• 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

Tiarella wherryi

Wherry's foam flower

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
© Christopher Whitehouse
  • Other common names Wherry's foam flower

  • Synonyms Tiarella collina
    Tiarella cordifolia var. collina

  • Family Saxifragaceae

  • Genus Tiarella are rhizomatous herbaceous perennials forming a clump of rounded, more or less palmately lobed leaves, with very small, star-shaped flowers in terminal panicles or racemes on erect stems

  • Details T. wherryi is a compact herbaceous perennial to 25cm in height, forming a clump of deeply 3-lobed, purple-tinted leaves with narrow, erect racemes of small, white or pinkish flowers from late spring

  • Plant range SE North America

Characteristics

  • Foliage Deciduous

  • Habit Clump-forming

  • 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

  • Full Sun

  • Partial Shade

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

  • Exposure Sheltered

Soil

  • Chalk

    Chalk

  • Loam

    Loam

  • Clay

    Clay

  • MoistureMoist but well-drained, Poorly-drained

  • SoilChalk, Loam, Clay

  • pHAcid, Alkaline, 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 Ideally grow in cool, moist, humus-rich soil in partial or full shade but can tolerate a wide range of soils and can spread freely. Protect from excessive winter wet

Propagation Propagate by seed in pots in a cold frame as soon as seed is ripe or in spring. Propagate by division in spring

Suggested planting locations and garden types Flower borders and beds Ground Cover Underplanting of Roses and Shrubs Cottage & Informal Garden Rock Garden

How to care

Pests Slugs may be a problem

Diseases Generally disease free

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.