Helianthemum nummularium subsp. glabrum

Synonyms

Helianthemum oelandicum subsp. alpestre 'Serpyllifolium'
Helianthemum alpestre serpyllifolium
Helianthemum serpyllifolium

Alpine Rockery Shrubs

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A low-growing, spreading evergreen shrub to around 40cm in height with small, mid-green linear leaves. Masses of small, single, yellow flowers appear in late spring to summer

Position

Full sun

Soil Types

Chalk, Clay, Loam, Sand

Max Height

0.1-0.5 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity: 2–5 years
Max Spread: 0.1-0.5 metres
Max Height: 0.1-0.5 metres

Growing Conditions

Chalk Clay Loam Sand

Moisture: Well–drained
pH: Alkaline or Neutral

Position

Full sun

Aspect: East–facing or South–facing or West–facing
Exposure: Exposed or Sheltered
Hardiness

Hardiness Ratings

All ratings refer to the UK growing conditions unless otherwise stated. Minimum temperature ranges (in degrees C) are shown in brackets

H1A: under glass all year (>15C)
H1B: can be grown outside in the summer (10 - 15)
H1C: can be grown outside in the summer (5 - 10)
H2: tolerant of low temperatures, but not surviving being frozen (1 to 5)
H3: hardy in coastal and relatively mild parts of the UK (-5 to 1)
H4: hardy through most of the UK (-10 to -5)
H5: hardy in most places throughout the UK even in severe winters (-15 to -10)
H6: hardy in all of UK and northern Europe (-20 to -15)
H7: hardy in the severest European continental climates (< -20): H4

Colour & Scent

Season	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family: Cistaceae
Native to GB/Ireland: No
Foliage: Evergreen
Habit: Bushy
Genus: Helianthemum are bushy or spreading evergreen shrubs with small paired leaves and saucer-shaped flowers borne in short racemes in spring and early summer
Name Status: Correct

How to Grow

Cultivation

Grow in fertile, neutral to alkaline, moist but well-drained soil in full sun. Suitable for rock garden or the front of a border, or as a groundcover on a sunny bank. This plant was included in the RHS Helianthemum (rock rose) trial 2024-2026 https://www.rhs.org.uk/plants/trials-awards/ongoing-plant-trials/helianthemum

Propagation

Propagate by softwood cuttings in late spring or early summer

Suggested planting locations and garden types

City and courtyard gardens
Cottage and informal garden
Gravel garden
Patio and container plants
Rock garden
Banks and slopes
Flower borders and beds
Ground cover

Pruning

See pruning group 10, after flowering

Pests

Generally pest-free

Diseases

May be susceptible to honey fungus in gardens where it is present but insufficient data to determine degree of susceptibility