Common Name: snow-in-summer
Type: Herbaceous perennial
Family: Caryophyllaceae
Native Range: Italy, Sicily
Zone: 3 to 7
Height: 0.50 to 1.00 feet
Spread: 0.75 to 1.00 feet
Bloom Time: June
Bloom Description: White
Sun: Full sun
Water: Dry
Maintenance: Medium
Suggested Use: Ground Cover, Naturalize
Flower: Showy
Leaf: Colorful
Tolerate: Deer, Drought, Dry Soil, Shallow-Rocky Soil
Culture
Best grown in dry, sandy, well-drained soils in full sun. Tolerates a somewhat wide range of soils except poorly-drained ones which inevitably lead to root rot. Grows well in cool summer climates. Plants are winter hardy to USDA Zone 2. Intolerant of the high summer heat and humidity of the deep South. Spreads by runners to fill in areas, but is not considered to be invasive in the hot St. Louis climate where it is less robust than in cooler northern climates. Plants will self-seed in the garden if spent blooms are not removed. Best to shear off flower stems after bloom in order to prevent self-seeding, reduce future foliage decline, and shape/neaten the foliage mat. Large beds can be mowed on a high setting. Divide every year if needed to help maintain compact size of the mat. Starter plants may be planted 9-12” apart to quickly cover large areas.
Noteworthy Characteristics
Cerastium tomentosum, known as snow-in-summer, is a short-lived, low-growing, mat-forming perennial which is typically massed in sunny locations as a ground cover. Tufts of narrow, gray-green leaves (each to 1" long and 1/4" wide) form a 6” tall foliage mat. Leaves are evergreen. In late spring, flower stems rise above the foliage mat (typically to 8-12”) carrying clusters (cymes) of white blooms which form a snow-like carpet (hence the common name). Flowers (to 1” diameter) have 5 notched petals and are similar in appearance and closely related to several of the chickweeds. Less invasive, more compact cultivars of this species usually make better garden plants.
Genus name comes from the Greek word keras meaning horn in reference to the seed capsule which in some species is bent slightly like a cow’s horn.
Specific epithet is in reference to the plant's woolly white leaves and stems.
Problems
No serious insect or disease problems. Damping off may occur in climates with high humidity or locations with too much shade. Root rot can be a serious problem if plants are grown in poorly-drained soils or in soils that remain wet. Plants are short-lived, and dead patches often begin to appear after several years. In St. Louis, foliage usually declines as the summer progresses.
Uses
Ground cover for sunny areas. Rock gardens, border fronts, cottage gardens, edgings, bulb cover or dry stone wall planting pockets.