Water-milfoils & Mare's-tails
What are they?
Mostly submerged aquatic plants of permanent water bodies, but also occasionally found on wet mud. Most species have feathery foliage, usually arranged in whorls of three to six along the stem, with the tiny flowers appearing in the axils of the leaves. Mare's-tail is not related to the water-milfoils but looks somewhat like them and grows in similar habitats.
Where are they found?
Native species are submerged aquatic plants of good-quality wetlands, found in ponds, lakes, dykes and similar water bodies. Parrot's-feather is similarly a plant of ponds and ditches, but may also be found on wet mud in seasonally dry ponds and will survive in less pristine conditions.
Identification
The number of leaflets in a whorl and the colour and arrangement of the flowers help to separate the species. Water-milfoil flowers have four sepals and four sepals, but these are so minute as to be easily considered absent. Mare's-tail flowers are variously male, female or bisexual, with similarly minuscule petals and sepals; when present, there is just a single stamen. Mare's-tail further differs in being a more rigid plant with stiff stems carrying simple - not pinnate - leaves, standing proud of the water surface or wet mud.
Parrot's-feather Myriophyllum aquaticum
Introduced from South America as an ornamental water plant but proving to be highly invasive. Sadly, often dumped in ponds and other waterways and potentially a serious threat to native wetland plant communities. Flowers May to August, tiny, white, in the leaf axils. Differs from native water-milfoils most obviously by its emergent shoots, clothed in waxy, finely-cut leaves.
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Whorled Water-milfoil Myriophyllum verticillatum
Native in wetlands throughout the region but generally uncommon to rare away from the lower reaches of the Broadland rivers, where it can be locally common. Flowers July to August, tiny, mostly in whorls of five in terminal spikes, held above the water surface. Leaves rather stiff compared with our other water-milfoils. From late summer, plants form short, club-shaped bundles of leafy stems, known as turions. These will become the over-wintering structures when the rest of the plant dies back and, in our area are diagnostic among water-milfoils.
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Spiked Water-milfoil Myriophyllum spicatum
Native in deeper water bodies throughout the region and by far our commonest water-milfoil. Flowers July to August, tiny, mostly in whorls of four in terminal spikes, held above the water surface. Leaves in whorls of four to six (mostly five), feathery and cut almost to the veins.
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Mare's-tail Hippuris vulgaris
Native in wetlands and formerly much more common and widespread but now local due to loss of habitat; can form large stands where it occurs. Flowers June to August, tiny, in the leaf axils with plants often bearing a mix of male, female and bisexual flowers. A very distinctive plant and unlikely to be confused with any other species, though superficially a little like the horse-tails. Differs from the water-milfoils in its simple leaves.
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