Rivers and streams – plant life

While slow flowing water can have rich populations of freshwater plants, some can also grow in fast-running rivers and streams.

In the shade

If plants have reasonably stable surfaces to take root, they can survive. Mosses and liverworts grow in great luxuriant carpets on boulders and rock faces, especially in shady habitats, where they are kept moist by spray. You can also find the rare Killarney fern in such places, as well as filmy ferns, which need constant high humidity.

In the light

Where there is more light, higher plants can form large weed-beds. Submerged plants such as starworts, milfoils, crowfoots and pondweeds form tapestries of green and brown in clear, unpolluted waters. In early summer, rivers such as the Teifi are briefly carpeted with the white flowers of water crowfoots.

Slower water

The rare floating water-plantain can be found in a few rivers in North Wales while floating-leaved plants such as water-lilies grow in slower-flowing water, their leaves safe from damage by strong currents.

On the water’s edge

In wet ground close to the water’s edge many marsh plants, grow and rivers may be important for spreading these plants. Yellow flag-iris, for instance, has floating seeds that can be carried to new habitat by the current.

On the banks

Although various trees may grow along river banks, some are particularly important. Alder and willows are particularly common, and their dense roots help to stabilise riverbanks. Unfortunately, in recent years many alders have been killed by alder disease, a fungus related to Dutch elm disease.

Conservation

Weedbeds provide an important refuge for invertebrates and fish in the middle reaches of rivers, and rivers with this type of vegetation are now protected by the Habitats Directive.