The plant is a rhizomatous, hairless, perennial aquatic plant. Its name is derived from Greek bous, meaning "cow", "ox" etc. and tome, a cut (the verb 'temnein' meaning "to cut"), which refers to the plant's swordlike leaves.
Other than suggested by its English common name, it is not a true rush. It is native to Eurasia and grows on the margins of still and slowly moving water down to a depth of about 3 m. It has pink flowers. Introduced into North America as an ornamental plant it has now become a serious invasive weed in the Great Lakes area. In Israel, one of its native countries, it is an endangered species due to the dwindling of its habitat. It can also be found in Great Britain locally, for example Butomus umbellatus at Gwent Levels SSSI on the Caldicot and Wentloog Levels
The plant has linear, pointed leaves up to 1 metre long, or more. The leaves are triangular in cross-section and arise in two rows along the rhizome/base. They are untoothed, parallel veined and twisted.
The inflorescence is umbel-like consisting of a single terminal flower surrounded by three cymes. The flowers are regular and bisexual, 2 to 3 cm across. There are three petal-like sepals which are pink with darker veins. They persist in the fruit. The three petals are like the sepals but somewhat larger. 6 - 9 stamens. Carpels superior, 6 - 9 and slightly united at the base. When ripe they are obovoid and crowned with a persistent style. Ovules are numerous and found scattered over the inner surface of the carpel wall, except on the midrib and edges. Fruit is a follicle. The seeds have no endosperm and a straight embryo. It flowers from July until August.
Butomaceae has been recognized by most taxonomists as a plant family; it is sometimes called the "flowering-rush family".
The APG II system, of 2003 (unchanged from the APG system, 1998), also recognizes such a family, and places it in the order Alismatales, in the clade monocots. The family counts a single species, Butomus umbellatus.
At the ranks of family and order this is the same placement as in the Cronquist system. However, Cronquist assumed a much smaller order and assigned the order to subclass Alismatidae, in class Liliopsida [=monocotyledons].
B. umbellatus is cultivated as an ornamental waterside plant.
In parts of Russia the rhizomes are used as food.
- Angiosperm Phylogeny Group (2009), An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG III, Botanical Journal of the Linnean Society 161 (2): 105–121, doi:10.1111/j.1095-8339.2009.00996.x, retrieved 2010-12-10
- Natural World Magazine, Spring 2009, The Wildlife Trust, published by Think publishing
- Rose, Francis (2006). The Wild Flower Key. Frederick Warne & Co. pp. 480–481. ISBN 978-0-7232-5175-0.
- "RHS Plant Selector - Butomus umbellatus". Retrieved 18 June 2013.
- USDA info
- University of Florida, Center for Aquatic and Invasive Plants
- Flora of Northern Ireland
- Tel Aviv Univ. close up of flower
- Global Invasive Species Database
- Butomaceae in L. Watson and M.J. Dallwitz (1992 onwards) The families of flowering plants: descriptions, illustrations, identification, information retrieval. Version: 27 April 2006. http://delta-intkey.com.
- Monocot families (USDA)
- Butomaceae in the Flora of North America
- NCBI Taxonomy Browser
- links at CSDL, Texas
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