Plants grow among rocks by rooting in soil-filled pockets, gaps or crevices—not in bare stone. For those small, sharply drained spaces, compact, low-growing plants are usually the best fit. These six options come from Colorado State University Extension’s rock-garden list; check each plant’s hardiness and growing needs against your local conditions before choosing.
Six plants for pockets and crevices between rocks
The plants below favor sun and well-drained soil, but their size, foliage and flowering seasons differ. Bloom times are those listed by Colorado State University Extension and may shift with local conditions.
| Plant | Height | Light and soil | Flowers and foliage |
|---|---|---|---|
| Mountain alyssum (Alyssum montanum) | 4–10 inches | Sun; dry, rocky soil | Yellow flowers in April–May; gray foliage |
| Sea pink (Armeria maritima) | 4–10 inches | Sun; dry, well-drained soil | Pink, white or purple flowers in May–June; grass-like foliage |
| Basket-of-gold (Aurinia saxatilis) | 8–12 inches | Sun; dry, rocky soil | Yellow flowers in April–May; gray-green foliage. Shear after flowering. |
| Purple ice plant (Delosperma cooperi) | 2–3 inches | Sun; well-drained soil | Purple flowers from June to frost; succulent foliage. Verify hardiness and local performance; the Colorado State Extension listing notes an elevation limit in Colorado. |
| Stonecrop (Sedum spp.) | 1–15 inches, depending on species or cultivar | Generally sun and well-drained soil; select for the site | Flower color and bloom time vary by species or cultivar |
| Hen-and-chicks (Sempervivum spp.) | 1–6 inches before the flower stalk | Sun; dry, gravelly soil | Pink to red flowers, typically July–September; evergreen succulent rosettes |
Use the table to narrow choices by light and drainage first, then arrange plants by mature height, foliage and flowering season. Mountain alyssum and basket-of-gold provide spring color; sea pink follows in late spring and early summer, while purple ice plant can flower into fall frost. Stonecrops vary too much to assign one bloom period to the whole genus.
How to make planting pockets between stones
A rock garden or crevice garden is a constructed planting space, not a bare-rock planting method. In a rock garden, plants grow in soil pockets among stones. A crevice garden uses slabs set vertically with gritty growing medium filling the gaps, where roots can take hold. Penn State Extension’s crevice-garden overview and the RHS guide to creating a rock garden with alpines describe these approaches.
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- Compact, Cascading Habit: Aubrieta plants form low mats 6 inches tall with a trailing edge. Space 6–12 inches apart. A fit for rock garden plants, perfect among low growing perennials.
- Late-Spring Color: Aubrieta rockcress blooms second season from perennial flower seed, coating stones with purple. Prune after flowering to half size—fit for flower seeds perennial outdoor plantings.
- Wide Range Hardy: Suited to USDA 3–10 across most U.S. regions; deer resistant. Use rock garden seeds and flowering ground cover seeds for walls and paths; handy seed packets for gifting or storage.
For a basic rock-garden medium, the RHS suggests one part loam, one part horticultural grit and one part leafmould or coir, adjusted to suit the plants. Use horticultural grit or suitable gardening sharp sand rather than assuming builders’ sand is interchangeable; the RHS explains the distinction in its guide to growing alpines.
Planting and care
Plan for mature size
Set plants in their pots in the intended positions before planting. Leave room for their eventual height and spread so compact alpines are not crowded out. Plant firmly, then top-dress with gravel or grit, as the RHS recommends in its rock-garden plant guidance.
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- MOISTURE-RETAINING & SOFT TEXTURE: Irish Moss ground cover grows well in moist, well-drained soils and forms a soft, carpet-like surface. It pairs well with stepping stones, pavers, patio borders, rock gardens, and other low-growing ground cover plants while helping retain soil moisture in shaded areas and cooler gardens.
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Water for establishment, not by a fixed schedule
Newly planted alpines may need more regular water during hot, dry weather. Once established in a rockery, many root more deeply and need less supplemental watering. Water the soil rather than keeping foliage wet: conditions that stay too damp can cause alpines to rot. Adjust watering to the weather, drainage and individual plant rather than following one schedule for every rock garden.
Control weeds and protect low foliage
Weeds can quickly overwhelm small, slow-growing plants, making weed control a central maintenance task. Keep the gravel or grit mulch topped up: it helps keep lower leaves clear of damp soil, reduces soil splash and can hinder weed germination.
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- GRAVITY-DEFYING ROCKCRESS: This energetic, spreading plant shines in challenging spots. It thrives where others fail—in nooks, crannies between stones, and behind retaining walls. It cascades beautifully down vertical surfaces, creating a "living canvas" effect.
- ALL-LEVEL COLOR FILLER: Featuring enhanced blooming potential, it quickly covers large areas with a charming, soft glow. Even after the flowering season, the plant boasts attractive waves of gray-green foliage that stay decorative throughout the year.
- ROCK GARDEN REVIVAL: The vivid contrast of blue-violet flowers against rough stone textures elevates your garden's overall aesthetic. These seeds offer stunning variations for cascading rockeries, alpine gardens, and borders with a long-term blooming perspective.
Match plants to the site
The Colorado State Extension list is a useful reference for plant attributes, not a guarantee of performance everywhere. Check plant labels and local advice for hardiness, exposure and moisture needs. Many rock-garden plants prefer sun, but shade-tolerant options exist; choose for the conditions your site actually offers. For a natural look, Colorado State Extension recommends using low-growing, clumping plants, repeating species and avoiding overplanting.
Quick Recap
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- COVERAGE: 20,000 seeds of creeping thyme (Thymus Serpyllum) provide extensive ground coverage for gardens, pathways, and landscaping areas
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- VERSATILE PLANTING: Ideal for rock gardens, between stepping stones, lawn alternative, or as an attractive border plant that helps suppress weeds
- GROWING SPECIFICATIONS: Thrives in full sun to partial shade, reaches 2-4 inches in height, and spreads up to 18 inches per plant
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- High Germination Ease: Sow aubrieta cascade purple aubrieta deltoidea seeds in 60–65°F soil. Aubrieta rockcress sprouts in 10–14 days, ideal as flower seeds for airy borders, walls, rock gardens.
- Impressive Heat Tolerance: These purple flowers plants flourish as full sun heat tolerant plants, thanks they are drought resistant flower seeds. Great ground cover seeds for any outdoor spaces.
- Excellent for Slopes: aubrieta seeds-perennial bloom as flowering ground cover. A top pick among best landscaping plants for full sun, creating creeping flowers that resist erosion & reach 6" height.
- Year-Round Charm: aubrieta plants act as drought resistant plants and fast growing ground cover. Sow rock cress seeds perennial from flower seeds packets for a lush display in USDA zones 3-10.
- Dynamic Landscape: aubrieta seeds doubles as perennials deer resistant & perfect for erosion control plants. Rockcress seeds for planting is low maintenance ground cover & can thrive in almost no soil
Sources and regional guidance
- Colorado State University Extension: Rock Garden Plants
- Royal Horticultural Society: Create a Rock Garden with Alpines
- Royal Horticultural Society: How to grow alpines
- Royal Horticultural Society: Rock gardens: plants
- Penn State Extension: Crevice Gardens: Life Between the Cracks
- Washington State University Extension: Crevice Garden
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