Rock rose
Helianthemum nummularium ·
A low, woody, evergreen mat covered in papery, saucer-shaped flowers in yellow, orange, pink, red or white in early summer. Each flower lasts a day.
- Size
- 10 in tall, 24 in wide
- Zones
- 5 to 8
- Light
- Full sun
- Flowers
- Late May to early July
- Pets
- Not checked
- Job in a bed
- Carpet
A bed built around rock rose
The planner designed this bed around rock rose when this page was made: a 12 × 6 ft (3.7 × 1.8 m) English border in zone 6, full sun. It chose the other plants from the 715 that suit those conditions and its dry soil, and says below why rock rose stands where it does.
The plants
- 1 Rock rose × 8, yellow
- 2 October daphne × 7, pink
- 3 Little bluestem 'The Blues' × 3, tan
- 4 False sunflower 'Summer Nights' × 3, yellow
- 5 Silver sage × 1, silver leaves
- 6 Wild lupine × 8, blue
- 7 Ornamental onion 'Purple Sensation' × 4, purple
- 8 Spring starflower × 12, blue
Why this plant
- The only open bowls. The others are dense clusters, spires, daisies and others. Shape reads at a distance, where colours blur.
Why here
- Under the taller plants. It runs back between them as living mulch: there its job is to cover the soil, not to be looked at.
- 8 plants in 2 groups (5 and 3). Seen again further along, the same plant ties the bed together.
- Fine leaf against bold. Silver sage is beside it: the strongest contrast of leaf there is.
Why now
- In flower for 7 weeks. From late May to early July.
- Part of the bed's peak. With wild lupine and ornamental onion 'Purple Sensation' in late May: 3 kinds at once. No week has more.
- The only leaves in winter. From November to March it is what there is to look at.
Planned as an English border: 5 of the 7 groups (71%) are drifts, longer along the bed than they are deep. The scheme leans cool (pink, blue and purple) and uses yellow for warmth, with tan to calm things between them. The most in flower at one time is 3 kinds, from late May.
The planner's own design check: 15 Excellent, 2 Good. It flags one thing to watch: Nothing on this plan is highly poisonous or an aggressive spreader.
Open this bed in the planner Change its size, the sun or the style, move plants about, or swap one for another.
Where rock rose goes in a border
At 10 in it belongs at the front of a bed. In the planner's ten height classes it is low (6 to 12 in).
Its job: carpet. A groundcover planted in threes and fives to cover the soil: along the front, and just behind it.
A Mediterranean subshrub for the driest, sunniest edge. Shear it lightly after flowering to keep it dense. Wet soil and humid summers shorten its life.
- Sunny banks and wall tops
- Rock gardens
- Hot, dry front edges
What to plant with rock rose
Plants recorded as good partners for it, and what each pairing does:
- English lavender 'Hidcote': purple against yellow, opposite each other on the colour wheel, if you choose those colours, in flower together for three weeks; spires rising out of its mound; tall enough (18 in) to stand behind it.
- Creeping thyme: purple against yellow, opposite each other on the colour wheel, if you choose those colours, in flower together for five weeks; low enough (3 in) to stand in front of it; happy in the same dry soil.
- Blue fescue: its blue-green leaves are a setting for the flowers, before and after; happy in the same dry soil.
Questions about rock rose
Does rock rose need sun or shade?
Rock rose grows in full sun (6 or more hours of direct sun a day).
It wants dry, sharply drained soil, on the lean side, with no feeding, and little watering once settled.
What zones does rock rose grow in?
USDA zones 5 to 8. It is hardy to zone 5, which means it survives winter nights down to about −10 °F (−23 °C).
Above zone 8 it struggles: the zones measure winter cold, but a plant's top zone usually means the summers are too hot or the winters too mild for it to rest.
Gardening in Canada? Use the USDA zone for your town: Canada's own zone map uses different numbers.
When does rock rose flower in my zone?
In zone 5 it flowers late May to early July. As a spring flower it moves about a week for every zone: earlier where it is warmer, later where it is colder.
| Zone 5 | Late May to early July |
|---|---|
| Zone 6 | Mid May to early July |
| Zone 7 | Early May to late June |
| Zone 8 | Early May to late June |
Worked out from Hopkins' bioclimatic law: spring arrives about four days later for each degree of latitude north, and one zone is roughly two degrees. A warm spring or a cold one moves any garden two weeks either way.
How far apart should rock rose be planted?
18 in (45 cm) apart, from the middle of one plant to the middle of the next. That is a little closer than its full width of 24 in (60 cm), so a group knits into one patch.
It grows 10 in (25 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many rock rose plants do I need?
At 18 in apart, set out in staggered rows:
- 5 to fill 10 square feet (about 1 m²)
- 7 for a single row 10 ft (3 m) long
- 17 to fill a 4 × 8 ft bed on its own
In a mixed border, plant it as threes and fives, along the front and just behind it.
In the bed above, the planner used eight in two groups.
Is there a native plant like rock rose?
Rock rose is not native to North America. These North American natives come closest to doing its job:
- Woolly yarrow: the same job in a bed, the same flowering time and the same colour; 6 in narrower, not evergreen.
- Seaside daisy: the same job in a bed and the same size; flowers late May to late August, lavender, not yellow.
- Three-toothed cinquefoil: the same job in a bed and the same flowering time; 4 in shorter, 6 in narrower.
Matched the way the planner's Swap button matches plants: the same job in a bed, then size, then flowering time.
What flowers after rock rose?
Rock rose is over by early July. These start as it finishes and carry the same spot on, so it never goes flat:
- Black-eyed Susan: from mid July to mid September, 24 in tall.
- Butterfly weed: from late June to early August, 24 in tall.
- Daylily: from late June to early August, 2½ ft tall.
What does rock rose look like in winter?
Rock rose keeps its grey-green leaves all winter, so it is one of the plants that hold a bed together from November to March, when the perennials have gone.
More Helianthemum
- Rock rose 'Henfield Brilliant' Helianthemum 'Henfield Brilliant'
- Rock rose 'Wisley Primrose' Helianthemum 'Wisley Primrose'
In these guides
- Low plants for the front of a border
- Groundcover plants
- Evergreen perennials, ferns and grasses
- Plants for a white garden
- Silver and grey-leaved plants
Every fact on record
- Type
- Perennial (groundcover)
- Size
- 10 in (25 cm) tall, 24 in (60 cm) wide
- Plant
- 18 in (45 cm) apart
- Height class
- Low (6 to 12 in)
- Place in the bed
- Front
- Flowers
- Late May to early July; open bowls; yellow, orange, pink, red, white
- Leaves
- Fine texture, evergreen; grey-green
- Shape
- Mat-forming, clumping
- Hardy in
- USDA zones 5 to 8
- Light
- Full sun
- Soil
- Lean, dry and sharply drained
- Water
- Low
- Feeding
- None needed
Not yet checked against an outside reference: its figures rest on general horticultural knowledge. Flowering times are for zone 5: later in colder zones, earlier in warmer ones. Toxicity and spread information is a general gardening guide, not veterinary or medical advice, and invasive status varies by region. If a person or pet eats a plant, contact poison control or a vet. Check your local invasive species list before planting anything with a spread warning.