Helianthemum Plant Growing & Care Guide for Gardeners
Article by Dean Ravenscroft, Ph.D. - Updated 19th Oct 2023
In this Gardener's HQ guide, we'll explore cultivating Helianthemum plants in your garden, indoor spaces, and other settings.
- Plant Characteristics: Helianthemum plants showcase colorful, saucer-shaped flowers that can brighten any garden. They can be perfect for rock gardens, walls, or sandy areas due to their low-growing nature.
- Ideal Growing Conditions: Thrives in full sun with a well-draining soil. Use a soil that has slightly alkaline to neutral pH level.
- General Care: While drought-tolerant once established, it's best to water young plants regularly. Pruning after flowering will help maintain a compact shape.
- Tips for New Gardeners: Helianthemum has a hardy nature, and is resistant to most pests. Ensure good drainage to avoid root rot.
Sun Rose, and Rock Rose: Cultivation & Garden Use
Plants of the Helianthemum plant genus are half hardy or hardy perennials that have a shrubby nature.
They usually reach a height of about 10 to 12 inches (25-30 cm). This makes them ideal for use in rock gardens. They are also great for filling the gaps between stones in dry stone walls and for use in paving. As many species spread wider than they grow tall, they can also be handy as ground cover or at the front of a border,
Helianthemum syriacum by ch.deff.
The foliage of Helianthemum Plant is silver or green in color. Plants come into flower from spring to autumn (species specific) with flowers of orange, scarlet, yellow or bronze.
Some of the common names for Helianthemum include Sun Rose, Rock Rose and Frostweed.
Species Specific Grow Guide for Helianthemum nummularium.
How to Grow Sun Rose (and other Helianthemum)
Helianthemum plants can be grown directly outside by sowing seeds on the soil surface in late autumn, or before the first frost of spring.
Sun Roses (and other Helianthemum), as per the name, like to grow in sunny areas of the garden.
It is very important that the soil they grow in has good drainage, but the quality of the soil is not as important.
If you plan to start growing Helianthemum seedlings indoors, then they should be prepared about eight weeks in advance. Put the Helianthemum plant seedlings out into the garden following the last frost of spring.
It usually takes them about three weeks to germinate. This should be done at a temperature of 21 to 24 degrees centigrade (70 to 75°F).
Helianthemum almeriense by Peter M Greenwood.
Caring for Sun Rose - Helianthemum plants in the Garden
Helianthemum Care: If you require more sun roses / Helianthemum plants in the garden, then simply take cuttings at the end of summer.
Unfortunately, members of the Helianthemum genus are not the easiest plants to look after: they have short lived flowers that should be removed once they have finished blooming.
Once the flowering has completed, it is best to then cut back about a third of the plant; so that it becomes shapely; this may also lead to a second bloom.
Commonly Grown Helianthemum Species
Helianthemum nummularium
Helianthemum nummularium (Common Rock-rose), photograph by Ragnhild&Neil Crawford; CC.
Helianthemum canadense
Helianthemum canadense (Longbranch Frostweed / Canada Frostweed / Rock frost / Frostplant), picture by Aaron Carlson; CC.
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Helianthemum Growing and Care Guide
Common Names: Rock Rose, Sun Rose, Frostweed, Rush Rose.Life Cycle: Hardy perennial. Half hardy perennial.
Height: 6 to 18 inches (30 to 45 cm).
Native: Northern Hemisphere.
Family: Cistaceae.
Growing Region: Zones 6 to 9.
Flowers: Species dependent: Spring and/or summer and/or autumn.
Flower Details: White, orange, yellow, scarlet, bronze. Five petals. Bi-colored. Saucer-shaped.
Foliage: Evergreen. Silver, Green. Opposite. Oval.
Sow Outside: Surface. Start of spring - before the last frost, or towards the end of autumn. Spacing 5 to 18 inches (12 to 45 cm).
Sow Inside: Germination time: two to three weeks. Temperature: 70 to 75°F (21 to 24°C). Six weeks to two months before the last expected frost. Transplant outdoors following the last frost.
Requirements and care: Full sunlight. Good drainage. Poor soil, chalky soil. Can survive in dry soils. Flowers bloom for just a day, so remove the fading ones regularly.
Cut back to two/thirds size once the first round of blooming has completed to encourage a second round of flowering.
Propagate: cuttings can be taken towards the end of summer.
Miscellaneous: Stamens are touch sensitive.
Common Questions
How many members does the Helianthemum genus have?
The Helianthemum genus comprises about 110 species, offering a great variety of colorful options for gardens.
Do members of Helianthemum make a good garden or landscaping plant?
Yes, Helianthemum species, known as Rock Roses, are excellent choices for rock gardens and landscapes due to their hardiness and beautiful flowers.
Which Helianthemum species are most frequently grown by gardeners?
The Helianthemum nummularium, commonly known as Common Rock Rose, is frequently chosen by gardeners for its bright yellow blooms.
Are members of the Helianthemum plant genus fragrant?
While not particularly known for their scent, Helianthemum species are adored for their abundant and vibrant blooms.
What is the perfect location to grow Helianthemum?
Helianthemum thrives in sunny, well-drained spots. They're great for rockeries, borders, and gravel gardens.
Is Helianthemum invasive in the USA, if so in which states?
Presently, Helianthemum is not listed as invasive in the USA.
How do I remove Helianthemum plants from my garden?
To remove Helianthemum plants, dig up the plant ensuring to remove as much of the root system as possible to prevent regrowth.
Summary
The Helianthemum genus, part of the Cistaceae family, includes shrubs and perennials commonly known as Rock roses. Native to the Mediterranean and Middle East, they are cherished for their bright, rose-like flowers and evergreen foliage. Helianthemum nummularium is one commonly cultivated species.
Helianthemum should be planted in well-drained soil under full sun. It is drought-tolerant and thrives in poor, sandy, or gravelly soils, making it an excellent choice for rock gardens. Propagation is typically achieved through seeds or cuttings in late spring or early summer.
I hope that you enjoyed this guide on how to grow Helianthemum plants. You may also enjoy the following Gardener's HQ growing guides: How to grow Rock Rose; Purple Rock Cress, Rock Purslane, and Rhodohypoxis plants.
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