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
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.
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
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.
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.