Crevice Plantings: Gardens in Miniature

By: Kate Frey

Kate Frey, a horticulturist and designer specializing in habitat gardens, formerly managed the garden at Fetzer Winery in Hopland, California….

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Well-established crevice plantings help to blend the steps into a hillside garden. Author’s photographs

A garden’s cracks and crevices—between  stair treads, at the base of retaining walls, and around boulders—are, for most of us, places where we sigh and get an old screwdriver to pry out tenacious weeds. We usually think of them in terms of not tripping or of controlling unwanted invaders, but seldom of artistry.

Gary Ratway, landscape designer and master plantsman, takes a different approach. He elevates these ignored and humble  spaces to scenes of delicate and surprising beauty. In his hands, crevices are destinations, places to pause along a staircase or in front of a retaining wall—to linger and admire the surprising plant combinations of these gardens-in-miniature. The flat surfaces of the hardscape become a visual frame for tiny blossoms, delicate foliage, billowy mounds, and, sometimes, spectacular flower spikes. Plants creep out of his crevices and give the gardens an established look, as if their denizens have integrated completely into the site—nature at work with the hand of man. These crevice gardens blur the line between plantings and hardscape, creating a feeling of connection between two disparate elements and generating a sense of vitality and life.

A trim crevice planting of blue sedge (Carex flacca, syn. C. glauca) with occasional seaside daisies (Erigeron glaucus)

Crevices offer shelter in places like the cold and windy Northern California coast, where salt-laden winds almost incessantly buffet exposed plantings and burn sensitive foliage. Stairs, retaining walls, and boulders deflect the wind while they reflect and radiate the sun’s energy, warming plants even after the sun goes down. In warmer, sunnier locations, the same structures and objects provide shelter from the intense afternoon sun. The crevices between treads and risers, or at the base of retaining walls, can be filled with a well-draining soil mix to accommodate a range of plantings. In small gardens, such crevices allow every inch of space to contribute to the whole; in any garden, they allow small plants with delicate flowers or foliage to be displayed without being overwhelmed by larger, more vigorous neighbors. A crevice can also be the perfect place to display a small collection of jewel-like succulents.

A mixture of small plants in a stairway crevice garden, including lavender cotton (Santolina chamaecyparissus), various cat mints (Nepeta), thymes, and grasses

Stairway Plantings

Stairways are about an origin and a destination, but Gary constructs them so that the journey in between is just as important. In Gary’s designs, the stairways and walls are often of rammed-earth construction, formed in situ from native    soil.  Some can be seen in the gardens around their home at Digging Dog Nursery, which he and partner Deborah Whigham have built over the past twenty years in Albion, California. The plantable space in each stairway varies depending upon the desired effect, but occupies a small enough area  that  the  treads  still  have  sufficient  room for feet of all sizes; admittedly, a little care needs to be taken to avoid stepping on some of the plants.

Gary makes sure that each stairway is solidly constructed on a deep bed of gravel, so it doesn’t fail, settle, or shift. He  favors a six-inch riser with an eighteen-inch tread, which allows a gracious and easy travel and slows people down. He digs out each planting pocket after construction, removing the compacted  soil and gravel and refilling with a mix of soil and compost that is then compacted to eighty percent for stability.

Receiving protection from coastal winds, various thymes (Thymus) soften the crisp lines of a garden staircase

Usually, each tread has a uniform gap of two to six inches at the base of the riser; in some, this dimension varies with the configuration of the stairs; and, in others, plant pockets are scattered here and there. The crevice configuration and plant selection create effects varying from formal to naturalistic. With a standard-sized crevice on every tread, plants are often varied to create a more naturalistic effect, as if the plants seeded themselves in place. Gary favors planting from narrow, deep plant band pots, such as the 2.5- by 5-inch bands used at their nursery. The narrow profile works well in the constricted space of the crevices, and the extra depth helps plants establish quickly. To irrigate these crevice plantings, he incorporates a Techline drip line, usually with a nine-inch spacing of emitters, each releasing water at a rate of .6 or .9 gallons per minute.

A more substantial crevice at the base of a tall wall allows room for vertical clumps of red Lobelia tupa alternating with billowy mounds of Pennisetum orientale

Retaining Walls and Boulders

Gary uses crevices along the base of retaining walls and around boulders to create a dramatic  stage  for  displaying  plants  and softening expanses of hardscape. With fewer constraints on space, compared to a staircase, he often uses larger plants, including those with tall, brightly colored flower spikes; Lobelia tupa, verbascums, Lepechinia hastata, Kniphofia ‘Bee’s Sunset’ and other  cultivars,  catmints  like  Nepeta  racemosa ‘Walker’s Low’, and various grasses such as Pennisetum orientale produce spectacular results in these settings. He incorporates plants with rounded shapes, like lavender cotton (Santolina chamaecyparissus), Australian fuchsias (Correa alba), and lavenders (especially Lavandula xintermedia ‘Grosso’), to create soft, organic curves that contrast with the rigid lines of the walls and terraces.  In one garden, seaside daisies (Erigeron glaucus ‘Sea Breeze’ or ‘Ron’s Pink’) are used almost exclusively, their rose-colored flowers highlighted against the sandy colored walls behind them.

Planting around boulders also offers richly evocative possibilities. Plants with delicate leaves that billow in the breeze  mimic the contours of the boulders and lean into their curves; among Gary’s favorites for such situations are pink skullcap (Scuttelaria suffrutescens ‘Texas Rose’), creeping thymes   (Thymus  ‘Pink  Chintz’,  T.  pulegioides ‘Archer’s Gold’, and T. serpyllum ‘Victor Reiter’, seaside daisies, Corydalis, bleeding hearts (Dicentra),  small  heaths  (Erica),   lavender cotton, and low, mounding grasses such as Deschampsia caespitosa. Taller grasses and grass-like plants add vertical accents to break up any potential for monotony.

Low mounds of crevice plants nestle against a large boulder: pink skullcap (Scuttelaria suffrutescens ‘Texas Rose’), seaside daisies (Erigeron glaucus), and grasses

Creepers, Spreaders, and Dotters

Crevices are useful for containing the overly exuberant and the simply supine. Plants with a vigorous spreading habit can be unruly when given wide open spaces with weaker neighbors to trample; but, plants such as blue sedge (Carex flacca, syn. C. glauca), Geranium macror- rhizum ‘Biokovo’, creeping golden marjoram (Oregano vulgare ‘Aureum’) and other ornamental oreganos like ‘Kent Beauty’, some yarrows (Achillea), Mexican lobelia (Lobelia laxiflora),  and  creeping thymes are excellent in the confined conditions of a crevice. Their delicate, patterned leaves and lively flowers are perfectly displayed against the adjoining hard surfaces. In a garden on the Mendocino coast, Gary used blue sedge to colonize both tread crevices and the edges of the staircase, resulting in a delicate, but tough fringe of blue against the paved surfaces. Large, vigorous grasses, such as Miscanthus sinensis ‘Adagio’ and Calamagrostis 5acutiflora ‘Karl Foerster’, or thick clumps of mounding plants, like lavender cotton or Monterey manzanita (Arctostaphylos hookeri), can also be successfully contained in larger crevices bounded by concrete or masonry.

A single species seldom dominates Gary’s crevice plantings; a crevice composition is more likely to consist of a number of intermingled species (“dotters”). In some cases, they blend into the larger gardens on either side of the crevices; in others, they form a contained vignette. Small euphorbias (Euphorbia ‘Blue Haze’), Nepeta reichenbachiana, a bronzy cow parsley (Anthriscus sylvestris ‘Ravenswing’), geraniums such as ‘Biokovo’ and Geranium magnificum, ferns, Sideritis syr- iaca, clumping oreganos, thrift (Armeria), Calamintha nepeta, smaller lavenders, grasses, Corydalis, bleeding hearts, and skullcaps mingle with compact versions of verbascums, kniphofias, creeping thymes, and lavender cotton to create entire landscapes encapsulated in the small space of a crevice.

The richness of these crevice plantings is a joy to behold. They cause movement to slow and delight to take its place. Many plants can inhabit these con- strained spaces, and anyone can have them—to the benefit of gardens both large and small.