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© Jason Headley, some rights reserved (CC-BY-NC) · iNaturalist
Silene acaulis
Moss Campion
Circumpolar — arctic and alpine regions of North America, Europe, and Asia
Overview
Silene acaulis is moss campion — one of the iconic cushion plants of the arctic and alpine world, forming an ultra-tight evergreen dome 1–3 inches (2.5–8 cm) tall and 8–12 inches (20–30 cm) wide. The species name 'acaulis' means 'without a stem', describing the stemless, cushion-forming habit. Bright green tiny needle-like leaves form a moss-like cushion so tight and dense that it feels almost solid to the touch — a living green dome. Pink to rose-pink five-petaled flowers 0.5 inch (1.3 cm) across cover the cushion in May and June. The species has a circumpolar distribution — found in arctic and alpine habitats across North America, Europe, and Asia — and is one of the first plants to colonize recently deglaciated terrain. The cushion form is an adaptation to extreme cold and wind — the tight, aerodynamic dome traps heat and reduces desiccation. Individual cushions grow extremely slowly (1–2 mm per year) and can live for decades to centuries — a fist-sized cushion may be 50+ years old. In cultivation, sharp drainage and cool conditions are essential — the plant struggles in hot, humid climates. Hardy to zone 2 (−50°F / −46°C). Deer avoid the tiny foliage.
Native Range
Silene acaulis has a circumpolar distribution across arctic and alpine regions of North America, Europe, and Asia. It grows on rocky outcrops, scree, and gravel at high altitudes and high latitudes.Suggested Uses
Used in alpine troughs, crevice gardens, scree beds, and between rocks at close-viewing height. A collector's alpine plant. The extreme longevity (decades to centuries) makes this a living heirloom. The tight green dome is a miniature landscape feature.How to Identify
Appearance
Size & Dimensions
Height1" - 3"
Width/Spread8" - 1'
Reaches mature size in approximately 3 years
Colors
Bloom Information
Flowering in May and June, approximately 3 weeks. Pink flowers covering the green cushion. The evergreen cushion is the year-round display.Detailed Descriptions
Flower Description
Pink to rose-pink, five-petaled, small, covering the cushionFoliage Description
Bright green, tiny, needle-like, moss-like, forming a tight evergreen cushionGrowing Conditions
Sun Requirements
Requires 6-10 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Care & Maintenance
Care Guide
Plant in full sun. Sharply drained, gritty soil — alpine scree or gravel. Keep cool — not suited to hot, humid climates. Water moderately — consistent but not wet. The very slow growth means patience is essential. Hardy to zone 2.Pruning
No pruning needed. The extremely slow-growing cushion maintains itself. Do not disturb the cushion structure.Maintenance Level
very lowContainer Growing
✓ Suitable for container growing
Minimum container size: 1 gallons