Petrocosmea grandiflora Helmsl.

RHS Plant Profile

large-flowered petrocosmea

Alpine Rockery

An alpine herbaceous perennial up to 6cm high, with an almost flat rosette of rounded, felted succulent green leaves, and many white, lavender-tinged or lavender-blue flowers 2-3cm across in late winter or spring

Position

Partial shade

Soil Types

Chalk, Loam, Sand

Max Height

Up to 10 cm

Max Spread

0.1-0.5 metres

Size

Time to Maturity: 2–5 years
Max Spread: 0.1-0.5 metres
Max Height: Up to 10 cm

Growing Conditions

Chalk Loam Sand

Moisture: Well–drained
pH: Alkaline or Neutral

Position

Partial shade

Aspect: West–facing or East–facing or South–facing
Exposure: 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): H2

Colour & Scent

Season	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family: Gesneriaceae
Native to GB/Ireland: No
Foliage: Evergreen
Habit: Matforming
Genus: Petrocosmea are evergreen perennials producing low rosettes of fleshy, often felted, lance-shaped or rounded leaves. Five-lobed, tubular to bell-shaped flowers are produced in small clusters in spring
Name Status: Correct
Plant Range: China (Yunnan)

How to Grow

Cultivation

Grow in a cold greenhouse or alpine house, in indirect light, in a shallow pot of very well-drained, peat-free, loam-based compost with added grit and leafmould; water moderately while growing, and sparingly in winter, and always keep water off the leaves; in frost-free climates, grow in shade in vertical crevices in walls or rock gardens so that rain will drain away

Propagation

Propagate by seed sown as soon as it is ripe, or by leaf cuttings in summer and autumn

Suggested planting locations and garden types

Patio and container plants

Pruning

No pruning required

Pests

May be susceptible to slugs, snails, aphids, glasshouse whitefly, mealybugs, scale insects and tarsonemid mites

Diseases

May be susceptible to mildew and by crown, leaf, stem and root rots