University of Vermont Extension
OH 41

Rock Gardening

By Leonard P. Perry, Extension Professor

Do you long to grow all kinds of flowers, but your garden is the size of a ping-pong table? Or if your lot is large, does it look just like all the others on the street? Whatever the size, is it full of rocks like many parts of our state? Then, welcome to rock gardening!

What do rock plants look like? They are dwarf--mostly under 1 foot in height--and form tight carpets, buns, or rosettes of foliage that are covered with flowers in season. Because rock garden plants are usually perennial, they grow into larger specimens each year. Rocks are not strictly necessary for the easier plants. However, rocks shelter delicate plants from too much sun, and keep roots cool. But their bold characteristics of permanence and wilderness, contrasted with colorful flowers, are what makes them so attractive and fitting in the rock garden.

Where can I get rock plants? Local nurseries may carry a few of the more common ones, but mail-order nurseries dealing with this specialty are dotted all over the country. The American Rock Garden Society operates a seed exchange for its members. Growing from seed is an easy, inexpensive way to get many plants. Most people get their plants from several sources, including trading with other rock gardeners.

Where is a good place for a rock garden? Choose a site that you can easily view and care for, in a place that gets rain and is also within reach of a hose. Rock gardens in full to half sun can grow the widest variety of plants, but there are many unusual rock plants that prefer shade. The garden will fit in best if it forms a connection with a background--evergreens, shrubs, fence, pond, etc. Ideally, there should be a separation from the regular perennial and annual borders with their large plants.

Do these plants need special soil? Many of the easier rock plants will thrive in a wide range of soils and you will want to start with them. Sooner or later, however, you will want to make a home for some more unusual plants. Suitable soil is nearly the whole secret of good luck with rock garden plants. A well-drained, but moisture-retentive soil will satisfy almost all plants. You need to have approximately 18 inches of developed soil to accommodate the long roots of rock plants.

How do you use rocks? Native rock harmonizes with gardens better than any exotic rocks you may be tempted to buy or collect. Sink rocks deeply into the soil so they are stable and look natural. Stratified limestone can be used to build ledges and terraces on slopes. Irregular boulders gathered into drifts resemble a dry stream bed. Choose all sizes of rock, from large "two-person" rocks, right down to fist-size. Arrange them in masses or groups. Don't make a fortress of solid rock, or dot them like salt and pepper all over.

What is the next step in construction? After soil is prepared, it can be shaped into gentle mounds and hollows. Fill--made of discarded rocks, bricks, etc.--can be used to raise the level of the garden, or extra soil can be prepared. Even a little height puts the plants "up on a stage," where they can be more easily appreciated.

There are two basic styles of construction: formal and informal. Formal terracing and rectangular raised beds usually look best combined with man-made structures such as houses and driveways. Informal styles remind us of the wild, and may successfully be used either near the home or at some distance from it. This is where your creativity comes in. For inspiration, visit rocky areas in the wild and other rock gardens and read rock gardening books.

What is the best way to plant for low maintenance? Nestle the plants between rocks, with spreading plants away from cushion types. Keep them watered when newly planted and during dry spells. A mulch of stone chips or gravel in a sunny rock garden or chopped dry leaves in a shady garden not only discourages weeds, but keeps the soil cool and moist. If your garden abuts the lawn, use a heavy permanent edging to exclude grass.

Easy rock garden plants
Androsace primuloidesIris pumila & cristate
Aquilegia flabellata 'Nana'Papaver alpinum
Arabis albidaPhlox, creeping kinds
Armeria maritimaPolemonium reptans
Aster alpinusPotentilla aurea "Nana'
Campanula carpaticaPrimula polyanthus & species
Crocus, wild speciesPulsatilla
Dianthus, perennial typesSaponaria ocymoides
Erigeron, dwarf speciesSilene alpestris, schafta
Gentiana septemfidaThymus
Geranium, perennialTunica saxifraga
HelianthemumVeronica, dwarf species
HepaticaDwarf conifers and dwarf shrubs

For more information on rock gardening, contact the American Rock Garden Society, 15 Fairmead Rd., Darien, CT 06820.

(Adapted from: Betty Ann Mech, A.R.G.S. Minnesota Chapter)

Edited in December 1997, based on material from 1991.

Issued in furtherance of Cooperative Extension Work Acts of May 8 and June 30, 1914, in cooperation with the United States Department of Agriculture. Lawrence K. Forcier, Director, University of Vermont Extension, Burlington, Vermont. University of Vermont Extension and U.S. Department of Agriculture, cooperating, offer education and employment to everyone without regard to race, color, national origin, sex, religion, age, disability, political beliefs, and marital or familial status.

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Last reviewed April 24, 1998.