Flower spike of Oenothera lindheimeri

The flower spikes of Oenothera lindheimeri form as long, flexible shoots bearing terminal raceme-like inflorescences. A characteristic feature of their development is sequential flowering, where buds, open flowers, and seed capsules are present simultaneously on a single shoot. The length of the flowering portion varies from 10 to 80 cm, with the total height of the plant, including the flower spikes, reaching 50–150 cm.

The agronomic value of the flower spikes is determined by their rigidity and susceptibility to lodging, which increases with excess nitrogen or light deficiency. To maintain ornamental quality and stimulate repeat flowering, spent shoots should be pruned. The slender structure of the flower spikes limits their suitability for cut flowers, while leaving the shoots through the winter promotes active self-seeding of the crop.