Common Name: rock rose
Type: Herbaceous perennial
Family: Cistaceae
Native Range: Western Asia, Europe
Zone: 5 to 7
Height: 0.50 to 1.00 feet
Spread: 2.00 to 3.00 feet
Bloom Time: May to June
Bloom Description: Pastel pink or yellow
Sun: Full sun
Water: Dry
Maintenance: Medium
Suggested Use: Ground Cover, Naturalize
Flower: Showy
Tolerate: Drought
Culture
Best grown in dry, alkaline, rocky or sandy, well-drained loams in full sun. Foliage is evergreeen, but plants are not reliably winter hardy throughout USDA Zone 5 where they appreciate a winter mulch (preferably a cover of evergreen boughs). Plants prefer cool summers and warm winters, which makes them less than ideally suited for the St. Louis climate. Shear plants after flowering to shape and to encourage additional growth. If grown as a ground cover, space 2-3’ apart.
Noteworthy Characteristics
Helianthemum nummularium, commonly called sun rose, is a low-growing, woody-stemmed, shrub-like plant with evergreen foliage. It typically grows 8-12” tall and spreads by creeping stems to 3’ wide. Five-petaled, rose-like flowers (to 1” diameter) bloom for up to 2 months (late spring to early summer) in terminal cymes. Flowers have somewhat variable coloration, but most often feature pastel yellows and pinks. Each flower opens for only one day, but in the proper growing environment, bloom can be so profuse as to cover the entire plant to the point of obscuring the foliage. Grayish-green, lance-shaped leaves (1-2” long).
Genus name comes from the Greek words helios meaning the sun and anthemon meaning meaning a flower.
Specific epithet means resembling a coin.
Problems
No serious insect or disease problems. Rots easily in poorly-drained soils.