|Species:||Ranunculus aquatilis L., white water-buttercup, water crowfoot|
White water-buttercup, unlike its terrestrial cousins, is found in ponds, lake margins, ditches and streams. The small white flowers with yellow centers rise above the water surface. Many white water-buttercup plants have two distinct types of leaves: very finely divided, thread-like, fan-shaped underwater leaves, and floating or emersed leaves that appear scalloped. Often only the underwater leaves are present. The plants sometimes form conspicuous mats on the water surface
Leaf: The leaf form is variable depending on the season and growing conditions, but the leaves are always alternately arranged on the stem. Submersed leaves are branched into more than 20 thread-like segments. These fan-shaped leaves are 1-4 cm wide and are attached to the stem by 1-2 cm long leaf stalks. These underwater leaves generally collapse when removed from the water. When growing on mud, more compact versions of the submersed leaf will form. Floating leaves: are often absent. When present, these scalloped leaves (0.5-2 cm long) are flat and have 3 to 5 main lobes.
Stem: The long smooth or slightly hairy stem can grow to 1 m and is weak, branched, and rooting at the lower nodes.
Flower: Single flowers on stalks (1-6 cm long) rise above the water surface. Each flower is 1-2 cm across, has a yellow center, and 5 white petals. As the fruit matures, the petals detach and the flower stalks tend to curve away from the stem.
Fruit: White water-buttercup has clusters of 10 to 50 achenes per flower. Each achene is 1.5 -2.5 mm long, has a pointed end, and often has cross ridges.
Root: Fibrous roots often emerge from nodes on the lower portions of the stems.
Propagation: Seeds and stem fragments.
Importance of plant: Fruits are eaten by waterfowl. Some buttercup species are poisonous and others are used for medicinal purposes.
Distribution: Varieties are found nearly world-wide. Common throughout Washington.
Habitat: Ponds, lake margins, rivers, slow-moving streams or ditches.
May be confused with: Long-beaked buttercup (R. longirostris) and stiff-leaved buttercup (R. subrigidus) are similar and have recently been classified as varieties of white water-buttercup. Fanwort (Cabomba caroliniana) has leaves with an opposite arrangement. Water marigold (Megalodonta beckii) has opposite leaves on short stalks, that appear whorled and has yellow, sunflower-like flowers.
Line Drawings: Ranunculus aquatilis var. longirostris
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