As a child growing up in the mountains of Western North Carolina, I thought irises were part of the orchid family because their blooms were just as spectacular and exotic. I would find native irises in the woods along stream beds, and every home had a garden full of bearded irises in Easter egg colors. As you discover your favorite cultivar of irises, it’s good to know when they will bloom so you can enjoy the show.

Types of Irises and Their Blooming Seasons

Bearded Irises (Iris germanica)

One of the easiest perennials to grow in the garden, bearded irises offer a wide variety of flower colors and plant sizes to create an interest in a perennial border. Grown from rhizomes, the plant has large, sword-shaped, upright foliage. Name a color from black to purple to yellow to white and almost any variegation, and you can find a bearded iris that fits. The fragrant flowers appear as a single bloom or a cluster on a long, tall stem. Depending on the cultivar and your climate zone, bloom time can be from late March to mid-June in the South.

Dwarf Irises (Iris reticulata)

Dwarf irises are one of the earliest blooms in the spring, with deep violet to blue flowers highlighted by white, silver, or gold markings. Their petite size, just 4 to 6 inches tall with grass-like foliage makes them the perfect companion to crocus and early-blooming daffodils. The bulbs are best planted in the fall. They naturalize and should be divided about every five years. Expect to see dwarf iris blooms in late February through March in the South.

Dutch Irises (Iris hollandica)

Grown from a bulb planted in the fall, a Dutch iris has a more delicate bloom than a bearded iris and thin, strap-like leaves that overlap at the base. Prized as cut flowers, each stem has one to three buds and colors from purple to blue to yellow to white. The flowers appear in mid-April to late May in the South.

Factors Influencing Blooming

Irises prefer loamy, well-draining soil to prevent root rot and keep the plants healthy. While the soil should be kept moist, the plants should not be heavily mulched to preserve soil moisture or watered so heavily that they become waterlogged. While dwarf irises can tolerate some shade, bearded and Dutch irises require at least 6 hours of full sun daily to bloom well.

To encourage growth and blooming, dwarf and Dutch irises require more fertilizer than bearded varieties. Take a soil sample and have it tested to determine fertilization needs. Or, use a balanced NPK fertilizer like 10-10-10 for a light application in early spring and then again about a month after the plant stops blooming. When fertilizing a bearded iris, apply the fertilizer around the rhizome cluster, not directly on it.

If the iris is not blooming as profusely as it once did, dig up the blub cluster or rhizome clump and divide it once blooming is complete. Replant and fertilize the area lightly.

Extending the Blooming Season

Deadheading or promptly removing faded flower spikes will encourage the formation of new flower buds during the spring season.

To extend the iris season, plant iris varieties with staggered bloom times or plant bearded iris varieties that rebloom. Reblooming varieties are heavy feeders that require more water and fertilization to rebloom in late summer or early fall.

• ‘Again, and Again’: (zones 5-10): bright yellow
• ‘Clarence’ (zones 5-10): white center over violet lower petals
• ‘Immortality’ (zones 3-10): white
• ‘Matrix’ (zones 4-10): cream with cinnamon edges
• ‘Pink Attraction’ (zones 5-10): ruffled pale pink
• Plum Wine (zones 5-10: dwarf plum-red
• ‘Silver Dividends’ (zones 6-10): ruffled silver-white
• ‘Sunny Disposition’ (zones 5-10): light yellow
• ‘Violet Music’ (zones 5-10): violet
• ‘Zurich’ (zones 5-10): ruffled white with yellow-tipped beards

Troubleshooting Non-Blooming Irises

Common issues and solutions

Water: Too much moisture from overwatering or poor-draining soil will cause bulbs or rhizomes to rot and stop blooming.

Light: Irises need full sun (6 hours daily) to bloom well.

Soil: Irises planted in clay or heavy soil will not bloom well due to excess moisture.

Fertilization: Irises need nutrients to produce blooms. Apply a balanced fertilizer in early spring and again about a month after the blooms have faded.

Overcrowding: If a stand of irises stops blooming well, it is time to divide the bulb cluster or rhizomes. Division should be done after the blooming cycle is complete and foliage has started to yellow, usually in July. For dwarf and Dutch irises, dig up and separate bulblets from the mother bulb every five years. Divide and transplant bearded iris rhizomes every three to four years. If the plants are reblooming bearded varieties, you will not get a rebloom in the fall after division but they will bloom again in the spring.