The diverse iris genus contains more than 200 distinct species and countless cultivars. Iris is the goddess of the rainbow, and you can find iris blooms in pink, blue, lilac, purple to brown, yellow, orange, almost black, and white. There are no true reds. Many types of iris have fine foliage, whether short or tall, which is a good thing, because the flowers have only a brief period of bloom. These perennials return reliably year after year. Irises usually have basal leaves in two ranks -- linear to sword-shaped -- often resembling a fan, arising from a thick rootstock (or rhizome), from fibrous roots, or, in some species, from a flower bulb.
How to grow: Most irises need full sun. Except for those like the water flag (Iris pseudacorus), which delights in a watery spot, or the Japanese iris (I. ensata), which thrives in humus-rich moist soil, most irises also prefer a good well-drained garden soil. If plants are protected from iris borers, they become permanently established in the garden.
Propagation: By division after flowering or in the fall or from seed.
Uses: Even though the bloom period is short, a bed of irises is ideal for a flower garden. There are also irises for the poolside and the pool, the wild or woodland garden, the early spring bulb bed, the cutting garden, and the rock garden.
Related species: Iris germanica (tall bearded iris), hardy from Zones 4-8, usually comes to mind when people think of irises. The flowers come in a multitude of color combinations and sizes, with hundreds of new varieties introduced every year. This iris is usually spring blooming, but some rebloom in fall. I. cristata (crested iris), hardy in Zones 5-8, prefers partial shade and a humus-rich soil and blooms in early spring. It is lavender-blue with a two-inch yellow crest across a six-inch stem. I. ensata (Japanese iris) is hardy in Zones 6-8. Richly colored blossoms are often more than six inches wide on stiff, tall stems, blooming in June. The blue flag, I. versicolor, is a lovely three-foot wildflower from the Northeast that appears in ditches and boggy areas along country roads. It is a great pond plant. I.I. sibirica (Siberian iris), hardy in Zones 4-8, has large flat lovely 3- to 4-inch flowers on 30-inch stems and great foliage-the swordlike leaves stand erect and eventually form a large clump. I. pseudacorus (yellow flag) is also a beautiful plant for a bog or at the edge of a pond or pool. The flowers, blooming from May to June, are yellow on 40-inch stems. It is beautiful but can be invasive.
Scientific name: Iris species