The classification of iris is a vast subject. As the well-known horticulture professor Allan M. Armitage writes in his classic reference work:

"Due to the size of the genus, it continues to be stretched like the truth or squeezed like orange juice by taxonomists as more and more in-depth studies are conducted. For example, the further understanding of chromosomal differences has resulted in name or changes in relationships between taxa. Hybridization, both natural and formal, has also led to much head scratching about where to place the resultant progeny. . . . According to the various systems, the genus is divided into sub-genera  which again subdivide into sections, sub-sections, and groups or series. Each series may have 5-25 species and each species may be subdivided into numerous cultivars. Did you get that?" (Herbaceous Perennial Plants: A Treatise on their Identification, Culture, and Garden Attributes.third edition, page 571. Cited with permission of the author)

Fortunately for us, it is not necessary to understand taxonomy to love and grow irises. For our Minnesota gardens, the main classification differentiation we consider is between the bearded iris and the beardless, and their sub-groups, although a third bearded group, the Aril irises, now include some arilbred (hybrids between aril and bearded) irises that some growers are experimenting with in colder climates (with limited success, it should be added, although they grow well in Idaho, Eastern Washington state, and have overwintered as far north as Canada). Gardeners interested in more information about the Aril and Arilbred irises should refer to the Aril Society webpages. It is also possible to grow iris that rebloom, but they have different cultural requirements which are discussed on the various culture pages.


The bearded irises are further subdivided into six groups:

Miniature Dwarf Bearded (MDB)
Standard Dwarf Bearded (SDB)
Intermediate Bearded (IB)
Border Bearded (BB)
Miniature Tall Bearded (MTB)
Tall Bearded (TB)

All of these bearded iris groups can be successfully grown in Minnesota gardens, and, although the Tall Bearded iris are eye-catching, sometimes the slightly shorter Intermediate and Border Bearded cultivars, as well as the dwarfs, are easier to maintain in areas with high winds. The word "median" is used for all the bearded irises except the miniature dwarfs and the tall bearded. Some irises rebloom.


The beardless iris that is most common in Minnesota gardens is undoubtedly the Siberian; however there are several other groups of beardless iris that deserve to be more widely known and grown in Minnesota.  Of the six sub-groups listed by the AIS, five can be grown here in our state, including species irises native to our area. The sixth group, the Pacific Coast Natives (PCN) are intolerant of our climate. Irises from the following groups deserve a place in many Minnesota gardens:

Japanese Iris
Louisiana Iris
Siberian Iris
Spuria Iris
Iris Cristata


Abbreviations for different types of Irises:
Median Iris Heights

Iris Classifications


Abbr. Definition
Median All bearded iris classes (SDBs, IBs, BBs, and MTBs) between 8 and 27.5 inches.
MDB Miniature Dwarf Bearded, to 8" tall, the first bearded to bloom in earliest spring.
SDB Standard Dwarf Bearded, 8 - 16" tall, blooms in early spring.
IB Intermediate Bearded, 16 - 27.5" tall, generally blooms after SDBs and before TBs.
MTB Miniature Tall Bearded, 16 - 27.5" tall, the flower is no more than 6" combined width + height, generally blooms with the TBs.
BB Border Bearded, 16 - 27.5" tall, blooms with the TBs.
TB Tall Bearded, more than 27.5" tall, blooms in mid to late spring.
AR or (A) Aril iris; this name refers to oncocyclus and regelia species.
AB Arilbred, an iris hybrid that is part aril and part bearded iris.
AM Aril-med/Arilbred-med or Aril-median/Arilbred-median, shorter AR or AB irises that are crosses between Aril/Arilbred & dwarf or median irises, and that also meet the height requirements for classification as a median iris
RE varieties that produce more than one crop of bloom stalks in a single growing season.
HIS Historic Iris cultivars are any iris introduced over 30 years ago.


Parts of an Iris Flower


Part Definition
Standards (S) The upturned three petals, (technically called sepals) that surround the three style arms.
Falls (F) The downturned three petals, (correctly called petals) that possess beards. These may also be horizontally flared or flat instead of downturned).
Beards (B) Elongate groups of fuzzy hairs in the middle at the upper base of all three falls.
Space Age (SA) Iris have something extra, beard appendages called horns, spoons or flounces.
Spoons Appendages extending from the tip of the beards that widen into spoon shaped petaloids.
Horns A protrusion or extension of the beards, often ending in a point or may be hair covered.
Flounces Wide, folded, often canoe or fan shaped appendages extending from the tips of the beards.
Hafts Areas on each side of the narrow of the falls, on each side of the beards.
Shoulders The areas on the arching upper middle part of the falls on each side just beyond the haft areas.
Pistil The style arms with stigmatic lips and the ovary. The female flower parts.
Claw The narrow base of the standard and fall, the expanded leaf-like part is called the blade.
Ovary The enlarged green, three-chambered structure enclosing the ovules where fertilization occurs.
Spathes The pair of modified green leaves that enclose the flower bud, usually turning tan after it blooms.
Stamen The anther plus its attachment filament. The anthers contain the granular pollen. The male flower parts.
Rhizome Brownish, potato-looking, fleshy root.

Season of Bloom
VE = Very Early E = Early M = Midseason L = Late VL = Very Late

Descriptive Terms

Term Definition
Self Standards, style arms and falls are the same color, as a complete self they have the same color beards.
Amoena White standards and anthocyanin pigmented falls.
Reverse Amoena Anthocyanin pigmented standards and white falls.
Emma Cook pattern An amoena pattern with white standards and narrow anthocyanin pigmentation bordered falls.
Bicolor Standards are a different color than the falls.
Bitone Standards are a lighter shade of color than the falls.
Neglecta Blue or purple bitones with standards a lighter shade of the color of the falls.
Reverse bitone A bitone with the standards a darker shade of the same color as the lighter falls.
Blend Combination of two or more colors, can be smoothly or unevenly mixed.
Variegata Yellow standards and maroon or brown falls.
Plicata Stippled, dotted, or stitched margins of anthocyanin pigmentation on lighter ground color.
Luminata The reverse pattern of a plicata, with darker ground color and white edges, veins and around beards.
Glaciata These lack all anthocyanin pigments and are pure whites, yellows, pinks, or oranges, formerly called ices.
Substance Thickness and resilient tensile strength of the flower parts.
Texture Surface sheen or finish, such as velvety or satiny finish of the petals.
Diamond dusted Tiny, conical raised areas across the petal surface that shine like diamonds in the light.
Silver lining Standards and falls have raised areas on the edges that reflects light in a shining light.
Wash Obvious or definite overlay of one color on another.
Infusion Faint or subtle overlay of one color on another.
Sunburst White or light streaks fanning out on the falls around, and sometimes beyond, the beards.
Spot Darker area around and below the beard on lighter or different colored falls.
Signal An area or patch of contrasting color below the beards (usually on arils, and some beardless varieties).
Zonal A distinct white or light area around the beards in the middle of the falls.

© 2013 Median Iris Society -- All Rights Reserved


Last updated: January 13, 2023