The Iris is one of the most beloved and popular garden plants. Evidence shows it’s been used as a garden plant in ancient Egypt by King Thutmose III in 1469 B.C. In the Greek language the word “iris” means rainbow. And Iris can be found in nearly every color of the rainbow, except for true red.
The genus Iris is a member of the Iridaceae family and contains about 300 species. The family includes Freesia, Gladiolus, and Crocus.
Iris grow wild on almost every continent in nearly every climate condition. They grow from watersides and swamps to high mountainous areas and deserts. Most species of Iris (its scientific and common name) are perennial plants growing on creeping rhizomes and producing showy flowers. Home gardeners typically grow popular hybrids of these amazing plants.
Rhizomes and Bulbs
The main differences between bulb iris and rhizome-type iris are how they grow, the size of their flowers, and when they bloom. In general, rhizomatous iris produce larger flowers and bulb iris produce smaller flowers and bloom earlier.
Bulbs – Bulbs have underground structures in which they store their nutrient reserves. Common flowering bulbs include tulips, daffodils, hyacinths, amaryllis, lilies, and Dutch Iris.
Rhizomes – A rhizome is a modified, horizontal underground plant stem. It grows sideways and sends out roots downwards and sends shoots upwards. The modified plant stem acts as a storage organ for nutrients. Rhizomes grow near or above the soil.
Types of Iris
There’s an Iris for every habitat. To know what will grow best in your garden, check your Plant Hardiness Zone. The United States Department of Agriculture (USDA) maintains the zone map. They adjusted the map in 2023 to reflect warmer winters. If you haven’t checked your zone since then it may have changed.
Find your Plant Hardiness Zone by Zip Code.
Winter Hardiness – Bearded Iris, Siberian Iris, and Japanese Iris are winter hardy in zones 3-9. The Beardless Iris, Reticulated Iris, and Dutch Iris are hardy in zones 5-9. Louisiana Iris are hardy in zones 6-9.
Other factors besides winter hardiness determine how well plants do in your garden. Soil type, rainfall, humidity, and more will also impact how plants grow. Even within your garden, you’ll likely find microclimates that affect plant growth.
Bearded Iris
The most commonly grown iris by our members is the Bearded Iris. The flowers have three upright petals called standards and three cascading petals called falls. They have a row of fuzzy hairs, called beards, at the top of each fall. Easy to grow and beautiful to look at, there are over 30,000 cultivars of bearded iris.
Beardless Iris
These iris are grown from rhizomes, lack beards, and generally need a lot of moisture for good growth.
Arilbred Iris
Arilbred (AB) Iris are produced by crossing the Aril Iris with the more common bearded iris.
Bulb Iris
These iris are all grown from bulbs. They produce smaller flowers than bearded iris. Most are best for rock gardens or in front of the border.
