Repotting guide

When & how to repot Cushion Sandwort (Arenaria tetraquetra)

Also called Cushion Sandwort, Four-sided Sandwort.

More about cushion sandwort

About Cushion Sandwort

Arenaria tetraquetra · also called Cushion Sandwort, Four-sided Sandwort · flowering

Cushion Sandwort is a tight cushion-forming alpine perennial native to the mountains of Spain and southern France. It produces tiny white flowers in late spring above dense, compact mounds of overlapping leaves. A classic choice for alpine troughs, scree gardens, and rock crevices; demands perfect drainage and full sun to thrive.

Mature size: 2–5 cm tall, 10–20 cm wide

How to tell cushion sandwort needs repotting

Repotting on a calendar is less reliable than reading the plant. For cushion sandwort, 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 cushion sandwort

Every 2–3 years, into bone-dry mix. Cushion Sandwort's growth habit — cushion-forming, densely compact perennial; extremely slow-growing — sets the pace. Cushion Sandwort is a tight cushion-forming alpine perennial native to the mountains of Spain and southern France. It produces tiny white flowers in late spring above dense, compact mounds of overlapping leaves. A classic choice for alpine troughs, scree gardens, and rock crevices; demands perfect drainage and full sun to thrive.

What size pot to step cushion sandwort up to

Use a pot only one size up — or even the same pot with fresh gritty mix if the roots have room. Cushion Sandwort 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 cushion sandwort

Spring or summer, while cushion sandwort 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 cushion sandwort

Repot dry. Do not water cushion sandwort 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 very gritty, alkaline to neutral, extremely free-draining 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 cushion sandwort 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 cushion sandwort 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 cushion sandwort

Cushion Sandwort wants very gritty, alkaline to neutral, extremely free-draining. Best in a mix of limestone grit and loam (70:30). pH 6.5–8.0. Plant in rock crevices with roots going deep into cool, mineral soil. Ideal for alpine house or trough culture. Never use peat-based composts. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting cushion sandwort — frequently asked questions

How often should you repot cushion sandwort?

Every 2–3 years, into bone-dry mix for cushion sandwort. Repot cushion sandwort every 2–3 years into a snug pot of very gritty, alkaline to neutral, extremely free-draining, 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 cushion sandwort need?

When is the best time of year to repot cushion sandwort?

Should you water cushion sandwort after repotting?

No — not straight away. Repot cushion sandwort 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 cushion sandwort after repotting?

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