A breadth of colors is likely to explain why certain plants are called Iris, a term deriving from the Greek word for “rainbow.” (The ancient Greek goddess of the rainbow was also given this moniker.) With the profusion of colors found in cultivated varieties of Tall Bearded Iris alone, it is not difficult to explain the association between these flowering plants and the spectacular spectrum that stretches across the sky.

Beyond color variety, however, there is an even larger world in which Iris demonstrate an array of shapes, forms, habits, and idiosyncrasies. Follow along as we explore this diversity, with the hope it may inspire a greater appreciation of a remarkable genus.

Understanding Iris

To set the stage for the genus Iris, which comprises almost 300 species, it helps to step back to view it within the wider context of its botanical family. The Iris family (Iridaceae) includes 64 other genera also known as “Irids” — brothers and sisters, if you will, of our beloved Iris. The family tree contains well-known siblings like Crocus, Freesia, and Gladiolus, plus a plethora of lesser-known relations, from Aristea to Zygotritonia. With such an extensive family, it may be easier to understand why Iris species manifest such a variety of characteristics.

The American Iris Society, the world’s registrar for Iris, upholds some essential classifications to help make sense of this broad genus. One of the simplest groupings depends upon the structure of the plants’ underground parts where nutrients are stored. Some of the most well-known Iris grow from rhizomes — modified stems that grow horizontally in the soil and send out roots and shoots from nodes. Examples of rhizomatous Iris include the flamboyant Tall Bearded Iris (Iris germanica) and flat-flowered Siberian Iris (I. sibirica). Other Iris come from bulbs, just as Tulips and Daffodils do. Some bulbous species are Dwarf Iris (I. reticulata) and Dutch Iris (I. hollandica). A final category includes plants with fleshy roots, such as Juno Iris, a subgenus comprising multiple species.

A more technical classification method, which can make identifying Iris varieties easier at a glance, is based on floral structure — specifically, whether a fuzzy “beard” is present on the flowers’ lower petals, called “falls.” Bearded Iris and Beardless Iris both have their own unique types. A couple of other categories are of special interest to botanists (and will not be highlighted here). Perhaps of more relevance to gardeners are the informal groups organized around Iris characteristics of horticultural value, such as reblooming, unusual foliage, and historical status.

Flight of Floral Forms

Iris flowers are not just extraordinary for their range of colors. They are also structurally stunning — from showy Tall Bearded Iris flowers with their billowing standards (upright petals), lavish falls, and textured beards to the distinctly prostrate, beardless blossoms of Siberian Iris and Japanese Iris (I. ensata). To create a sequence of bloom in the garden, pair the June-flowering Tall Beaded Iris and Siberian Iris with Japanese Iris, which blossom slightly later. The examples below illustrate the possibility of a prolonged period of bloom with a procession of varying shapes and forms.

The muted shades of bicolored Tall Bearded Iris ‘Champagne Elegance’ invite us to focus a bit more on the graceful cadence and delicate ruffles of the ivory standards and palest orange falls. This prolific bloomer carries 7–10 buds per stem. It is also a favorite example of Reblooming Iris, a type that may, in favorable conditions, send forth a second round of flowers in late summer.

Iris chrysographes black-flowered, a kind of Siberian Iris, is stunning for its deep reddish violet blooms that appear as dark as night. It is also called the “Gold-Marked Iris” (literal meaning of chrysographes) for the fine pattern of golden tracery at the top of the falls. With a trio of standards much smaller in ratio to the falls, as well as three prominent “style arms” among the standards, this beardless blossom has quite a contrasting countenance to that of its relation above.

The luxuriant purple flowers of Japanese Iris ‘Loyalty’ measure almost 8” across. Unlike the former two blooms, this one is noteworthy for the six equally sized petals that cascade in unison from the base of three modest, upright style arms. ‘Loyalty’ adds individual flair with bright yellow striping that emanates from the petal throats, accentuating the detailed, blue-violet veining across the petals themselves.

Beyond Blooms

While the flowers alone point to great diversity within the Iris genus, there are other characteristics that set it apart. Two of them include growth habit and leaf color.

This dwarf variety of Crested Iris (Iris cristata), ‘Eco Bluebird,’ is praiseworthy for more than just its lilac-blue flowers that bloom in mid-spring and are attractive to hummingbirds. Reaching only 6-8” tall, it makes a perfect ground cover in a wide range of soil conditions.

Iris pallida ‘Variegata Aurea,’ a variegated variety of Sweet Iris, is a favorite for lavender blooms that happen to possess the unforgettable scent of grapes. But this plant could also be grown simply for its foliage. The golden striped leaves beautifully echo the yellows of companion plants and appear to be aglow when backlit by sunshine.

No matter why you decide to plant Iris in your garden, one thing is certain. There are manifold reasons to add members of this genus to your collection of plants. Indeed, the infinite variation of Iris may be the pot of gold at the rainbow’s end.