Flora of the River
Daphne Levinge
The Shannon provides many different
habitats for a wide variety of species
of flora including some rare and very
interesting plants.
To the visitor stepping ashore along the
river bank or at the lake edge, the shore
can be wet and soggy or sometimes rocky
and wave-swept. For most of the plants
which inhabit these shores, the amount of
water present is the determining factor as
to whether they can establish themselves
and survive successfully. Many of these
plants have adaptations which enable them
to cope with the water environment: some
plants, like the microscopic algae, live rootless in. the water; water lilies and
pondweeds have large floating leaves;
other plants live submerged in shallow
water like the Canadian pondweed and
water milfoils. Some plants prefer the
sheltered waters of calm bays to the fast-flowing river sections.
Moving inland from the water’s edge,
other factors become important for the
plant. Is the soil lime-rich or acidic? Is it
shallow or deep to allow short grassland
vegetation or rich woodland to develop?
Varied Habitats
Thus different Shannon habitats are
found with a characteristic group of plants
tolerant of or preferring the particular conditions of water, soil or climate. Of course,
some plants are so tolerant of these conditions
that they are found not only through-out the
Shannon system but all over
Ireland. These common species, because
they are widespread and familiar, are not
referred to in the list which can be found in
the appendix.
Rare Plants
Some rare Irish plants can be found
within the Shannon system. The origins of
their presence here, and indeed in Ireland,
is open to speculation. Some grasses and
sedges and the juniper may have survived
the Ice Age on high ground and later grad-
ually colonised the lowlands. As the climate
warmed up after the Ice Age, plants
migrated into Ireland from all directions.
Some of the orchids appear to have originated in the Mediterranean area;
from continental Europe came Irish fleabane which
is only found in Britain and Ireland at the
edge of Lough Derg. The blue-eyed grass,
which is also very rare, is a plant associated
with the North American flora and this too
may be found at the edge of Lough Derg.
Other rare plants which can be found may
have been introduced with man’s help,
such as the insect-eating North American
pitcher plant. Many of these rare plants
survive because they colonise conditions
which they like and because they are under
less competitive pressure than in Britain
and Europe, with their richer flora.
Shannon Species
Exploring the Shannon flora is rewarding: the flora is rich and many of the rarer
Irish species are easily found. Most species,
except possibly the grasses and sedges, are
easily identified from an illustrated flora
(see bibliography). The list which can be
found in the appendix includes most
species characteristic of the Shannon,
arranged by the habitats in which they are
most likely to occur. The most striking
Shannon habitats include the deep and
shallow waters of the river and lakes, the
reedbeds which develop from deposits of
sediment in lakes and slow flowing river
sections. Behind thereedbeds, fens are
found where sedges, grasses and characteristic flowering plants, with willow trees,
are dominant. Worth exploring too are the
shores of Lough Ree and Lough Derg: characteristic plants of their rocky shores are
described in the appendix.
