• AGM plants

    AGM plants have been through a rigorous trial and assessment programme. They are:

    • Excellent for ordinary use in appropriate conditions
    • Available to buy
    • Of good constitution
    • Essentially stable in form & colour
    • Reasonably resistant to pests & diseases

Trillium grandiflorum

American wake-robin

AGM plants

AGM plants have been through a rigorous trial and assessment programme. They are:

  • Excellent for ordinary use in appropriate conditions
  • Available to buy
  • Of good constitution
  • Essentially stable in form & colour
  • Reasonably resistant to pests & diseases
American wake-robin

© Christopher Whitehouse

  • Other common names American wake-robin
    American wood lily

    large white wood lily
    white wake robin
    wake-robin
    snow trillium

    see more
  • Family Melanthiaceae

  • Genus Trillium are rhizomatous, herbaceous perennials with erect stems bearing a whorl of ovate or diamond-shaped leaves, with one or more erect or nodding flowers borne at the stem apex

  • Details T. grandiflorum is a vigorous perennial forming a large clump of erect stems each carrying a whorl of three broadly ovate leaves and a solitary terminal flower to 10cm across, with three recurved white petals

  • Plant range E North America

Characteristics

  • Foliage Deciduous

  • Habit Columnar/Upright

  • Toxicity

  • 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

Sunlight

  • Partial Shade

  • Full Shade

  • Aspect North-facing or East-facing or West-facing

  • Exposure Sheltered

Soil

  • Sand

    Sand

  • Loam

    Loam

  • Chalk

    Chalk

  • MoistureMoist but well-drained

  • SoilSand, Loam, Chalk

  • pHAcid, Neutral

Size

  • Ultimate height 0.1-0.5 metres

  • Ultimate spread 0.1-0.5 metres

  • Time to ultimate height 2-5 years

How to grow

Cultivation Grow in deep, moist but well-drained, humus-rich, preferably acid to neutral soil in deep or partial shade. Mulch in autumn with leaf mould

Propagation Propagate by seed in pots in a shady cold frame as soon as seed is ripe; takes 5-7 years to reach flowering size. Propagate rhizomes by division after flowering or cut out the growing point from the rhizome after flowering, which stimulates the formation of offsets

Suggested planting locations and garden types Flower borders and beds Underplanting of Roses and Shrubs

How to care

Pruning No pruning required

Pests Slugs and snails may be a problem

Diseases Generally disease free

Advertise here

Did you find the information you were looking for?

RHS members can get exclusive individual advice from the RHS Gardening Advice team.

Join the RHS now

Get involved

We're a UK charity established to share the best in gardening. We want to enrich everyone's life through plants, and make the UK a greener and more beautiful place.