Snow-in-summer

Snow-in-summer: how do you recognise it?

Habit

Creeping, mat-forming plant 15–20 cm high that spreads to 60 cm and more by rooting stems.

Leaves

Narrow and lance-shaped, 1–3 cm long, densely covered in white woolly hairs; silver-grey and evergreen.

Flower

White stars 1.5–2 cm across with five deeply notched petals, in loose clusters above the foliage, in May–June.

Fruit

A small, slightly curved capsule like a little horn; hence the name Cerastium.

Roots

Shallow, with creeping stems that root wherever they touch the soil.

Flowering: May–June · Plants: March–April and September–October · Pruning: June–July

Why grow it?

• A silver-grey carpet that gives colour all year round, even in winter.
• In May and June, a sea of white flowers that attracts bees and hoverflies.
• Grows where little else will: poor sandy soil, between stones, on walls and banks.
• Tolerates drought and heat and needs hardly any water once established.
• Covers the ground quickly and so keeps weeds down in dry, sunny spots.

Snow-in-summer: where does it grow best?

• Full sun; in shade it becomes loose and floppy and flowers poorly.
• Poor, free-draining sandy soil or loam, acid to chalky. Also in gravel, between stones and in wall crevices.
• Dry soil: heavy, wet soil in winter makes it rot.
• Allow 40–60 cm per plant. It spreads quickly, so keep it away from small, slow rock plants.

Light

Sun

Soil type

Sand or loam

Acidity

Not fussy

Moisture

Dry

Size

0.2 m tall, 0.6 m wide

Hardiness

Hardy (to -35 °C)

Goes well with

• Lavender: The same sun and dry soil; purple beside silver and white.
• Bearded iris: Upright leaves and large flowers above the silver carpet, in May–June.
• Catmint: Blue flowers and grey leaves in the same dry spot.
• Ornamental onion: The round flower heads rise nicely above the low mat.
• Stonecrop: Takes over the flowering in late summer in a dry spot.

Snow-in-summer: when and how to plant it?

Plant in March–April and September–October.

1. Plant in March–April or in September–October.
2. Loosen the soil and mix coarse sand or gravel into heavy soil for good drainage. Do not feed.
3. Set the plant at the same depth as in the pot, no deeper: the base of the stems rots easily.
4. Space plants 40–50 cm apart; for a carpet that closes quickly, allow 4–6 plants per m².
5. Water after planting, then for the first few weeks only in dry weather.
6. Do not mulch with bark or compost: a thin layer of gravel around the base keeps the plant dry.

Care

Water

Only in the first year during long dry spells. After that it looks after itself; too much water makes it floppy and prone to rot.

Feeding

Not needed. In rich soil it grows more lushly but becomes untidy and flowers less.

Cutting back

After flowering, cut the flower stems and some of the foliage back hard; this keeps the mat dense and silvery.

Keeping it in check

In spring or after flowering, chop off runners that go too far before it smothers its neighbours.

Clearing leaves

In autumn, remove fallen leaves from the mat, otherwise it rots underneath.

Tip: Plant it on top of a low wall or along an edge where it can tumble down: that is where it looks best and where it gets in the way of smaller plants least.

Snow-in-summer: when to prune it?

Pruning months: June–July.

When: Straight after flowering, in late June or in July. Otherwise there is little pruning to do.

How:

• Shear off the spent flower stems and the top growth with shears or a hedge trimmer, just above the dense mat.
• It soon makes fresh silver-grey foliage, the carpet stays compact and it does not self-seed.
• In spring, cut out bare, woody or dead patches.
• Trim back runners that spread over paths or other plants.

Caution: Do not prune in late autumn: the mat should go into winter with its leaves.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In March–April or in September: dig a rooted piece from the edge of the mat with a spade and replant it elsewhere. It almost always succeeds.

Cuttings

In June–July, after flowering: 5 cm cuttings from non-flowering shoots in a mix of sand and potting compost. They root within a few weeks.

Snow-in-summer: how does it get through the winter?

Hardy to −35 °C.

• Very hardy, to about −35 °C: frost is not a problem in Belgium.
• Wet soil is the real enemy: choose a free-draining spot, on a slope or between stones.
• The silver foliage stays through winter, although it can look a little dingy after a wet winter.
• In a pot or trough: use a gritty mix and move it under an overhang during prolonged rain.

Diseases and pests

• Spreading: It quickly smothers small rock plants and spreads over paths. Cut back the edge every year.
• Rot and bare patches: The centre turns brown and bare, often after a wet winter or on heavy soil. Cut out dead parts, scatter some gravel and let the edge fill back in, or renew it from cuttings.
• Floppy and open: Too much shade, water or fertiliser. Give it a sunny, poor spot and cut it back after flowering.
• Grey mould: Grey fluff on the leaves in wet, mild weather or under fallen leaves. Remove affected parts and keep the soil airy and dry.

Through the year

• March: Cut out dead patches. Plant and divide.
• April: Plant. Keep the runners in check.
• May: Flowering: white stars above the silver foliage.
• June: Flowering. Cut back after flowering.
• July: Cut back if not done yet. Take cuttings.
• August: Water only young plants during long dry spells.
• September: Plant and divide.
• October: Plant. Remove fallen leaves from the mat.
• November: Keep the mat clear of leaves.
• December: Rest; the silver foliage stays.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• The name Cerastium comes from the Greek ‘keras’, horn, after its slightly curved seed capsules.
• The dense white hairs reflect sunlight and reduce water loss: that is how it survives heat and drought.
• It is related to field mouse-ear, a native plant of verges and dry grassland.