Dodecatheon jeffreyi

RHS Plant Profile

giant American cowslip

Other common names

giant American cowslip, sierra shooting star

Synonyms

Dodecatheon tetrandrum, Primula jeffreyi

Herbaceous Perennial Alpine Rockery

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A herbaceous perennial up to 60cm high, with a basal rosette of oval, mid-green leaves that are slightly sticky. Pendent flowers, in shades of pink, purple and red and with distinctive swept-back petals, are held on short stalks from the top of stout flowering stems in early to mid summer

Position

Full sun, Partial shade

Soil Types

Chalk, Clay, Loam

Max Height

0.5-1 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity: 2–5 years
Max Spread: 0.1-0.5 metres
Max Height: 0.5-1 metres

Growing Conditions

Chalk Clay Loam

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

Position

Full sun Partial shade

Aspect: East–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): H5

Colour & Scent

Season	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family: Primulaceae
Native to GB/Ireland: No
Foliage: Deciduous
Habit: Clump forming
Genus: Dodecatheon are summer-dormant herbaceous perennials with basal rosettes of simple leaves and erect or arching stems bearing umbels of cyclamen-like flowers with strongly reflexed petals
Name Status: Correct

How to Grow

Cultivation

Grow in moist but well-drained, humus rich soil in sun or part shade. Needs plenty of moisture while in growth; ideal for planting in a woodland or near a pond or stream

Propagation

Propagate by seed, sown in pots in an open frame as soon as ripe, or by division in spring. Seed needs exposure to cold before it will germinate

Suggested planting locations and garden types

Cottage and informal garden
Underplanting of roses and shrubs

Pruning

No pruning required

Pests

May be susceptible to slugs and snails on young growth

Diseases

Generally disease-free