Helianthemum — commonly called sun rose or rock rose–includes both species and many hybrid sub-shrubs grown for their bright and pastel blooms above gray foliage. Helianthemum grows well in average soil and thrives even in dry soil making it a colorful ground cover for banks and sun-drenched beds.
Helianthemum blooms from late spring into summer. Each flower lasts just one day but produce flower after flowers keeping the garden colorful. Flower colors include flame red, apricot, orange, yellow, pink, rose peach, salmon, and white. Plants can be sheared back to renew growth and prolong the flowering season.
Helianthemum grows well in rock gardens, seashore gardens, in dry beds, and on sunny patios.
The Helianthemum genus includes about 110 evergreen or semi-evergreen species and many cultvars.
Get to Know Helianthemum
- Plant type: Evergreen or semi-evergreen shrublet
- Growing zones and range: Zones 6 to 8
- Hardiness: Hardy to Zone 6
- Height and width: 4 to 20 inches (10-51cm) tall and about half as wide depending on the variety.
- Foliage: Elliptic leaves .5 to 1 inch (1-2.5cm) long; some may be glossy green above and fuzzy gray beneath, while others may be gray on both sides.
- Flowers: Rose-like blossoms are inch (2.5cm) wide single or double flowers in bright or pastel colors—flame red, apricot, orange, yellow, pink, rose, peach, salmon, or white; each flower has five petals and lasts only a day, but new buds continue to open so that the budding period lasts several weeks.
- Bloom time: Spring to midsummer; may bloom again later if cut back after the first bloom.
- Uses: Front of borders, along paths, or in a rock garden; excellent ground cover on dry sunny banks where they will not be subject to winter wet collecting around their stems and roots.
- Garden companions: Sea thrift (Armeria maritima), rock soapwort (Saponaria ocymoides)
- Common name: Sun roses, rock roses
- Botanical name: Helianthemum
- Family name: Cristaceae
- Origin: North and South America, Asia, Europe
Where to Plant Helianthemum
- Plant Helianthemum in full sun.
- Plant Helianthemum in light, dry, somewhat alkaline soil. Plants will grow best if given soil that is not too rich.
When to Plant Helianthemum
- Set container-grown Helianthemum in the garden in spring or autumn.
- Sow seeds in spring.
Planting and Spacing Helianthemum
- Plant Helianthemum 2 to 3 feet (.6-1m) apart.
- Sow Helinthemum seed 1/8 inch deep in evenly prepared soil.
How to Water and Feed Helianthemum
- Give Helianthemum moderate water. Mature plants can tolerate dry soil.
- Fertilizer Helianthemum in spring with an all-purpose organic fertilizer.
How to Care for Helianthemum
- Helianthemum does best if severely cut back after blooming; this will trigger new growth and new blooms.
- Helianthemum benefits from winter protection in northern areas.
- In cold winter areas, lightly cover plants with branches from evergreens in winter to keep foliage from dehydrating.
Helianthemum Pests and Diseases
- Helianthemum commonly do not experience diseases or pests.
- Divide Helianthemum in early summer.
- Take Helianthemum softwood cuttings in early summer.
- Sow seeds in containers and grow on in a cold frame after seeds ripen.
Helianthemum Varieties to Grow
- Helianthemum apenninum, ‘Roseum’, with comparatively large, pink flowers that contrast nicely with the gray, furry foliage.
- H. nummularium hybrids differ in foliage grayness and flower color. Cultivars include: ‘Brunette’ bears green leaves and dark orange flowers.d
- H.‘Buttercup’ has golden-yellow flowers and grows to 1 foot (.3m) tall.
- H.‘Fire Dragon’ is coppery red. 8-12 inches (2.4-3.7m) tall.
- H. ‘Mesa Wine’ has dark green leaves and dark red flowers.
- H. ‘Orange Surprise’ is pale orange. 4 inches (10cm) tall.
- H. ‘Raspberry Ripple’ has white blooms with purple centers. 8 inches (20cm) tall.
- H. ‘Saint Mary’s’ has dark green leaves and white flowers.
- H. ‘Stoplight’ features grayish-green leaves and red flowers.
- H. ‘Wisley Pink’ produces gray foliage and pink flowers.
- H. ‘Wisley Primrose’ has gray-green foliage and pale yellow flowers.
- H. ‘Wisley White’ bears creamy-white flowers with prominent yellow centers in mid-to-late summer and grows to 1 foot (.3m) tall.