Oenothera 'Crown Imperial'

RHS Plant Profile

evening primrose 'Crown Imperial'

RHS

Synonyms

Oenothera coryi 'Crown Imperial'

Herbaceous Perennial

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An upright, clump-forming herbaceous perennial 40-50cm high with broad basal leaves and narrow, glossy, bright green stem leaves, green stems topped by clusters of flowers so that the plant looks like a small crown imperial fritillary, and flowers opening from red buds into large, bowl-shaped, vibrant yellow flowers from midsummer; the flowers are sterile so it does not self-seed

Position

Full sun

Soil Types

Chalk, Loam, Sand

Max Height

0.1-0.5 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity: 1–2 years
Max Spread: 0.1-0.5 metres
Max Height: 0.1-0.5 metres

Growing Conditions

Chalk Loam Sand

Moisture: Well–drained
pH: Acid or Alkaline or Neutral

Position

Full sun

Aspect: West–facing or South–facing or East–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): H5
Drought Resistance: Yes

Colour & Scent

Season	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family: Onagraceae
Native to GB/Ireland: No
Foliage: Deciduous
Habit: Columnar upright
Genus: Oenothera can be annuals, biennials or perennials, upright or spreading in habit, with simple or lobed leaves and bowl-shaped, white, yellow or pink flowers over a long period in summer
Name Status: Accepted

How to Grow

Cultivation

Grow in poor to moderately fertile, very well-drained soil, even stony soil, in full sun

Propagation

Propagate by internodal one-leaf softwood cuttings of unflowered shoots from late spring to midsummer, or by division in early spring

Suggested planting locations and garden types

City and courtyard gardens
Gravel garden
Prairie planting
Cottage and informal garden
Cut flowers
Flower borders and beds

Pruning

No pruning required

Pests

May be susceptible to slugs and aphids

Diseases

May be susceptible to leaf spot, powdery mildews and downy mildews; root rot may be a problem in rich, wet, heavy soil. Generally disease-free