Horticultural Classification

There are two classification systems; Botanical Classification and Horticultural Classification. As the world's registrar for Iris The American Iris Society has developed certain horticultural classifications based on the plants use in the garden. They include all the categories seen on the main page of this Encyclopedia. They are also listed below:

They include 6 classes of bearded Irises divided by height and size;
  • (TB) Tallbearded Irises (over 27 inches (68 cm))
  • (BB) Border Bearded Irises (16 to 27 1/2 inches (41-70 cm) blooms with TBs
  • (IB) Intermediate Bearded Irises (16-27 inches (41-70 cm)) with bloom period between SDB and TB
  • (MTB) Miniature Tall Bearded Irises (16-25 inches(41-63 cm)) bloom with or slightly ahead of TBs
    • Flowers not more than 15 cm (6 inches) combined height and width: born on slender, wiry, flexuous stalks 3-5 mm (1/8 to 3/16 inch) wide directly under the flowers and increasing gradually to about 16 mm (5/8 inch) at ground level
  • (SDB) Standard Dwarf Bearded (20-40 cm (8-16 inches))
  • (MDB) Miniature Dwarf Bearded Irises up to 25 cm (10 inches) or 20 cm (8 inches)
    • note size has been redefined several times through the years.
Also 2 bearded classes with aril genetics:
  • (AR) Arils which are solely developed from Species and hybrids of species within the Botanical Sections having arillate seeds; Primarily Sections Oncocyclus and Regelia
  • (AB) Arilbreds which are genetically hybrids between the Aril sections and the bearded Irises above that all fall into the botanical Section Iris formerly know as Eupogons.
Also 5 beardless groups: (the archaic term Apogon is often used for beardless) Also 2 Special classes; (SPEC),Species and (SPEC-X), Species Crosses

(SPEC) Species as a horticultural class are equivalent to botanical species and their variations. Grown in gardens these variations are termed cultivars, and may show unusual characteristics distinct from the botanical Type. Species are obviously at the root of all the above classes and those classes as in the case of the Japanese may have developed plants that although botanically still the species may look very different from the wild flowers known by that name. The horticultural class includes:
  • Species that do not fall in the above refined classes or
  • Plants or a species that may be at the origins of the above classes but still seem more like a wildflower than the paradigm of the developed class.
(SPEC-X) Species crosses are hybrids. But not all hybrids fit into the horticultural classes above. All the hybrids in the above horticultural classes would have been considered SPEC-X until a subgroup builds large enough that a new more narowly defined class is created. SPEC-X horticultural class may be considered the testing ground for new forms of Iris created by new combinations of species. It provides a place for plants that are creating a new category so that the efforts can be noticed and recognized.

Chronologically the SPEC and SPEC-X were the last of the horticultural classes to be created, such that no Iris would be left out of a classification. But logicaly These two classes are the beginning of all the subsequent derivative classes. Since all derivative classes overlap with either SPEC or SPEC-X and some of the derivative classes overlap with each other it is left to the registrant to pick the class that would represent the iris best.


-- Main.RPries - 2010-02-04
Topic revision: r6 - 18 Feb 2016, af.83
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