Siberian irises and bearded irises bloom in the spring, usually from April to June, depending on the climate. Both grow in zones 3 to 9. They need sunny locations and tolerate dry conditions. Both have large ruffled flower petals, some that arch up, some down. Bearded irises have the larger flowers of the two varieties.
Siberian iris plants have blooms that are either blue, white or lavender. They have beautiful grass-like foliage and long, fibrous roots and grow best in well-drained soil. Once established, Siberian iris are drought tolerant and benefit from mulch. They form large clumps and are best left undisturbed for 5 to 6 years.
Bearded iris plants are named for a fuzzy ridge that is obvious along each of 3 downward-facing petals, called falls. The 3 upward facing petals, called standards, may be a different color than the falls. Blooms can be found in shades of blue, pink, purple, gold, apricot, burgundy, russet, white, yellow and bi-color. These iris plants have thick, sword-like leaves and fleshy underground stems called rhizomes. Feeder roots extend into the soil from the rhizome, which grows at soil level or just below the soil. Remove any mulch or soil covering the top of the rhizome so it is exposed to the sun. Each year the rhizomes grow longer and plants can become crowded. Clumps should be divided every 3 to 5 years for best results.