It's a magical time when bearded iris flowers unfurl their pencil-slim buds to reveal a kaleidoscope of color, beginning as early as March in warmer regions. Depending on the type of bearded iris, they can be in bloom all the way into June. Some types even rebloom in late summer and fall. These hardy perennials flourish in USDA Zones 3-9, where winter temperatures dip below freezing and allow the plant to go dormant before next year's growth.
"Anyone can grow iris," says Doris Winton, who has had a lifelong attraction to this plant and is a master judge for the American Iris Society. It's easy to understand why people have such passion for iris—it's a very diverse group of plants, with bearded iris being one of three main categories. This kind of iris is so named because of a patch of soft bristles on the lower petals of the flowers. In addition to their long bloom time, bearded iris come in an incredible variety of colors and patterns. "Every color—except fire-engine red—can be found in bearded iris," Doris says.
No matter which varieties you choose to grow, there are a few things you can do to help them thrive in your garden.
Iris Growing Tips
- Plant them in a sunny spot in late summer. The plants need well-drained soil and at least six hours of sunlight per day. A full day of sun is even better to keep the rhizomes dry. (The rhizomes are the fleshy rootlike structures at the base of the plant.)
- Prepare their beds. Use a low-nitrogen fertilizer and apply it twice a year—in early spring and just after bloom when the rhizomes are forming the next year's flowers. Water only if it is extremely dry or after transplanting.
- Give them room to breathe. Bearded iris require good air circulation. Plant them a minimum of 16 to 18 inches apart (less space for dwarf irises and more for tall bearded iris varieties).
- Do not mulch. Mulching retains moisture, and too much moisture will cause the rhizomes to rot.
- Remove seedpods that form after the blooms have faded. This prevents seedlings from choking the surrounding soil. Seed formation also saps energy needed by the rhizomes, roots, and leaves.
- Prune back the foliage in the fall. This will reduce the chances of overwintering pests and diseases.
- Make dividing a habit. Divide clumps of bearded iris plants every three to four years in late summer.
How to Divide Bearded Iris
Bearded iris grow from a thick, rootlike structure called a rhizome. As the plant matures, the rhizome produces more rhizomes, which in turn lead to more leaves and flowers. Over time, however, the original rhizome withers and dies off. When this happens, bloom production slows and it is necessary to divide the plant, removing and replanting the newer rhizomes so they have the space they need to fully develop.
Bearded iris should be divided in the late summer when the weather starts to cool. The division process illustrated below can be used for other plants that produce rhizomes, including canna, bergenia, dahlia, toad lily, and lily-of-the-valley.
Step 1: Dig Up Clumps
Carefully dig the clumps with a garden fork or spade, taking care not to chop into the rhizomes more than necessary.
Step 2: Break Apart Rhizomes
Divide the rhizomes by pulling them apart with your hands. In some cases, you may need to use a sharp knife to separate the smaller rhizomes from the main one. If so, dip your knife into a 10-percent bleach/water solution between cuts so you don't spread any diseases to new rhizomes.
A good rhizome will be about as thick as your thumb, have healthy roots, and have one or two leaf fans. Large, old rhizomes that have no leaf fans can be tossed out.
Step 3: Rinse and Evaluate Rhizomes
Wash the soil off the rhizomes to that you can inspect each one for iris borer (a plump, white worm). If you find a borer, destroy it. Some gardeners like to wash their iris rhizomes in a 10-percent bleach solution to protect against disease, but that won't help plants that are already rotting. Make sure to discard any soft, smelly rhizomes you find, as well as any that feel lightweight or hollow, or appear dead, like the rhizome shown above.
Step 4: Cut Leaves
Clip off the leaf blades so that they're 4 to 6 inches long. This reduces the stress that the plant goes through as it concentrates on regrowing new roots instead of trying to maintain long leaves.
Step 5: Plant Divisions
Replant divisions, setting the rhizome higher in the planting hole than the fine roots, which should be fanned out. A bit of the top surface of the rhizome should be just visible at the soil surface.
Step 6: Plant Remaining Rhizomes and Water
Space the plants 12 to 18 inches apart (closer for dwarf varieties, farther apart for the largest). For the best display, plant the rhizomes so the fan of leaves face the same direction. Water well when planting bearded iris rhizomes, but do not continue to water unless the weather becomes dry.
'Fringe of Gold' bearded iris
Great Bearded Iris Varieties
Iris flowers have three primary structures, and descriptions of a variety often refer to these parts. For example, in the 'Fringe of Gold' flower shown above, the drooping "falls" are white-edged (or picoteed) in yellow. The upright "standards" are solid yellow. And the tiny fuzzy "beard" in the middle is white and yellow. You can use these structure names to imagine how an iris might look when you have only a text description.
As a longtime lover of bearded iris, Doris Winton has many favorite varieties, including 'Fringe of Gold'. See below for several more of her favorites.
This variety is a dwarf tall bearded iris with yellow blooms. The petals have a white and deep purple veined pattern that makes for a bold contrast on each bloom. Plant these irises in full sun. Zones 3-8
'Bumblebee Deelite' Dwarf Bearded Iris
This variety is a dwarf tall bearded iris with yellow blooms. The petals have a white and deep purple-veined pattern that makes for a bold contrast on each bloom. Plant these irises in full sun. Zones 3-8
'Rebecca Perret' Bearded Iris
White petals fade into light purple on the tips on this softer bearded iris variety. The mid-height selection can thrive in full to part sun. Zones 3-8
'Perfect Pitch' Bearded Iris
'Perfect Pitch' is a true purple bearded iris that has ruffled petals. This cultivar does best in full sun and is considered a tall variety. Zones 3-8
'Ozark Dream' Dwarf Bearded Iris
If you love purple, 'Ozark Dream' is the bearded iris for you. The top petals of the bloom are a light purple, while the falls are dark violet. Plant this cultivar in full sun. Zones 3-8
'Latin Hideaway' Bearded Iris
This tall bearded iris variety has a large contrast between the top petals (which are white) and the falls (in a brick red hue). The red falls petals have a hint of magenta near the center, and the inside of the white petals has a light pink hue. Zones 3-8
'Gallant Moment' Bearded Iris
The scarlet blooms of this bearded iris variety make it stand out in the garden. The petals fade into orange and gold tones toward the center of the bloom. The outer edges of the petals become such a dark red that they almost look chocolate brown in places. Zones 3-8