Northern Gardener Rock the Garden Jan 2013

Rock the Garden

shrubs are miniature and the conifers are dwarf, making the plants easy to work with. Also, if you are the plant-collecting type, you can fit a lot of plants in a small space.

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You can tend a charming rock garden trough on a patio, deck, balcony or back step.

Many of the plants found high in the mountains have varieties

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By Eric Johnson

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Unite rocks and plants for a show-stopping garden style that adapts beautifully to the northern landscape.

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Staging the Garden GARDENERS LOVE ROCKS. When rocks are artfully placed in the garden as though emerging from the earth as nature’s sculpture, they complement the plants and naturalize the space. In alpine settings, rocks are functional—keeping plants warm in the winter and cool in the summer.

Rock gardening is a way to emulate the landscapes found above the timberline. Conditions are harsh and plants cling to outcroppings of rocks to grow, often forming little buns—as they are known—to survive; the higher the elevation, the tinier the specimen. Alpine plants, native to these conditions, are able to withstand cold temperatures, short growing seasons and little rainfall.

It sounds a little like gardens in the North.

Something for Everyone Those with both feet in the alpine or rock gardening world are a passionate sort, in love with the eccentric and captivating little 20

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jewels that have adapted themselves to survive in extreme conditions. Saxifrages, gentians and primulas are the language of hardcore rock gardeners.

To the everyday gardener, any time rocks and the plants that complement them unite as the stars of the show, a rock garden is born. You can begin with wherever you are and with whatever you have. You do not need to be a purist to create a beautiful rock garden in your yard, and the reasons to do so are many: Rock garden plants bring color and life to the garden in the spring—just when we need it most. The pops of pink, purple, yellow, red and orange, in addition to the pleasing textures, excite the eye.

You can adapt the rock garden style to specific conditions.

Sunny, shady, dry or moist, there are plants that will find themselves at home in your site.

Generally, rock garden perennials are 6 inches and under, the

Local garden designer, alpine plant enthusiast and all-around rock garden maven, Betty Ann Addison of Gardens of Rice Creek approaches the design of a rock garden much like the mounting of a stage play: Rock props. Betty Ann recommends beginning with three large rocks in a triangle, placing the largest boldly in front. When you place the largest rock in front, it causes the smaller ones to recede, creating a sense of depth. Place the rocks in the ground, mounding soil up and around.

Dwarf conifer setting. As a triad of set pieces, three dwarf conifers bring the alpine setting vividly to your garden. They add vertical inter-

est, and they also provide shade and wind protection for the smaller plants.

Mini-shrubs as support. As the supporting players, several minishrubs like daphne, rhododendron, spirea, creeping willow, and candytuft (Iberis) add texture.

Plant stars in the spotlight. Plant clumps of small-statured perennials as well as alpine plants like primrose, campanula, gentian, and trailing veronica throughout. Dot the space with reliable monthly pops of color, including creeping phlox (May), dianthus and geranium (June), Campanula carpatica (July and

August), and aster (September). Reserve the front for choice specialty plants. “When something is brought closer to the eye and pulled into focus, it gains in importance,” Betty Ann says.

Backdrop. Evergreens or fine-textured perennials and larger shrubs can be used at the back of and behind the garden to create a background, a natural backdrop that also blends the rock garden into the overall landscape.—E.J.

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common to traditional perennial gardens, and a healthy mix of the common and the exotic can make a pleasing rock garden.

Round out your collections with favorite garden perennials or

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Setting the Stage

use them to create a backdrop for the tinier specimens. Begin with what you know and love; then begin researching, exploring and collecting.

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You don’t need a gentle east-facing slope with natural rock outcroppings—the ideal scape, though not common in our area.

Mound up or dig down to simulate a mountainous setting, using rocks as structure, support and accent. Even a small slope—a rise of 12 inches over a 6-by-6-foot area—sets the stage.

Limestone rock holds moisture and its rugged rectangularity lends itself to forming a cliff, a stratification of the earth. Field stones can also work if they are partially buried—rocks emerge from the earth through the freeze/thaw cycle, they don’t fall from the skies. Experienced rock gardeners recommend including a path in your design to allow you to easily reach all areas of the garden to weed and coddle the plants. A small-stone mulch, like pea gravel, will discourage weeds, keep the soil cool and help hold soil in place on a steep slope while adding to the alpine look of the garden.

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and squeeze it, it should form a fragile ball that readily breaks apart. Builder’s sand is the ideal amendment; sandbox sand compacts too easily.

That said, don’t think you need to drastically alter your existing soil. True alpine plants demand good drainage, but most of the perennials that lend themselves to the rock garden will do well with average well-drained soil. You are best off choosing plants to match your soil. If you have clay, add organic matter and sand. If you have sand, add organic matter and black dirt to help hold water a bit. When you begin to collect the true alpines, begin creating pockets of perfect soil in select spots to host them.

Rock gardening is not easy, but it opens many gardeners to new, intriguing ways to be creative. Says Betty Ann Addison of Gardens of Rice Creek, “You don’t want a hobby that you can conquer right away. Challenges mixed with successes are forever interesting.”

The Soil Minneapolis-based Eric Johnson blogs at www.gardendrama.com. >>

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BETTY ANN ADDISON

Plants that work well in a rock garden generally need excellent drainage. When you take a ball of rock garden soil into your hand

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Rock Garden Resources Gardens of Rice Creek in Fridley, open Saturdays beginning in May, is the place to go for rock garden plants and growing advice. Gardens of Rice Creek staff also design and build rock gardens. www.gardensofricecreek.com The Minnesota chapter of the North American Rock Garden Society is a great place to find a rock garden mentor.

Membership in this friendly organization costs $10 a year for

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up to two members of a household. Monthly meetings—typically held at Hennepin Technical College in Brooklyn Park—host expert speakers. The chapter also maintains the rock gardens at the Minnesota Landscape Arboretum. In spring, a tour of members’ gardens—a great way to experience an established garden—is hosted, and August brings a plant sale. www.mn-nargs.org The North American Rock Garden Society website offers a great introduction and overview of the subject. www.nargs.org —E.J.

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Choosing Perfect Plants “Plants in the rock garden don’t need to be tiny, but they need to be finely textured, so the garden flows,” Betty Ann says. Soft, feathery perennials with leaves that flutter in the breeze and waving flowers atop thin stems, such as pincushion flower (Scabiosa), Geum, and columbine (Aquilegia), instill texture and movement and echo the alpine scape. Smaller plants with clustered and ruffled forms, such as hens and chicks (Sempervivum), bugleweed (Ajuga) and cacti, generally resemble the diminutive buns found in high elevations.

The following perennials have smaller varieties—6 inches and under—with many native to the alpine setting. Also, most have medium to tall well-known varieties that can fold into a rock garden or provide a backdrop. All are well-suited to the rock garden and easy to care for in well-drained soil. Pick your favorites and begin planting.

Allium Alyssum (Perennial and annual varieties, which readily reseed) Artemesia Aster Astilbe Bell flower (Campanula) Blue Fescue Bugleweed (Ajuga) Cacti Columbine (Aquilegia) Coreopsis Cranesbill (Geranium) Delphinium Dianthus Flax (Linum) Geum Heuchera Lady’s Mantle (Alchemilla) Phlox, particularly the creeping variety Pincushion flower (Scabiosa) Sedge grass (Carex) Succulents: Spurge (Euphorbia), Sedum and hens and chicks (Sempervivum) Thyme, particularly the creeping varieties Veronica Yarrow (Achillea)

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silene uniflora compacta

shooting star Dodecatheon meadia Alyssum

saxifraga crustata Allium

Specialty Plants

euphorbia myrsinites myrtle spurge

columbine and creeping phlox

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Gentiana andrewsii Bottle Gentian

Aubrietia Baby’s breath (Gypsophila) Campion (Silene) Cyclamen Gentian Moss Pasque flower (Pulsatilla) Primrose (Primula) Purslane (Lewisia) Pussytoes (Antennaria) Rockcress (Arabis) Rock jasmine (Androsace) Sandworts (Arenaria) Saxifrage Thrift (Armeria) Whitlow-grasses (Draba) E.J.