• 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

Ceratophyllum demersum

hornwort

  • Other common names hornwort
    cedar moss

    coon tail
    fish blankets
    horn weed
    morass weed
    rigid hornwort

    see more
  • Family Ceratophyllaceae

  • Genus Ceratophyllum are submerged aquatic perennials with whorled, linear leaves more crowded near the stem apex, and tiny insignificant flowers in the leaf axils in summer

  • Details C. demersum is a submerged perennial with forked, dark green leaves, with tiny flowers in summer

  • Plant range EC Eur. to Afr.

Characteristics

  • Foliage Deciduous

  • Habit Submerged

  • 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)

    H4

Colour

Sunlight

  • Full Sun

  • Partial Shade

  • Full Shade

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

  • Exposure Sheltered or Exposed

Soil

  • Clay

    Clay

  • Loam

    Loam

  • MoisturePoorly-drained

  • SoilClay, Loam

  • pHNeutral, Acid, Alkaline

Size

  • Ultimate height Up to 10 cm

  • Ultimate spread 1-1.5 metres

  • Time to ultimate height 5-10 years

How to grow

Cultivation Grow in water 30-90cm deep in full sun to shade. Plants float freely. Plants die back in winter but modified stem buds, turions, overwinter in bottom mud and re-grow in spring

Propagation Propagate by stem cuttings and allow to float in water

Suggested planting locations and garden types Low Maintenance

How to care

Pruning No pruning required

Pests Generally pest free

Diseases Generally disease free

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