A low growing mat forming perennial, commonly grown as an edging plant or as ground cover in a rock or scree garden. A very robust and drought tolerant species that has attractive grey foliage, covered with myriads of white flowers all summer.
Family: Caryophyllaceae (pink family)
Botanical Name: Cerastium
Common Names: Snow in summer, dusty miller, Jerusalem star.
Foliage: Silver/grey simple hairy leaves. Evergreen.
Flowers: White, star-shaped, 5-petalled flowers, with notched petals.
Flowering Period: Late spring to early summer.
Soil: Well-drained soil (chalk, clay, sand or loam). Any pH. Thrives in poor soils.
Conditions: Full sun. South or west-facing aspect, in an exposed or sheltered position.
Habit: Spreading, mat-forming.
Type: Annuals or perennials.
Hardiness: Fully hardy in all of the UK (down to -20)
Plant in an open sunny site in poor soil of low fertility. Suitable for sunny banks, large rock gardens and scree or gravel beds.
Cerastium is vigorous spreader, which can become highly invasive to the detriment of all other plants, therefore it is best grown in an area where it can easily be kept in check.
Protect from winter wet. Do not over-feed plants or they will become straggly and not flower so well.
Snip off faded blooms and trim the plants back by a third or so at the end of the season to rejuvenate them. To prevent overspreading, dig up and remove any sections of the plant that are growing outside their allotted area.
Generally pest and disease free.
Propagate by seed, division or stem tip cuttings.
A few varieties are available in the UK, including:
C. aipinum lanatum (woolly snow in summer) is a slow-growing alpine form with silvery, grey-green, hairy leaves and white flowers on short stems. Height to 2in (5cm).
C. biebersteinii a slightly taller form, with greyish-green leaves and white flowers in May-June. Height to 8in (20cm).
C. tomentosum is a vigorous low spreading form with star-shaped white flowers in June-July. Height to 6in (15cm). Several named hybrids are available.