Outsidepride Showy Evening Primrose Wildflower Seed - 1/8 LB Showy evening primrose wildflower seeds are grown in USDA Zones 6 - 10. These perennial flower seeds will reach a height of 12 - 16 inches. Oenothera speciosa is a favorite of many gardeners. It has soft pink, silky flowers with yellow centers that are 2  inches across. It is a vigorous plant that spreads by rhizomes and can establish large colonies if given room in a naturalized setting. Sow 2 - 3 seeds per plant or sow this wild flower seed at 1 lb per acre