''Decodon verticillatus'', the sole species in the genus ''Decodon'', is a flowering plant in the family

Lythraceae Lythraceae is a family of flowering plants, including 32 genera, with about 620 species of herbs, shrubs, and trees. The larger genera include '' Cuphea'' (275 spp.), '' Lagerstroemia'' (56), '' Nesaea'' (50), '' Rotala'' (45), and '' Lythru ...

. It is commonly known as waterwillow or swamp loosestrife. It is native to

wetland A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (anoxic) processes prevailing, especially in the soils. The ...

s in the eastern half of the United States and Canada.

Description

Waterwillow is a clump-forming shrubby

perennial A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also wide ...

that grows in swamps or shallow water. The stems are arching, angular, smooth and woody near the base, and up to tall. They sometimes root at the tip when they bough over and touch the mud. The leaves are

lanceolate The following is a list of terms which are used to describe leaf morphology in the description and taxonomy of plants. Leaves may be simple (a single leaf blade or lamina) or compound (with several leaflets). The edge of the leaf may be regula ...

, either in opposite pairs or in whorls of three or four. They are up to long and wide, smooth above and hairy beneath, on very short stalks. The rose-pink flowers grow in axillary clusters. The

calyx Calyx or calyce (plural "calyces"), from the Latin ''calix'' which itself comes from the Ancient Greek ''κάλυξ'' (''kálux'') meaning "husk" or "pod", may refer to: Biology * Calyx (anatomy), collective name for several cup-like structures ...

is cup shaped, the

corolla Corolla may refer to: *Corolla (botany), the petals of a flower, considered as a unit *Toyota Corolla, an automobile model name * Corolla (headgear), an ancient headdress in the form of a circlet or crown * ''Corolla'' (gastropod), a genus of moll ...

under wide with usually five petals narrowing at the base. The ten stamens are projecting with five longer than the rest. There is one pistil, one style and a superior ovary. The fruit is a spherical dark brown capsule with numerous reddish seeds. Flowering takes place in June and July.

Habitat

Waterwillow is found in swampland, in ditches, besides streams and in shallow water at the edges of ponds and lakes. It often forms thickets and occurs in the United States from Maine to Florida and west to Minnesota, Tennessee and Louisiana, as well as in eastern Canada.

Fossil record

Seeds of ''Decodon'' from the late

Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campani ...

(73.5 MA) of northern

Mexico Mexico ( Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guate ...

is the earliest fossil record of the genus. Seeds of the genus are known in

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located enti ...

from

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Pleistocene The Pleistocene ( , often referred to as the '' Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed ...

. These seeds are assigned to an extinct species, ''D. globosus''. A seed very similar to the modern American species has been found in sediments from Ipswichian in

Ireland Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic Ocean, in Northwestern Europe, north-western Europe. It is separated from Great Britain to its east by the North Channel (Grea ...

, and it is possible that the plant survived until the

last interglacial The Last Interglacial, also known as the Eemian (primarily used in a European context) among other names (including the Sangamonian, Ipswichian, Mikulino, Kaydaky, Valdivia and Riss-Würm) was the interglacial period which began about 130,000 ye ...

in western Europe.

Associated species

* The larva of the hydrangea sphinx, ''

Darapsa versicolor ''Darapsa versicolor'', the hydrangea sphinx, is a moth species of the family Sphingidae that inhabits eastern North America, often in wetlands. It was first described by Thaddeus William Harris in 1839. Its wingspan can reach 58 to 80 mm, ...

'', feeds on waterwillow. * The larva of the waterwillow stem borer moth, '' Papaipema sulphurata'', feeds on waterwillow.Endangered Species/Biodiversity Conservation
Lloyd Center for the Environment

References

{{Taxonbar, from=Q2123494 Lythraceae Flora of North America Plants described in 1753 Taxa named by Carl Linnaeus