Flowers in the iris genus are derived from nearly 300 species and have been cultivated into thousands of diverse, colorful varieties. They range in height from 6 inches to 3 feet and vary in hardiness between zones 3 and 11. Irises can be annuals or perennials, depending on your region and maintenance.
With firm, strappy leaves and full-throated, face-like blooms, iris flowers are easy to spot in the late spring or early summer landscape. Look for scalloped or sheared petal edges in a three-up, three-down bloom arrangement at the top of thick, sturdy stems. Some will even have fuzzy, caterpillar-like ‘beards’ near their centers.
Determining the likeliness of their return next year depends on where you live and which species you plan to plant. Read on for an in-depth look at the iris flower’s official plant classification and the difference between an annual, biennial, and perennial plant. We’ll also explore some situations where the lines might be blurred.
Irises are technically perennial plants, which means they will go dormant in winter and return for at least one more growing season. Remember that this is true only for irises planted within their recommended hardiness zones or for out-of-zone irises brought inside to overwinter. When properly planted and cared for, an iris can be expected to return perennially for somewhere between 5 and 20 years.
All herbaceous, flowering plants exist to perpetuate themselves in some way. And each falls into one of three life cycle categories: annual, biennial, or perennial. Before we determine which group includes the iris, it helps to understand the differences between them. Here’s a quick breakdown:
Plants in this category will complete their life cycle in a single growing season. This means a seed will sprout, grow, bloom, produce more seeds, and die in the same year.
Although seeds from some annuals can be collected, stored, and planted next year, they will not likely produce new plants without human intervention. Hybrids are unlikely to produce true-to-type seeds, meaning they don’t contain the hybridized DNA that made their parent plant beautiful and may revert to prior genetics once planted.
Annual plants will typically flower all season if properly deadheaded and are often selected to provide constant color. Zinnia, marigold, petunia, begonia, and impatiens are all true annual plants that many of us pop into pots and beds each year, accepting their short lifespan as part of the deal.
Sometimes, we treat a perennial plant like an annual, allowing it to die at the end of the season as if it were a one-and-done thing. Gardeners might pop some tulips into a porch pot and pull them out when they’ve finished flowering, or use a perennial grass as a container thriller, knowing it won’t survive the cold winter with its roots above ground.
Plants in this category will complete their life cycle during two growing seasons. In their first year, they produce roots, stems, and leaves but will not bloom.
In the second year, they’ll produce flowers and seeds before dying at the end of the season. Those seeds will typically self-sow and produce new vegetative plants the next season, and the cycle will continue until it’s interrupted.
Examples of biennial plants include parsley, dill, carrots, bellflowers, and forget-me-nots. There are also many biennial weeds, including burdock, Queen Anne’s lace, and thistle. Biennial plants typically thrive in temperate climates, where seasons change predictably, and the highs and lows are not extreme.
Plants in this group will live for at least two growing seasons. The leaves and stems above ground will die back completely after the first freeze, but their roots will persist and survive below the soil surface. Perennial plants will produce new leaves, stems, and flowers (if applicable) each spring.
While some perennial plants flower enthusiastically for just a few years (coral bells, delphinium, lupine, columbine), others can potentially flower for decades (peony, hosta, daylily, and yes, iris!). Flowers in this group typically reproduce through root expansion below ground and must be divided regularly if you want them to keep coming back.
Do Iris Bloom Every Year? A Guide to Getting the Most out of Your Irises
Iris are a popular perennial flower that can provide colorful blooms in the garden year after year. But some gardeners find that their iris stop blooming or have reduced flowers over time. So do iris bloom every year?
The short answer is yes iris are perennials capable of blooming annually when planted and cared for properly. However there are a few key factors that affect iris blooming frequency and intensity that are good to understand.
Iris Bloom Cycle
Iris are programmed to go through an annual bloom cycle that is influenced by seasonal changes in temperature and light
In temperate climates, the bloom period for most iris is in spring or early summer. Blooming starts with the emergence of a tall flower stalk from the base of the plant Buds gradually open into gorgeous blooms that last 7-10 days on average
Once the flowers fade, seed pods may form before the flower stalk dies back entirely. The foliage remains to soak up sunlight and deliver energy to the underground rhizomes for next year’s bloom.
This natural bloom cycle means that well-established, healthy iris should flower every year. However, issues like overcrowding, improper planting depth, insufficient sunlight, pests, and diseases can disrupt the bloom cycle.
Maximizing Iris Bloom
Here are some tips to maximize bloom and keep your iris flowering happily year after year:
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Plant in full sun (at least 6 hours direct sun per day). Morning sun is ideal.
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Choose a spot with well-draining soil. Avoid overly wet, soggy locations.
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Plant the rhizomes shallow, with tops slightly exposed. Don’t bury too deep.
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Space rhizomes 12-24 inches apart to prevent overcrowding over time.
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Water 1-2 times per week if rainfall is insufficient, avoiding wet foliage.
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Apply a balanced fertilizer early in the season to support blooming.
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Divide congested clumps every 3-4 years to rejuvenate the plants.
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Cut off spent flower stems near the base after blooming finishes.
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Leave foliage intact through summer until it dies back naturally.
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Remove dead leaves and debris in fall to prevent pest/disease issues.
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Watch for signs of common iris problems like borers and root rot.
With good growing conditions and proper care, iris will bloom heavily in spring and early summer, take a short rest, and then start preparing for the next year’s bloom.
Why Iris Fail to Bloom
If your iris aren’t blooming consistently or the bloom intensity has declined, there are a few common culprits to investigate:
Overcrowding – Iris clumps that get too congested will bloom less and less over time. Dividing and replanting the rhizomes gives the plants room to grow and bloom their best.
Insufficient Sunlight – Without adequate sunlight (at least 6 hours/day), iris won’t get enough energy to produce substantial bloom. Relocate to a sunnier spot if needed.
Excess Shade – Nearby trees and shrubs that have grown and started shading your iris can limit bloom. Prune or remove encroaching plants to restore sunlight.
Improper Planting – Irises planted too deep fail to bloom well because the buried rhizomes rot. Replant at proper shallow depth.
Overwatering – Excess moisture leads to root rot and other problems that reduce flowering. Allow soil to dry out between waterings.
Underwatering – Insufficient water during growth and blooming causes stress that inhibits flowering. Maintain even moisture.
Poor Drainage – Standing water from heavy clay soil, runoff, or poor drainage stresses iris and severely limits bloom. Improve drainage.
Nutrient Deficiencies – Soil depleted of nutrients after many years may not support vigorous blooming. Fertilize according to soil test results.
Pest Damage – Borers, thrips, and other iris pests can damage plants enough to limit flower production. Treat any infestations.
Diseases – Bacterial or fungal problems like iris leaf spot and soft rot can weaken plants and reduce flowering. Address any disease issues promptly.
Harsh Winters – Extreme cold without reliable snow cover may damage plants, impacting subsequent blooms. Use winter mulch in very cold climates.
With a little troubleshooting and adjustments to care, most iris bloom issues can be corrected and your plants can regain their ability to flower abundantly every season.
Special Iris Types
While most iris are spring bloomers, there are some fun exceptions like:
Reblooming Iris – Certain “remontant” iris varieties can be coaxed into blooming again in late summer with proper care. Fertilize and trim spent blooms to encourage rebloom.
Winter Iris – Unusual varieties like Iris unguicularis bloom in late winter, providing early season color. Give them drier conditions in summer.
Evergreen Iris – Iris like I. japonica stay green year-round and can bloom sporadically on and off through the seasons.
African Iris – Tropical Dietes iris bloom spring through fall, taking short breaks in between. Tolerates more shade and humidity.
Experiment with special iris types if you want to extend the bloom season in your garden. But focus first on getting your spring-blooming bearded iris flowering reliably each year. With a little TLC, a bed of classic iris can provide gorgeous color and fragrance annually for decades to come. The key is understanding their growth habit and bloom requirements so you can provide the right care.
Do Iris Bloom Every Year: Final Thoughts
Iris are programmed to complete their bloom cycle annually and flower profusely each spring or early summer. But issues like overcrowding, improper planting, insufficient sunlight, pests, diseases, and unfavorable weather can disrupt the natural rhythm and limit flower production.
Fortunately, iris are tough plants that will bloom dependably year after year when their basic needs are met. Provide full sun, well-drained soil, adequate water, occasional fertilizer, and division every few years, and your iris will thank you with a beautiful annual floral display. Pay attention to proper planting, pest prevention, and timely division, and your iris will keep blooming season after season.
The Iris Life Cycle
Irises vary significantly in hardiness, meaning not all varieties grow as perennials in all zones. For example, if you plant a heat-loving Louisiana iris in chilly Minnesota, you’re not likely to get a return on your investment. Louisiana species can only tolerate the average low temperatures of zones 6 through 10. Plant one in a cold northern state, and it will most likely freeze to death.
Conversely, a hardy Dutch iris from zone 5 to 9 will probably die from heat stress if planted in southern Mexico. So pay attention to the nursery tags and select the right iris for your part of the world if you’d like it to behave like a true perennial.
Of course, if you’re satisfied with just one season of blooms (which, for most iris varieties, is a fleeting period of 2 to 3 weeks), you may treat perennial irises like they are annual flowers and dispose of them at the end of the season. Irises lend themselves well to spring container arrangements because their foliage provides an enduring, spiky focal point. Plus, they flower just when the tulips are done.
To bring cold-sensitive irises back next year, dig them up at the end of the season and store them carefully. Alternatively, drag your container to a cool, dry location where you can monitor them throughout winter. Otherwise, they’ll meet the same late-season fate as the ‘real’ annuals in your yard.
Why Don’t Iris Bulbs Bloom Every Year?
FAQ
Why did my iris not bloom this year?
Several factors can prevent iris plants from blooming, including insufficient sunlight, improper planting depth, overcrowding, and lack of division.
How often does an iris bloom?
Will iris come back every year?
Low maintenance: Once established, irises require minimal maintenance, making them a great choice for busy gardeners. Perennial: Most iris varieties are perennial, meaning they will come back year after year with proper care.
What is the lifespan of an iris?
Bearded iris, Iris germanica, is one of the most easy and rewarding perennials you can grow. They can survive in xeric gardens with as little as 10 inches of rainfall a year, and will grow and bloom without care as long as they get plenty of sun. Multiplying perpetually, there is no limit on a bearded iris’ lifespan.