Common Evening Primrose

Plant. Usually seen as single stems up to six feet tall with some branching near the top. This plant was approximately six feet tall but with many branches so that it looked like a small shrub.
Flowers open at twilight and may close early in the morning; these flowers were still open at 8:30 a.m.
Flowers are yellow, have 4 petals with notched tips, 4 sepals, and 8 stamen.
Sepals are strongly reflexed against the stem.
Leaves. Simple, alternative. Leaves lanceolate to oblong, spiraling, ascending or spreading around stem