A staple of cottage gardens and "old fashioned" perennial gardens, the bearded iris provides flowers that range in all colors except true red. Thousands of varieties (cultivars) exist today for gardeners to choose for time of flowering, flower color and other ornamental features. Bearded irises need a cool to cold winter dormancy and are not plants for subtropical or tropical regions. Although winter hardiness varies by species and cultivar, generally bearded irises are grown in U.S. Department of Agriculture (USDA) hardiness zones 3 through 8.
Overall there are about 300 different species of irises in the world, all native to the Northern Hemisphere in a wide array of habitats. Often the bearded iris that is commonly grown in gardens is called "German bearded iris" or botanically listed as Iris germanica. This is inaccurate as modern bearded irises are diverse in genetic lineage as well as in size and flower colors, and are best simply referred to as "bearded hybrids."
All bearded irises grow from rhizomes, which are horizontal stems that grow in the soil that store starches and produce both roots and upright fans of leaves. Typical garden-type bearded irises comprise any array of species and varieties, but are distinctly different than the bearded aril types. Aril irses are further broken down into groups named Onococyclus, Regelia and Regeliocyclus, and Arilbred, according to the American Horticultural Society's "A-Z Encyclopedia of Garden Plants." A main distinguishing feature of aril bearded irises from general bearded irises is that aril types go dormant in summer after their flowering.
From a scientific perspective, irises are divided into botanical subgenera and sections, according to "A-Z Encyclopedia of Garden Plants." The bearded hybrids are more readily classified for garden use and flower show exhibition based on characteristics like bloom season or height of the flower stem. The six categories are miniature dwarf, standard dwarf, intermediate, miniature tall, border, and tall.
Bearded iris flowers physically look different than those described as "beardless" or "crested." A bearded iris blossom comprises six petals: three are upright (or rarely horizontal) and are called "standards" and three are called "falls" and either curve, spread or droop down from the flower. On the curved shoulders of each fall petal (called a "haft") is a fuzzy cluster of stamens that resemble a beard. In the center of the bearded iris flower is a three-branched pistil (female sex organ). Often bearded irises emit a fragrance, ranging from light and sweet to spicy. Some bearded irises re-bloom in autumn and are called "remontant" to distinguish this feature from those that bloom only once in mid- to late spring.
Plant the rhizomes of bearded irises in late summer, although container-grown plants can be planted in spring before or during their flowering display. Choose a location that provides a fertile, neutral to slightly acidic soil. Also make sure the iris plants will receive at least six hours of direct sunlight during the growing season. Most will take all-day sunlight, but Erv Evans of North Carolina State University mentions that those that produce pale pink or pale blue petals look better if not grown in full sun. When growing, keep soil moist but do not place mulch atop the rhizomes as this can encourage rot as well as diminish flower production. In fact, plant rhizomes shallowly, so that the top surface of the rhizome is exposed to the air and light.