The botanical name for primrose is Primula, from the Latin word for "early," and the name suits the blooming season of this cheerful spring beauty. Primroses flower in late winter or early spring, thriving in cooler temperatures that dismay many summer-loving perennials. Although most primroses share this early bloom time, the primrose family has a variety of members and the tough evening primrose (Oenothera spp.) isn't a member of the Primula family at all.
The primrose family has more than 600 species, but many modern gardens sport only the hybrid polyantha primrose (P. x polyantha). These primroses grow 6 to 12 inches tall with crinkled, elongated oval leaves and may bloom for nearly a month in early spring. Named hybrid strains include "Pacific Giant," with generous flowers in many available colours, and "Cowichan" primroses that lack the yellow eye and have red-tinted leaves. Miniature polyantha primroses have small flowers on short stalks, and "Gold Laced" hybrids show off gold-edged leaves. None of the hybrids tolerate heat or dry conditions.
While they don't carry the loveliest moniker, drumstick primroses (P. denticulata) do have distinctly drumstick-shaped flower stalks. The flowers appear at nearly the same moment as the scoop-shaped leaves and cluster in lilac, pink, blue or white balls on a wide stem. The flower stalks grow up to 12 inches tall. Like most primroses, drumstick primroses prefer cool climates and bloom before many other perennials emerge from the ground. They grow relatively quickly from seed but often die out in hotter gardens.
Although it blooms slightly later than the drumstick primrose, the Japanese primrose (P. japonica) looks like the drumstick primrose's big brother. Not satisfied with just one cluster of flowers, this primrose produces whorls of flowers spaced along tall, 24-inch flower spikes. The most common flower colour is a rich purple with a yellow eye, but nurseries produced white, pink and red varieties. Japanese primrose blooms in mid to late spring and prefers shady, moist locations.
Evening primroses (Oenothera spp.) are as different from the Primula family as night from day. These primroses have narrow, smooth leaves and wide, poppy-shaped flowers that appear in late spring to early summer. Evening primroses thrive in sunny sites and dry, average soils. They spread rapidly through underground stems. Although this habit makes them ideal for a tough-as-nails ground cover, it also means they may invade your neighbour's yard. "Sundrops" (O. macrocarpa) are not as invasive or showy as "Mexican" evening primroses (O. speciosa) and have yellow flowers. Mexican evening primrose has white or pink flowers.