Ceratophyllum demersum
Hornwort
Common names: Rigid hornwort, Coontail
At a glance
- Light
- Partial shade
- Pot size
- from 30 l
- Lifespan
- Perennial
- Hardiness
- Hardy
- Origin
- Native to Germany
Photo: Javier martin · Public Domain · Source
Description
Hornwort (Ceratophyllum demersum) is a rootless aquatic plant that floats freely in water with its fine, feathery leaves, drifting loosely among other plants. It is one of the most important oxygen producers in garden ponds and a strong competitor against algae, as it competes for nutrients and light. The tiny, inconspicuous flowers appear underwater and play little role in the pond; the plant is valued solely for its function as a water plant. In winter it collapses into buds on the pond bottom and survives the cold season there.
Care instructions
Plant hornwort loosely in the water; it does not root and drifts freely among other plants. It prefers depths of 30 to 100 cm in a bright to semi‑shaded spot in the pond. Trim dense shoots in summer to allow enough light to reach the pond bottom. In autumn the plant will naturally sink and overwinter on the bottom, so it does not need to be removed. In spring remove only the browned parts; the rest will reliably regrow.
The care notes were machine-translated from German.
Soil & site
Soil pH
Soil type
moist, nutrient-rich, loamy, clayey
Hornwort does not root in the classical sense, but floats freely in the water and absorbs nutrients directly through the surface of its shoots. What matters, therefore, is nutrient-rich, slightly alkaline to neutral water rather than soil in the usual sense. A fine, loamy to clayey substrate on the pond bottom supports the few rhizoids that serve as anchors. In very soft, nutrient-poor water, the plant grows much more weakly.
Feeding
Medium feeder
As an underwater plant, hornwort needs no classical fertilising, but lives on the nutrients dissolved in the pond water. Too many nutrients in the water, for example from fish stocking or fallen leaves, promote unwanted algae rather than the hornwort itself. A balanced pond ecosystem with compost on the bank and little additional nutrient input is entirely sufficient. Do not add any kind of fertiliser directly to the water.
Overwintering
Hornwort usually survives the winter as a whole plant on the pond bottom, where it goes dormant in frost. In shallow ponds that can freeze to the bottom, the plant forms dense winter buds (turions) in autumn, which sink and sprout again in spring. A pond depth of at least 80 cm in the winter zone protects the stands reliably. Additional protection is not necessary in most gardens in Germany, Austria and Switzerland.
Propagation
Methods
- Cuttings
- Division
The easiest way to propagate hornwort is by cuttings: a broken-off piece of shoot grows new shoots and rhizoids by itself in the water. Simply place the shoot tips in the pond water, either floating freely or lightly anchored; it takes no more effort than that. Larger stands can also be propagated by dividing dense bunches of shoots, which you then spread in other spots in the pond. In spring, freshly placed shoots grow into new, dense cushions of plants within a few weeks.
For your garden
Grow Hornwort yourself
Gartenkern tells you when frost is coming, when to sow and when to harvest, for your location.
Free, no time limit
Notes from real gardens
What other gardeners have written down about this variety, anonymous and voluntary.
No notes shared yet. Will you be the first to write one down?