells. 'Dark Eyes' is slightly taller at 6-8 inches and each tiny bell is edged with white for a charming and unusual show. A remarkable bicolor, M. latifolium, has bluish-purple flowers with delicate soft blue tops. For even more contrast, try the white grape hyacinth, M. a. 'Album' along with the blue ones.
Wind flowers, Anemone blanda, are daisy-like flowers in pink, blue and white that bloom profusely in April-May in zones 5-9. They have interesting fern-like foliage and grow to about 6 inches tall. The double flowered poppy anemone, A. coronaria 'Lord Lieutenant', is 8-12 inches tall and produces its iridescent deep blue flowers slightly earlier in the season than other anemones.
For slightly later bloom, try a few of the exquisite but less-well-known species tulips. They are hardy in zones 3-8 and will return faithfully each year without the need to divide them. Tulipa hageri 'Little Beauty' is an adorable open flowered charmer. At 4 inches tall, it blooms in a vibrant dark pink with a white-rimmed blue center. The 10 inches tall T. violacea 'Pallida' has pointed white petals that open to reveal a bright blue center.
Though most ornamental onions are tall border plants, the smaller blue drumstick allium, A. caeruleum grows 24 inches tall and will give your rock garden some unexpected interest. Its tight 1-inch-wide flower clusters appear in May-June in zones 3-8. After the flowers dry, they can be left on the plants all season for an unusual look.
For summer bloom, there are several outstanding small perennials you might consider. Gaillardia 'Goblin', also known as blanket flower or fiesta daisy, will bloom prolifically from June-September in zones 3-9. The gaily colored, daisy-like flowers are fiery orange-red edged in golden yellow. Blooming at the same time in the same zones but in soft pastels is bell flower, Campanula medium. Growing from 8-24 inches tall, they are lovely in blue, pink, lavender and white.
I'm a sucker for variegated foliage and here's a plant small enough at 16 inches tall and wide for some rock gardens in zones 4-9, blooms all summer and has narrow green leaves edged in gold. It is Coreopsis 'Tequila Sunrise' and even its flowers are remarkable -- large and golden yellow with red markings all around the centers.
How about a fragrant perennial with blue foliage that has been named the 2006 Perennial of the Year by the Perennial Plant Association? Dianthus 'Firewitch' grows 7-8 inches tall and is covered with luminous magenta pink, upward-facing flowers from June-September in zones 3-9. The foliage is silvery blue and the fragrance is of spicy cloves.
Hardy geraniums are reliable perennials that are as adaptable as they are beautiful. Two, in particular, are good choices for rock gardens. Geranium sanguineum, the cranesbill geranium, produces magnificent purplish-red blossoms from June-September on 10 inches tall plants in zones 3-8. The lacy, dark green leaves form compact mounds from which to flaunt the gorgeous flowers. At 12 inches tall, G. s. 'Album' produces small white five-petaled blossoms from June-August. The foliage is just as dainty, forming dense, lacy dark green mounds – the perfect backdrop for the almost non-stop flowers.
For daylily aficionados (and aren't we all?) two of the smaller daylilies (Hemerocallis) are perfect. 'Little Grapette' grows only 12 inches tall in zones 3-9. This little charmer produces dainty 2 inches wide grape-colored blossoms from June-July. 'Little Business' is slightly taller at 15 inches and has bluish-rose-red recurved blossoms at about the same time. Both have semi-evergreen foliage.
There are many small, sprawling sedums that should do well in rock gardens from Arizona to Alabama. Sedums are mostly succulent plants native to dry regions but can adapt to other situations. One in particular, Sedum 'Red Cauli' has attractive red-tinged foliage that sets off the bright red, ball-shaped flower clusters to perfection. The plant looks great all season and blooms in August-September in zones 3-10. After the flowers fade, they are replaced by attractive seed heads that add interest all winter.
For fall bloom, hardy Cyclamen cilicium has fragrant flowers of rose pink fading to light pink at the edges held above its spotted green foliage. C. hederefolium has soft pink flowers and semi-evergreen foliage. Both plants grow to 8-12 inches tall in zones 5-9.
Autumn flowering colchicum and crocus are aptly named; they grow to 4-6 inches tall in zones 3-9 and though they bloom around September-October, they really do resemble spring blooming crocus. 'Autumn Blue', 'Autumn Gold', 'Autumn Lilac', 'Autumn Rose' and 'Autumn White' are described by their names and Saffron crocus, Colchium sativus, is lilac with orange stems. Rose colchicum, C. cilicicum, has large flowers in deep lilac; C. 'The Giant' has lilac flowers up to 8 inches wide; C. 'Double Waterlily' has gorgeous fully double lilac flowers; and the white waterlily colchicum, C. alboplenum, has exquisite double flowers of creamy white.
I hope these suggestions will inspire you to build a rock garden of your own. Rock gardens, like water features, meditation gardens, herb gardens, cottage gardens and all the other garden styles are meant to be adapted to your own landscape, climate, time, energy, budget and plant choices. That makes your garden uniquely your own, to be enjoyed for years to come.
