Dozens of plant species naturally grow in, on, and between rocks, from tiny alpine rosettes clinging to cliff faces to ferns sprouting from old stone walls. These plants, collectively called lithophytes, draw most of their nourishment from the atmosphere, rainwater, and the thin layer of organic debris that collects in crevices rather than from deep soil. Whether you’re curious about the biology behind this or looking for species to plant in your own rock garden, the list is surprisingly long and varied.
How Plants Survive on Bare Rock
Growing in rock requires solving two problems: anchoring roots with almost no soil and finding enough nutrients to stay alive. Rock-dwelling plants manage both through a combination of specialized root systems, slow growth rates, and partnerships with fungi. Mycorrhizal fungi, which attach to plant roots, produce organic acids and enzymes that gradually dissolve minerals from stone surfaces. This process, called mineral weathering, releases nutrients like phosphorus and potassium directly into the root zone. The fungi are fueled by sugars the plant produces through photosynthesis, creating a loop where the plant feeds the fungus and the fungus feeds the plant.
Most rock-dwelling species aren’t picky about growing exclusively on stone. Research on ferns and related plants found that strict specialists, species occurring almost entirely on rock, were a minority. Most showed a clear preference for rocky habitats but could also grow in soil when conditions allowed. This flexibility is one reason you’ll see the same species thriving in a gravel path, a stone wall, and a natural cliff face.
Alpine Rock Plants
Some of the most iconic rock-dwelling plants come from mountain environments, where they’ve adapted to extremes that would kill most garden plants. Two groups stand out: saxifrages and sempervivums (commonly called houseleeks or “hens and chicks”). Both grow in low rosettes, clusters of leaves arranged in circular patterns that hug the rock surface. This shape keeps them out of the wind while maximizing the leaf area exposed to sunlight.
At the Royal Botanic Gardens Kew, alpine plants are grown in holes drilled into tufa rock, a porous type of limestone, with no compost at all. Their roots anchor directly into the stone. These plants survive six months buried under snow, then endure intense summer heat. The key to their survival in warm months is snowmelt running continuously through their root zone, keeping them cool, hydrated, and supplied with dissolved minerals. Their slow growth rate is itself an adaptation: staying small reduces the risk of outgrowing the meager resources available in a crack or ledge.
Alpine rock plants also re-root easily after being dislodged by avalanches or landslips, which means they can colonize freshly exposed rock surfaces quickly. This resilience makes them forgiving choices for gardeners, too.
Sedums and Stonecrops
Sedums are the workhorses of rocky, dry environments. Their thick, water-storing leaves let them survive in places with almost no soil moisture, and many species spread as ground-hugging mats that fill gaps between stones naturally.
- White sedum (Sedum album): White summer flowers over green foliage that turns reddish in fall. Thrives in thin, poor soil and rocky embankments.
- ‘Angelina’ stonecrop: Gold leaves that shift to bronze in cold weather, with small yellow flowers through summer. A fast-growing, mat-forming plant that fills crevices in stone walls and rock gardens.
- Golden Japanese stonecrop (Sedum makinoi ‘Ogon’): One of the few sedums that tolerates partial shade, making it useful for rock gardens that don’t get full sun all day.
- Pink Mongolian stonecrop: Especially well suited to dry soil and rock garden pockets.
- ‘Purple Emperor’: A more upright plant with deep plum foliage and pink flowers. Works well tucked into pockets in rock gardens rather than spreading across surfaces.
Sedums are reliable for filling chinks in stone walls because they need so little to establish. A small piece of stem pressed into a damp crevice will often root on its own.
Ferns That Grow on Stone
Ferns might seem like an unlikely fit for bare rock, but several species are commonly found colonizing walls, bridge abutments, and masonry. Ebony spleenwort (Asplenium platyneuron) frequently invades old brickwork and mortar joints across eastern North America. Tennessee bladder fern (Cystopteris tennesseensis) grows on stone walls with or without mortar, at the tops and bottoms of walls, on mossy surfaces and bare ones. Observations from the Philadelphia area show it in a wide variety of microhabitats, from tidy suburban walls to surfaces bearing graffiti.
Rock-dwelling ferns need more moisture than sedums or alpine rosettes. They do best on north-facing or shaded stone where humidity stays higher and direct sun doesn’t bake the surface. One challenge for ferns on urban stone is the heat island effect: paved surfaces and walls absorb and radiate heat in summer, pushing temperatures higher than many ferns can tolerate. Species that succeed in cities tend to be those whose native range already includes warmer climates.
Mosses and Lichens
Mosses are often the first colonizers of bare rock. They lack true roots, instead using thread-like structures called rhizoids to grip the surface. They absorb water and nutrients directly through their leaves from rain and humidity. Over time, mosses trap dust and organic particles, building a thin layer of proto-soil that larger plants can eventually root into. Lichens, which are partnerships between fungi and algae, play a similar pioneering role, slowly etching into rock surfaces through chemical weathering and creating the first footholds for other life.
Rare and Endangered Rock Plants
Because cliff and rock habitats are naturally fragmented, the plants adapted to them can be vulnerable. In the Taihang and Yan mountains of North China, researchers have documented a cluster of rare species found only on limestone cliffs, including an endangered honeysuckle relative called Lonicera oblata. This deciduous shrub is listed as a nationally protected species in China, threatened by logging, mining, overgrazing, and tourism. Its survival depends on preserving not just the cliffs themselves but also the pollinating insects and surrounding plant community it relies on.
Several other rare lithophytes share the same cliff habitat in that region, each endemic to a small geographic area. The pattern repeats worldwide: isolated rock outcrops often harbor species found nowhere else, making them conservation priorities even when the total area of habitat is small.
Planting in Rock Crevices at Home
If you want to grow plants in rocks intentionally, the technique is straightforward but different from normal gardening. According to Penn State Extension’s guidelines for building crevice gardens, the gaps between stones should be 1 to 2 inches wide. The base layer is about 6 inches of coarse sand, topped with 2 inches of fine gravel (around three-eighths of an inch).
The planting process itself is the opposite of what most gardeners are used to. You want to bare-root the plants completely: lift them from their pot, shake off all the potting soil, then rinse the roots clean. Set the bare roots into the crevice, backfill carefully with fine gravel, and push more stone chips around the plant right up to the crown. The goal is drainage so fast that the roots never sit in standing water. For container-sized crevice gardens, the same principles apply, with just a handful of soil mixed into the sand to provide trace nutrients.
Good starter plants for crevice gardens include sedums, sempervivums, saxifrages, and compact thymes. All of these tolerate the lean, fast-draining conditions that rock crevices provide, and most are winter-hardy across a wide range of climates.