Geranium maderense 'Guernsey White'

RHS Plant Profile

giant herb robert 'Guernsey White'

Herbaceous Perennial Annual Biennial Conservatory Greenhouse

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A large evergreen biennial or short-lived perennial, up to 1.2m high, with rosettes of finely divided, fernlike glossy green leaves up to 60cm long. Masses of flat white flowers, with dark pink central eyes, are produced on tall, branching stems in early summer

Position

Full shade, Full sun, Partial shade

Soil Types

Chalk, Loam, Sand

Max Height

1-1.5 metres

Max Spread

1-1.5 metres

Size

Time to Maturity: 1–2 years
Max Spread: 1-1.5 metres
Max Height: 1-1.5 metres

Growing Conditions

Chalk Loam Sand

Moisture: Moist but well–drained or Well–drained
pH: Acid or Alkaline or Neutral

Position

Full shade Full sun Partial shade

Aspect: East–facing or North–facing or South–facing or West–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): H3

Colour & Scent

Season	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family: Geraniaceae
Native to GB/Ireland: No
Foliage: Evergreen
Habit: Bushy, Clump forming
Genus: Geranium can be annuals, biennials and perennials, herbaceous or evergreen, with rounded, usually palmately lobed or divided leaves, and lax inflorescences of rounded, 5-petalled flowers
Name Status: Accepted

How to Grow

Cultivation

In milder areas, grow outdoors in well-drained soil; may benefit from afternoon shade in hot summers. In areas prone to frosts, grow under glass in peat-free, loam-based compost with added sharp sand in bright filtered light. Flowers are produced in the second or third year; after flowering the plant sets seed and dies

Propagation

Propagate by seed, sown in late winter or early spring at 21-23°C

Suggested planting locations and garden types

Cottage and informal garden
Gravel garden
Mediterranean climate plants
City and courtyard gardens
Coastal
Wildlife gardens
Conservatory and greenhouse
Flower borders and beds

Pruning

No pruning required. Avoid cutting older leaf stems as they bend downwards; these often serve to support the plant when in flower

Pests

May be susceptible to vine weevil, geranium sawfly, slugs and snails

Diseases

May be susceptible to powdery mildews, downy mildews, rust diseases and virus diseases