By Joshua Harris
SPECIES DESCRIPTION
The water violet is an aquatic plant which grows mostly submerged beneath the water surface, although the stem and leaves can sometimes float horizontally on the water surface. The leaves are a pale lime green colour and are limp if they are taken out of the water. The leaves are pinnatisect, meaning that they are divided into thin segments, similar to the leaves of ferns. The plant is deciduous but perennial, with the leaves dying off in the winter and growing back the next year. They need good sunlight in order to grow, and can live in any type of soil – sandy, loamy, or clay.
Only the flower spike emerges above the water surface and this can reach up to 80cm, although they can be much shorter. It takes 5-10 years to reach its tallest height, and can spread horizontally a distance of 0.5 – 1 metre. The flowers are present between May to June and appear very similar to a primrose – white or pale pink with a yellow centre and 5 petals. In fact, the water violet is not related to other Violets but is rather a species of Water Primrose. The water violet is a hermaphrodite, with both male and female organs. It has pin-eyed and thrum-eyed flowers, like Primrose, and requires cross pollination between pins and thrums to set seed. The flowers are pollinated by insects such as bees and butterflies. It also spreads through vegetative growth, forming colonies which do not set seed. The plant can grow fast.
WHERE CAN I FIND WATER VIOLETS?
It was formerly widespread across the east of England and the midlands, however it is now mainly confined to the Fens, the Somerset Levels, parts of Kent, and a handful of other sites. It is the county flower of Huntingdonshire. There are a handful of records in Scotland and Wales, and it has been introduced at some sites in Ireland. Globally, it is distributed across Europe as far east as the Ural mountains, with the exception of Spain and Portugal, the southern half of Italy, the northern parts of Scandinavia, and south-east Europe.
Because it is highly sensitive to pollution, the presence of the water violet is an indicator of a water source being clean and not polluted. The water violet is often grown in ornamental ponds.
CAUSE OF DECLINE
As an aquatic plant, the water violet is very vulnerable to water pollution, eutrophication and algal blooms. In addition, it is also threatened by drainage and prolonged drought, vegetation clearance, boat traffic, increasing salinity (due to evaporation of water at higher temperatures), and trampling by cattle. It is able to survive temporary summer drought, but not permanent drainage. It is declining and is listed as Vulnerable on the Red Data List for England. Many colonies were lost before 1930 in England.
ROLE IN THE ECOSYSTEM
The water violet is found in still or slow moving, shallow aquatic environments: ponds, ditches, and the slow flowing backwaters of some rivers. Its bushy leaves can create dense shelter for aquatic animals such as dragonfly nymphs, water beetles, tadpoles, snails, and fish and their larvae. The flowers provide nectar for bees and butterflies. The plant also oxygenates the water.
We’re calling on government to act now for our freshwater ecosystems, for nature and for our future. Head to our Not so Freshwater campaign page to learn more.
Bibliography
https://plantatlas.brc.ac.uk/plant/hottonia-palustris (includes map of UK distribution)
https://www.gbif.org/species/4006551 (map of global distribution)
https://www.rhs.org.uk/plants/25646/hottonia-palustris/details
https://www.plantlife.org.uk/uk/discover-wild-plants-nature/plant-fungi-species/water-violet
