Common evening primrose

'Common evening primrose' is a plant in the Oenothera genus with a scientific name of Oenothera biennis. The botanical name epithet for Common evening primrose (biennis) means 'biennial'.

http://www.fws.gov/longlake/flowers.htm
The flowers of the yellow evening-primrose are bright lemon yellow, 1 to 2 inches in diameter, with four reflexed sepals and four petals. Flowers are arranged in a spike-like fashion on stems which may grow up to 5 feet tall. All flowers do not bloom at once and they usually open in the evening. Flowers appear July-August

the fruit is a dry, coarse, slightly hairy, stalkless capsule about 2 inches long, with many small seeds. There may be over 50 oval fruits clustered along the upper 18 inches of the stem. These pods release their many seeds over a considerable period of time. It’s leaves are alternate, lance-shaped to oval, deep green, 1 to 5 inches long. Those on the lower stem have short stalks but they are stalkless on the upper stem.

The yellow evening-primrose is bushy and branched growing from a deep tap-root. There are several varieties of this species. It grows mainly on field edges and waste places. It grows in most of temperate North America and Canada.

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