Saxifraga 'Cumulus' (7) | saxifrage 'Cumulus'

RHS

Alpine Rockery

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A dwarf perennial forming a cushion of small rosettes of tiny narrow leaves, with large white flowers held above the foliage, in spring

Position

Full sun, Partial shade

Soil Types

Chalk, Loam

Max Height

Up to 10 cm

Max Spread

0-0.1 metre

Size

Time to Maturity: 2–5 years
Max Spread: 0-0.1 metre
Max Height: Up to 10 cm

Growing Conditions

Chalk Loam

Moisture: Well–drained
pH: Alkaline or Neutral

Position

Full sun Partial shade

Aspect: West–facing or South–facing or East–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): H5

Colour & Scent

Season	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family: Saxifragaceae
Native to GB/Ireland: No
Foliage: Evergreen
Habit: Matforming
Genus: Saxifraga can be annuals, biennials, evergreen or herbaceous perennials, mostly mat-forming in habit, with simple or palmately lobed leaves and starry or rounded flowers which may be solitary of in panicles or cymes
Name Status: Accepted
Horticultural Group

Horticultural Classification Codes

Horticultural Classification Codes are often given to genera which have a large number of species or cultivars. They are used to categorise cultivated plants based on specific, shared characteristics such as shape, colour, size or flowering time, and can be displayed as letters or numbers

For example:
Dahlia ‘Sunset Kate (Sin) = Single flower
Rosa ‘Marigold’ (HT) = Hybrid Tea: Porphyrion section saxifrages are compact, cushion or mat-forming evergreen perennials with small, usually lime-encrusted leaves, and 5-petalled white, yellow or pink flowers in early summer

How to Grow

Cultivation

Grow in a moderately fertile, very well-drained, neutral to alkaline soil in light shade. A rock garden or crevice garden is ideal so as to keep the roots cool. Troughs, sinks or an alpine house are also ideal places in which to grow 'Cumulus'. Use shallow pans of two parts peat-free John Innes No 1 compost and one part limestone chippings

Propagation

Propagate by seed in autumn in containers in an open frame (don't expect cultivars to come true from seed). Individual rosettes can be detached in spring as root cuttings in late spring or early summer

Suggested planting locations and garden types

Gravel garden
Rock garden
Patio and container plants

Pruning

No pruning required. Deadhead where required

Pests

Aphids, glasshouse red spider mite and vine weevil may be problematic

Diseases

Generally disease-free