Iris Classification – Bearded Irises

The following is derived from information on The American Iris Society (AIS) website at The AIS divides irises most often used as garden plants into three main groups: Bearded Irises, Aril Irises and Beardless Irises.

Bearded Irises are identified by thick, bushy “beards” on each of the falls (lower petals) of the blossoms. Originally, most of these were native to central and southern Europe. The American Iris Society has further divided bearded irises into six groups for judging awards.

1. Miniature Dwarf Bearded (MDB) are the smallest irises, with height up to 8 inches. They are also the earliest to bloom. They are most effective in rock gardens or planted in drifts where they make a “carpet of color.”

2. Standard Dwarf Bearded (SDB) irises range in height from 8 to 16 inches. They begin to bloom as the MDBs are ending, still quite early in the iris season. They are best displayed in clumps. Their colors are nearly unlimited.

3. Intermediate Bearded (IB) irises are 16 – 27 1/2 inches tall. Their bloom season overlaps the SDBs and the TBs. IBs are large enough that their individual stalks may branch, forming an elegant bouquet. They display a large amount of color and color patterns.

4. Border Bearded (BB) irises are essentially small versions of Tall Bearded irises. They are the same height as IBs and their bloom size is the same.

5. Miniature Tall Bearded (MTB) irises look more dainty and delicate. The blooms are even smaller than on the Border Bearded and their stems are thinner. MTBs are also from 16 to 27 1/2 inches in height. Miniature Tall Bearded irises are also called “table irises” as they often used in flower arrangements.

6. Tall Bearded (TB) irises are a minimum of 27 1/2 inches tall. Many TBs can reach heights of 40 inches or more. TBs branch and have numerous buds. Tall Bearded irises come in a wide variety of colors and patterns; some display ruffles or lacy edgings.