Water-lilies
What are they?
The true water-lilies are members of the family Nymphaeaceae, a mostly tropical family of plants that has a few members in temperate parts of the world. These are relatively primitive plants that are usually placed towards the beginning of the taxonomic tree. Their flowers are structurally very interesting, with the genus Nymphaea showing a gradient of change from petals to stamens towards the centre of the flower, while in Nuphar, the sepals are larger and more showy than the petals. These plants are highly adapted to a submerged aquatic life, rooting in wet mud and producing broadly rounded leaves that float at the water surface. Also included here are species from other plant families that are rather similar in their general appearance, but very different in their flowers and their much smaller leaves.
Where are they found?
These are plants of still or slow-moving waterways and are found in lakes, ponds, rivers, ditches, dykes and similar places.
Identification
The combination of leaf size and shape, coupled with flower colour and number of petals will make most of these plants straight forward to identify. Ornamental Water-lily comes in a wide range of forms and may sometimes be very difficult to tell from our native White Water-lily.
European White Water-lily Nymphaea alba
Native in a few areas in Fenland and the Broads, but also introduced widely eslewhere in lakes, ponds and old gravel pits. Flowers June to August. Flowers typically white, but occasionally pink-tinted, especially on the outer petals. Leaves all floating, rounded, 10-34cm across.
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Ornamental Water-lilies Nymphaea x marliacea and Nymphaea x laydekeri
Widely introduced in ornamental ponds, lakes, reservoirs and old gravel pits. Flowers June to September. A huge complex of hybrid water-lilies has been produced in the horticultural trade by crossing Nymphaea alba, N. odorata, N. tuberosa and N. mexicana to create varieties that are placed under N. x marliacea and by crossing N. alba, N. tetragona and probably N. mexicana under the name of N. x laydekeri.There appears to be no reliable source for identifying most of these with any great certainty and such a mix of crosses inevitably produces much variation. Plants may have white, yellow, pink or red flowers and the leaves may be all green, red beneath, or have variable amounts of purplish blotching which may be persistent or may fade with maturity of the leaf.
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European Yellow Water-lily Nuphar lutea
Native. Widespread and common in most open water habitats. Flowers June to August. Floating leaves 12-40cm across, elliptical in outline with petioles that are triangular in cross section and with rounded corners. Submerged leaves are also present which often have the appearance of large lettuce leaves. More tolerant of disturbance and nutrification of the water than the white water-lilies and more likely to be found in flowing water.
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Spatter-dock Nuphar advena
Introduced from North America as a garden ornamental and naturalised at a single site in Central Norfolk. Flowers May to June. Best told from European Yellow Water-lily by the leaves, many of which remain in a rather upright position rather than lying on the water surface and which have more or less rounded petioles.
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Fringed Water-lily Nymphoides peltata
Considered possibly native to a few areas in Fenland where it has been known for a long time, but more recently spreading as an introduction, especially in lakes, ponds and old gravel pits. Flowers June to September. Easily mistaken for a true water-lily, especially by its floating leaves, the fringed, five-petalled flowers are very different to those plants. The leaves can be told by their relatively delicate nature, 3-12cm across with slender, often sinuous petioles.
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Frogbit Hydrocharis morsus-ranae
Native. Once widespread in waterways but now rare except in parts of the Broads and Fens. Found in non-polluted ditches, dykes and small ponds. Flowers July to August. The white, three-petalled flowers are typical of the waterweed family (Hydrocharitaceae), but the plant otherwise looks like a very small water-lily, with leaves typically no more than 5cm across.
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Cape-pondweed Aponogeton distachyos
(Water-hawthorn) Introduced from South Africa as a garden ornamental. The sole member of a largely tropical group of plants, occasionally recorded from open waterways where it may have been deliberately planted, or as a survivor from discarded garden waste. The small, white flowers appear during the summer months and are carried in a highly distinctive, branched cluster, with each flower bearing just a single 'petal'.
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