The common evening primrose is Oenothera biennis which bears pale yellow, fragranton a 3 to 4 ft. plant, opening only in the evening. It is almost a weed in some soils, self-sown being all too frequent. It is best treated as a , being sown in June. 0. tetragona has rather better habits, and is a useful perennial for the herbaceous border. It bears lemon-yellow (which open during the daytime), balanced by firm, slighdy glaucous , 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 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.