Ceratophyllum demersum

RHS Plant Profile
hornwort
hornwort visionspictures.com

Other common names

cedar moss, coon tail, cyrnddail, fish blankets, horn weed, morass weed, rigid hornwort

Aquatic

A submerged, aquatic, mat-forming perennial, growing to a depth of around 150cm, with feathery, dark green leaves and a bushy habit. Small, inconspicuous pale green flowers appear on the leaf axils between May and July. It thrives in both still or slow-moving water and works as a great oxygenator, providing a steady supply of oxygen and acting as a filter to keep ponds clear and healthy

Position

Full shade, Full sun, Partial shade

Soil Types

Clay, Loam

Max Height

Up to 10 cm

Max Spread

1-1.5 metres

Size

Time to Maturity
5–10 years
Max Spread
1-1.5 metres
Max Height
Up to 10 cm

Growing Conditions

Clay Loam
Moisture
Poorly–drained
pH
Acid or Alkaline or Neutral

Position

Full shade Full sun Partial shade
Aspect
West–facing or South–facing or North–facing or East–facing
Exposure
Exposed or Sheltered
Hardiness
H4

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Ceratophyllaceae
Native to GB/Ireland
Yes
Foliage
Deciduous
Habit
Submerged
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
Name Status
Correct
Plant Range
EC Europe to Africa

How to Grow

Cultivation

Grow in water up to 150cm 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. See pond plants for further advice

Propagation

Propagate by stem cuttings and allow to float in water

Pruning

No pruning required

Pests

Generally pest-free

Diseases

Generally disease-free