The Best Plants for Rock Gardens

Geranium Cranesbill

Geranium Cranesbill (Photo: greengatefarms.com)

Rock Gardens first became popular back in the Victorian era when avid plant collectors of the time searched high and low for something new and different. Indeed they found them in the very high Alpine mountains where the plants themselves grew rather low to the ground. Planting these new discoveries in their cottage gardens back home wouldn’t show off these alpine plants to their advantage, however. These delicate, small plants would be easily swallowed up by more showy perennials and annuals common to the cottage garden or the more formal perennial border. Thus came the need for a way to display them for the best impact. That is how the rock garden came to be.

The best rock gardens are on sandy, dry, rocky hillsides or slightly sloping areas to mimic the natural environment for these plants. This allows the plants to be viewed at eye level and also provides excellent drainage, something Alpine plants require above all else. As for the plants best suited to a rock garden in your own yard, look for miniature, dwarf, low and/or slow growing varieties.

The rock garden is an excellent place to start practicing bonsai horticulture. This is taking slow growing plants and slowing them down further through careful pruning. Of course, using dwarf varieties accomplish the same thing as long as you continually prune to maintain the small size. Just because plants are labeled dwarf doesn’t mean they stay small. Let’s take a look at an assortment of readily available plants for the typical rock garden.

Friendly advice…

Before starting a rock garden, visit a botanical garden in the same USDA zone your garden resides. They may have a rock garden from which to get ideas and perhaps to emulate. You will see the specific plants used, how they work together and how to plant them for the best visual impact. Then you can decide which most appeal to you and which would work in your particular yard.

Trees

Dwarf Balsam Fir (Abies Balsamea “Nana”) is a wonderful little tree for the rock garden. Unlike its taller, more impressive cousins, this one looks a bit squat but has the typical Balsam scent and stiff branching.

Dwarf Japanese Red Maple (Acer Palmatum Atropurpureum) There are too many cultivars perfect for the rock garden to mention all of them but the smallest, most adaptable and most easily available would be the Burgundy Lace and the Crimson Queen. Both can easily be pruned to form small weeping mounds.

Hinoki False Cypress (Chamaecyparis Obtusa)- This is a golden evergreen growing upright with branch tips that weep slightly. Make certain you get “Nana Gracilis” not just “Gracilis”. Both are considered dwarf but the second one can get to 20 feet high while the other, a miniature, only grows to 4 feet, a much better choice for the small scale garden.

Shrubs

Red Leaf Japanese Barberry (Berberis thunbergii “Atropurpureum Nana”) are considered a bit of an invasive species in some areas of the United States where they have escaped into the wild, but this particular miniature “Crimson Pygmy” growing 1 1/ 2- 2 1/ 2 feet high is quite safe in the home garden. It makes a nice backdrop to smaller plants with its gracefully arching, brightly red colored leaves on spiny branches and tiny yellow flowers in spring followed by little berries which attract birds.

Scotch Heather (Calluna vulgaris) is an evergreen shrub with a craving for acidic soil. It has tiny leaves and sprays of small, bell shaped flowers in rosy pink, pale to deep pink, white, lavender and purple. Different cultivars have foliage in russet, gray, pale to dark green and Chartreuse which often change in winter. This choice is truly a wonderful plant for the rock garden. Varieties range from 2 inches high to 3 feet. There are too many cultivars to name but the best for rockery is “Nana Compacta” growing 4 inches high with purple flowers.

Heath (Erica)- Another acid loving, evergreen shrub with small needle-like leaves, Heath is often mistaken for Heather. They are so low growing they act more like a ground cover than a shrub.

Perennials

Pinks (Dianthus) make a great addition to the Rock garden as they spread low to the ground. Cheddar pinks (Dianthus Gratianopolitanus) is a pretty greyish-green leaved cultivar with spicy clove scented single flowers in palest pink. It grows 9-12 inches high with the flowers sticking above the foliage.

Stonecrop (Sedum) thrive in the rock garden. “Goldmoss” has bright yellow, star shaped flowers in spring and light green teardrop shaped leaves. This is widely available but can become invasive as it roots readily along its long, slender stems. Sedum “Dragon’s Blood” is more easily kept in check and has brilliant red flowers in early spring. Hens and Chicks (Echeveria Elegans “Imbricata” and “Secunda”) though not Sedums are succulents common to rock gardens. They grow in ever-expanding clusters of grey-green rosettes sometimes tinged with purple or red.

Cranesbill (Geranium)- These are not Pelargonium, the showy, tropical flowers commonly, though mistakenly, called Geraniums. The true Geranium is a hardy perennial perfect for woodland and rocky alpine gardens. These make pretty, tightly packed mounds of finely divided deep green leaves with small yet abundant flowers in pink, white, blue and purple. “Johnson’s Blue” is a readily available cultivar with blue-violet 2 inch blossoms.

Small scale spring blooming bulbs can be scattered amongst the other plants for added early spring color. Scilla (Siberian Squill) stands 3-6 inches tall. Daffodil (Narcissus “Tete-a-tete”) is a small scale daffodil growing 6-12 inches high. Crocus come in many varietoes and sizes but all small enough for the rock garden. Grape Hyacinth (Muscari) is a vivid blue-purple and stands 6-8 inches tall. Allium Ostrowskianum “Zwanenburg” are cute, star shaped flowers which form clusters about an inch wide and stand just 6 inches high. Miniature Dwarf Bearded Iris can also be added.

Any combination of these plants will look great in a rock garden. All that is needed is a gardener with a bit of the mountain climber spirit to gather some of these plants and design the perfect little alpine retreat suitable to their own landscape. Learning to yodel is purely optional.

Glory Lennon
 

Glory writes about flower gardening and other gardening subjects in addition to her serial romance novels from the Pocono Mountains of Pennsylvania, USDA Gardening Zone 5b

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