Oenothera glazioviana Micheli

Global description
Oenothera glazioviana is a biennial to shortly perennial plant, erect, with rosette of basal leaves, reaching 1.50 m high. The simple and alternate leaves, stalked on the rosette, sessile on the stem, are elongated elliptical, narrowed on the two ends, hardly serrated. The large flowers with 4 petals are a beautiful lemon yellow in colour. The fruit is a tetragonal cylindrical capsule containing numerous angular brown to dark brown seeds.
 
Growth habit
Upright grass with rosette of basal leaves, biennial to shortly perennial, reaching 1.50 meters high.
 
Underground System
Taproot
 
Stem
The stem, in general branched along its length, measure 30 cm to 1.50 m high. It is marked with red dots. Its surface is covered with a more or less dense pubescence of short erect hairs covered with long erect hairs, with tuberculate red base.
 
Leaf
The leaves, simple and alternate, stalked at the rosette, become sessile to short-stalked along the stem. The leaf blade is narrowly elliptic to lanceolate or oblanceolate, with base narrowly attenuate, with sharp, pointed end to slightly obtuse, weakly serrated margin. Its surface is often wavy, veined very visible, covered with pubescence ranging from silky to stiff hairs. The rosette leaves measure 13 to 30 cm long and 2 to 5 cm wide, those of the stem 5 to 15 cm long and 2.5 to 4 cm wide.
 
Inflorescence
The inflorescence is a dense terminal cluster.
 
Flower
The flower is large (8 to 10 cm in diameter; floral tube of 3 to 5 cm long), a lemon yellow or light yellow in color. The 4 sepals (2.8 to 4.5 cm), are erect to spreading, yellowish green to red in colour. The 4 obovate petals (3.5 to 5 cm) with a rounded end and a triangular base, are yellow in colour. While wilting, they become reddish orange. The anthers of the stamens are large, 1 to 1.2 cm. The stamens consist of a filament of 5 to 15 mm long and a yellow anther of 7 to 10 mm long. The ovary is more or less densely pubescent, with long red hairs with tuberculate base. It has a long style (2-6 cm) that exceeds the stamens.
 
Fruit
The fruit is a cylindrical capsule with 4 angles, 25 to 40 mm long and 4 to 6 mm wide, thinner at the end, pubescent. It contains many seeds.
 
Seed
The seed (1 to 1.4 mm long and 0.8 to 1 mm wide), angular, riddled with holes, is brown to dark brown in colour.

Origin

Species native to North America.
 
World distribution
Commonly cultivated and naturalized in the world.