How to Build a Crevice Garden

This take on a rock garden creates the perfect conditions to grow many underused, low-maintenance beauties

Fine Gardening – Issue 181
crevice garden
You know you want one. The uniqueness of crevice gardens means they can’t help but catch the eye. The repetition of the lines of the rocks provides a unifying element among a wide variety of plants.

If this is the first time you’ve come across the phrase “crevice garden,” it won’t be the last. This style of gardening is on the tongues of every gardening taste maker I know and is an approach to gardening whose time has come. Crevice gardens bring together a number of elements that make them must-haves in the modern garden. They are water-wise, architecturally striking, perfect for small gardens and containers, and provide ideal conditions for growing a wide range of beautiful and unusual plants. Most critical, they represent a style of gardening that not only brings a striking, fresh aesthetic to the garden but also provides ideal conditions for a wide range of plants and helps them survive whatever extremes our climates throw at them. So whether you garden in steamy North Carolina, high-and-dry Denver, or frigid Maine, crevice gardening will work for you and allow you to grow a wide range of fascinating plants.

crevice garden on corner of border
Photo: Steve Aitken

What and why

The concept of a crevice garden is deceptively simple: It is just a series of large, flat stones set together vertically like the pages of a book, with soil between each stone, making a series of narrow, deep crevices for your plants to grow in. As plant roots begin to grow out, they hit the stones and are guided downward, plunging deep into the structure of the crevice. So instead of a wide, shallow root system, you get a deep, drought-resistant one that’s insulated from extremes of heat and cold. At the same time, the structure of a crevice garden lets water drain quickly away from the soil surface, so the crowns of plants like alpines and hardy succulents stay dry and thrive in rainy climates where they would usually rot out.

crevice garden with large rocks in the shade

A crevice garden gives you those magical “moist but well-drained” conditions you always hear about but that don’t seem to actually exist in the real world. In a crevice, plants don’t drown in the wet or shrivel up in a drought. That is what makes growing in a crevice garden so different from trying to coax something to flourish between the pavers of your patio or a path. At the surface, it looks the same, but under that patio, the soil is heavily compacted to avoid settling, so plant roots stay shallow and only the toughest survive. In a crevice, roots plunge deep, so you can grow even the fussiest of plants with ease.

Aside from being a dreamily perfect venue for growing many plants, crevice gardens also bring kick-ass aesthetics to the garden. For me, the most powerful feature of a crevice is the balance of hard and soft. The stones are austere, and the crevices, though actually wonderful places for plants to grow, look harsh and limiting. And amid all that hard austerity, you have beautiful, delicate-looking plants that are absolutely thriving. A planted crevice garden to me speaks of beauty and life overcoming long odds and harsh conditions—symbolism we can all do with more of.

close up of crevice garden
Tighter is better. The narrow crevices force roots down, which insulates them from temperature extremes and provides them with access to water and nutrients in times of need.

The other great visual feature that crevices provide is unity and repetition in the garden. This need for repetition is old news: Never just plant one of anything, the designers always tell us; plant in drifts and repeat key plants, colors, and forms through the garden to pull it together. I know this. I understand why it works to create a beautiful, coherent garden. But then I go to the nursery and fall in love with 20 different plants and end up planting in dramatic drifts of 1. I can’t help it—I’m a plant nerd. With garden space always at a premium, how could I possibly let repetitions of just 1 or 2 varieties take up so much valuable real estate? It can be done, but it takes a lot more control and self-restraint than I have.

But in a crevice garden, the stones—not the plants­—serve as the main unifying repetitive feature. By using the same stone throughout, you create a steady, repeated element of form, color, and texture, which draws together and makes a cohesive whole out of even a wild collection of different and disparate plants. Build multiple crevice gardens with the same stone around your property, and you’ll get even more unity, a strong, cohesive structure, and a design that will stand up to the most unrestrained of plant collections

Building one only takes a few steps

When you set out to build a crevice garden, the first order of business is to choose your stone. In practical terms, all that is required is that the stones are large and fairly flat. Often the most available suitable stones are those sold as pavers for patios, but any large, flat-ish rock will work. If you already have stone in the garden, using the same material or one that looks similar will make the crevice appear more natural and integrated into the larger garden. This could mean trying to match the color of local stone that is visible in your neighborhood, buying the same pavers that you used for your patio and turning them on their side, or—if you live in an urban area—even using old, broken-up concrete (aka “urbanite”) to match the sidewalks around you.

crevice garden illustrated
Illustration: Conor Kovatch

1. Anchor the ends

When you’ve got your stone and are ready to start building, the first step is to install and anchor the end stones. A crevice garden is, really, a kind of raised bed, and the stones at either end are going to wind up supporting the weight of that bed. If the garden is low, the weight isn’t that much of a concern. But if you build up very high, you need to be sure to plant the stones at the end firmly and deeply so that the whole structure doesn’t wind up leaning over and collapsing. Choose a thicker piece of stone, and then bury it up to half its length in the ground, firmly packing the soil in around it so it won’t budge.

Once your end is up, you can start installing your other stones. How far apart you space them is up to you, but I’d encourage you do go closer rather than farther. The bigger the crevice, the less of the crevice effect you will get in how plants grow, and I feel that tight, small crevices give a more natural shattered-rock effect. Whatever you do, take the time to make sure each stone goes in at the same angle as the stone before it. If they’re all every which way, the final effect will just look messy.

2. Add a soil mix of sand and gravel

Once your stones are placed, add a mix of sand and gravel between them. For this, you want to lean hard on fine gravel and sand (sharp rather than rounded in both cases) to give you a loose, well-drained mix that the plants will be able to quickly grow down through. I generally opt for 2/3 sand and 1/3 gravel. Everyone has their own ratio, but that is a good starting point. In general, in hot humid places like the Southeast, you want more gravel, and in dry places like the West, more sand.

3. Top off with gravel

In the ground or in a container, finish off by topping the final inch with a fine gravel mulch that matches the stone in color. This will look great and help keep the crowns of alpine and succulent plants dry and healthy. Pour the soil mix in, use a stream of water from a hose to settle it into place, and top it up if needed. If the crevice is very high, the soil mix may wash out of the crevices in heavy rain. Once the plants are installed and rooted in, they’ll hold the soil in place, but in the meantime, place small chips of rock in the crevices along the sides to act as little dams to stop the loss of the soil.

4. Remove potting soil before planting

Now you are at the best part of any new garden: planting! When shopping, look for small plants in small containers that will fit easily into your crevices. And in most cases, I recommend removing most of the potting soil from around the roots of your plants. Generally, nursery plants will be grown in a moisture-retentive media, which will hold too much water around the crown of the plant; the roots won’t be inclined to grow out of that into the drier soil mix around them. Removing the potting soil also makes it easier to fit plants into tiny crevices.

Most plants will take being bare-rooted without missing a beat. Just be sure you get them planted immediately so that the exposed roots don’t have a chance to dry out. Pull the roots straight and tuck them down as deep as possible into the crevice, refill around them with your gravely sandy soil mix, and water them in.

Maintenance is minimal

Once planted up, a crevice garden should be quite low maintenance. In most climates, the well-drained gravel mulch will be too dry for most weed seeds to germinate and get established, and the small, slow-growing plants won’t need dividing regularly.

Most plants you’d use in the crevice garden are adapted to low water and lower fertility, so in rainy climates you won’t need to irrigate at all once plants are established, and in drier places you’ll be able to cut back the irrigation you would normally use. And fertilizer needs will also be minimal. If you want to encourage lush growth, especially in the container gardens, use a very diluted fertilizer in the spring. But most of the plants will thrive and look good with little or no supplemental fertilizer, and growing them lean will help keep them small, compact, and the right size for a smaller garden.

5 Plants to Get You Started

An enormous variety of plants can thrive in the well-drained environment of a crevice garden. Here are a few ideas you might enjoy.

Alpine geranium
Photo: Joseph Tychonievich

small hosta
Photo: Steve Aitken

Silver-edged primrose
Photo: Joseph Tychonievich

1. Alpine geranium

(Erodium reichardii and cvs.)

Zones: 7–10

Size: 3 to 6 inches tall and 12 inches wide

Conditions: Full sun to partial shade; well-drained, neutral to slightly alkaline soil

2. ‘Blue Mouse Ears’ hosta

(Hosta ‘Blue Mouse Ears’)

Zones: 3–8

Size: 6 to 12 inches tall and 9 to 12 inches wide

Conditions: Partial to full shade; medium, well-drained soil

3. Silver-edged primrose

(Primula marginata and cvs.)

Zones: 3–9

Size: 6 to 8 inches high and wide

Conditions: Partial shade; well-drained soil

Cobweb hens and chicks Hendersons daphne

4. Cobweb hens and chicks

(Sempervivum arachnoideum)

Zones: 5–8

Size: 1 to 2 inches tall and 4 to 6 inches wide

Conditions: Full sun; dry to medium, well-drained soil

5. Henderson’s daphne

(Daphne × hendersonii)

Zones: 5–8

Size: Up to 18 inches tall and wide

Conditions: Full sun to partial shade; well-drained soil

Joseph Tychonievich is the author of Rock Gardening and Plant Breeding for the Home Gardener. He studied horticulture, plant breeding, and genetics at the Ohio State University.

Photos, except where noted: Joseph Tychonievich

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