Repotting guide

When & how to repot Snow-in-Summer (Cerastium tomentosum)

Also called Snow-in-Summer, Mouse-ear Chickweed.

More about snow-in-summer

About Snow-in-Summer

Cerastium tomentosum · also called Snow-in-Summer, Mouse-ear Chickweed · flowering

A fast-spreading, silver-white-leaved ground cover in the family Caryophyllaceae, producing a dense carpet of white, five-petalled flowers in late spring and early summer. Its woolly, silver foliage makes it visually striking year-round. Extremely drought-tolerant and hardy, it suits rock gardens, slopes, and dry walls — but can become invasive if not managed.

Mature size: 15–25 cm tall, 60–90+ cm wide

Watch for — Root and crown rot: Despite its toughness, it is susceptible to rot in heavy, wet soils or with overwatering. Ensure sharp drainage and avoid planting in low-lying areas where water pools. Once crown rot takes hold, affected sections should be cut out and the soil improved.

How to tell snow-in-summer needs repotting

Repotting on a calendar is less reliable than reading the plant. For snow-in-summer, 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 snow-in-summer

Every 2–3 years, into bone-dry mix. Snow-in-Summer's growth habit — vigorous, spreading, mat-forming semi-evergreen perennial — sets the pace. A fast-spreading, silver-white-leaved ground cover in the family Caryophyllaceae, producing a dense carpet of white, five-petalled flowers in late spring and early summer. Its woolly, silver foliage makes it visually striking year-round. Extremely drought-tolerant and hardy, it suits rock gardens, slopes, and dry walls — but can become invasive if not managed.

What size pot to step snow-in-summer up to

Use a pot only one size up — or even the same pot with fresh gritty mix if the roots have room. Snow-in-Summer 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 snow-in-summer

Spring or summer, while snow-in-summer 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 snow-in-summer

Repot dry. Do not water snow-in-summer 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 well-drained, poor to lean, sandy or gritty soil 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 snow-in-summer 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 snow-in-summer 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 snow-in-summer

Snow-in-Summer wants very well-drained, poor to lean, sandy or gritty soil. Thrives in poor, dry, stony soils where other plants struggle. Fertile, moisture-retentive soils cause overly vigorous, floppy growth and increase rot risk. Lime-tolerant; pH 6.0–8.0. Amend clay soils heavily with grit. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting snow-in-summer — frequently asked questions

How often should you repot snow-in-summer?

Every 2–3 years, into bone-dry mix for snow-in-summer. Repot snow-in-summer every 2–3 years into a snug pot of very well-drained, poor to lean, sandy or gritty soil, 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 snow-in-summer need?

When is the best time of year to repot snow-in-summer?

Should you water snow-in-summer after repotting?

No — not straight away. Repot snow-in-summer 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 snow-in-summer after repotting?

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