Repotting guide

When & how to repot Moss Campion (Silene acaulis)

Also called Moss Campion, Cushion Pink, Moss Pink.

More about moss campion

About Moss Campion

Silene acaulis · also called Moss Campion, Cushion Pink · flowering

Moss Campion is an iconic arctic-alpine cushion plant forming dense, bright-green hummocks studded with tiny pink to magenta flowers in early summer. Native to high mountains and arctic tundra across the Northern Hemisphere, it is one of the slowest-growing alpine plants. Perfect for alpine troughs; demands sharp drainage, cool roots, and full sun.

Mature size: 1–5 cm tall, 5–30 cm wide (decades old plants may reach 50 cm across)

Watch for — Aphids on flower stems: Spring flower stalks can attract aphids. Remove manually or spot-treat with insecticidal soap. Avoid systemic pesticides that may damage the slow-growing cushion tissue.

How to tell moss campion needs repotting

Repotting on a calendar is less reliable than reading the plant. For moss campion, watch for these signs:

Roots growing out of the drainage holes, or the rootball lifting the plant proud of the rim.
Soil that has shrunk away from the pot sides and no longer holds water.
The pot is unstable because the plant has grown top-heavy.
Old, compacted, broken-down mix that stays wet too long — for a succulent that is a rot risk, so refresh it even if the pot size is fine.

For the underlying biology of a pot-bound root system and why it stalls a plant, see our guide to spotting and fixing a root-bound plant.

How often to repot moss campion

Every 2–3 years, into bone-dry mix. Moss Campion's growth habit — extremely compact, cushion-forming perennial; one of the most dense cushion alpines; very slow growing — sets the pace. Moss Campion is an iconic arctic-alpine cushion plant forming dense, bright-green hummocks studded with tiny pink to magenta flowers in early summer. Native to high mountains and arctic tundra across the Northern Hemisphere, it is one of the slowest-growing alpine plants. Perfect for alpine troughs; demands sharp drainage, cool roots, and full sun.

What size pot to step moss campion up to

Use a pot only one size up — or even the same pot with fresh gritty mix if the roots have room. Moss Campion stores water and rots in a large pot of slow-drying soil. A tight terracotta pot that dries fast is far safer than a generous plastic one. Never up-pot a succulent by several sizes.

Not sure of the exact diameter? Our pot size calculator takes the current pot and root spread and tells you the right next size — it deliberately recommends a single step up, never a big jump.

The best time of year to repot moss campion

Spring or summer, while moss campion is in active growth and warm, is best — roots recover fastest then, and the plant is not sitting in cool damp soil. Avoid repotting a succulent in winter dormancy.

Step-by-step: repotting moss campion

Repot dry. Do not water moss campion for several days first. Working with dry roots and dry mix dramatically lowers the rot risk for a succulent.
Pick a snug, fast-draining pot. Choose terracotta one size up at most, with a drainage hole. Have gritty sharply drained, gritty, mineral, neutral to slightly alkaline ready.
Tip it out and clean the roots. Slide the plant out, crumble off the old soil, and trim any black, mushy or dead roots with clean snips.
Pot into dry mix. Set moss campion at its original depth in dry gritty mix, firming gently. Do not bury the stem deeper than it was.
Wait a week before watering. Leave it completely dry and out of harsh sun for about 7 days so any damaged roots callus. Only then water lightly.

Aftercare

Keep moss campion completely dry and out of fierce sun for about a week so any nicked roots callus before they meet moisture; watering a freshly repotted succulent is the classic way to rot it. Then resume the normal lean, dry rhythm. Do not fertilise for about 3 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for moss campion

Moss Campion wants sharply drained, gritty, mineral, neutral to slightly alkaline. Best in a mix of limestone chippings and lean loam. pH 6.5–8.0. In nature grows in rock crevices with deep, cool root runs. In cultivation, use a trough or raised bed with at least 15 cm of grit below the cushion. Never use peat-based or water-retentive compost. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting moss campion — frequently asked questions

How often should you repot moss campion?

Every 2–3 years, into bone-dry mix for moss campion. Repot moss campion every 2–3 years into a snug pot of sharply drained, gritty, mineral, neutral to slightly alkaline, ideally in spring or summer. Let it sit in dry soil and do not water for about a week afterwards so any nicked roots can callus. Over-potting and watering straight away is what rots succulents.

What size pot does moss campion need?

When is the best time of year to repot moss campion?

Should you water moss campion after repotting?

No — not straight away. Repot moss campion into dry mix and wait about a week before the first watering so any damaged roots callus over. Watering a freshly repotted succulent is the single most common way to rot one.

Should you fertilise moss campion after repotting?

Not immediately. Wait about 3 weeks after repotting moss campion. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.