The common evening primrose is Oenothera biennis which bears pale yellow, fragrant flowers on a 3 to 4 ft. plant, opening only in the evening. It is almost a weed in some soils, self-sown seedlings being all too frequent. It is best treated as a biennial, seed being sown in June. 0. tetragona has rather better habits, and is a useful perennial for the herbaceous border. It bears lemon-yellow flowers (which open during the daytime), balanced by firm, slighdy glaucous leaves, all summer. Height about 2(]2 ft. This species prefers a cool soil. 0. missouriensis (macrocarpa) reaches 9 in. and is of trailing habit with bright red stems and large yellow flowers from June to October. They usually only open in the evening. Both these species can be increased by seed sown in a cold frame in May or June.

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