The American Iris Society has divided bearded irises into six groups (horticulture classifications) for garden judging awards.
1. Tall Bearded Iris (TB)
These iris have stalks with a height of 27-1/2 inches (70 cm) and above, with branching and many buds. Each stalk makes a stately arrangement in the garden or in a vase. In addition to a wide variety of colors and patterns, TB iris display other qualities (such as ruffling and lacing) more frequently than do the other classes. (Example: TB Iris: Revere)
2. Border Bearded Iris (BB)
Are essentially small versions of TB iris in the same height range and bloom size as intermediates, but blooming with tall bearded iris. Good BB iris have round, ruffled petals complementing their small size. (Example: BB Iris: Bermuda Triangle)
3. Miniature Tall Bearded Iris (MTB)
This class is distinguished by daintiness and delicacy. An MTB iris clump looks like a cloud of butterflies. Height from 16 to 27-1/2 inches (41-70cm). The blooms are smaller than BB iris with thin, wiry stems, often called “Table Irises,” because they are so well suited for arrangements. (Example: MTB Iris: Holiday in Mexico)
4. Intermediate Bearded Iris (IB)
Standing from 16 to 27-1/2 inches (41-70cm) high, their bloom season overlaps SBD iris and TB iris. Although IB iris show their dwarf ancestry in early bloom season and very interesting color patterns, they are large enough so their individual stalks may be well branched, forming an elegant bouquet. Some varieties are nicest in clumps, where they present a large amount of color (like SDB iris), while others are showiest in specimen plantings, where the stalks and individual blooms may be seen to best advantage. (Example: IB Iris: Doe Z Doe)
5. Standard Dwarf Bearded Iris (SDB)
Some of the most useful garden plants, ranging in height from 8 to 16 inches (20 to 4cm), SDB iris begin blooming quite early in the iris season as MDB iris are ending. They are best displayed in clumps where they give the effect of a “cushion” of individual blooms. The colors are nearly unlimited since SDB iris show all the different “spot patterns” of miniature iris, as well as the plicatas and pinks seen in TB iris. (Example: SDB Iris Marksman)
6. Miniature Dwarf Bearded Iris (MDB)
The tiniest of bearded irises, are also the earliest to bloom. With heights of up to 8 inches (20cm), they are most effective in rock gardens or planted in drifts where they make a “carpet of color.” (Example: MDB Elf Esteem)
NOVELTY IRIS deviate from the mainstream in form, pattern, or other characteristics. For instance, the popular Space Age Iris have flounces, horns or spoons at the end of the beard. Read more in our blog post on Novelty Iris.
The definitions of iris groups and iris color patterns are adapted from American Iris Society publications.