Irises are some of the most popular flowers in any garden. Their bright blooms have been loved for hundreds of years, which is why they’re so popular. As a gardener, nothing is more frustrating than when these hardy perennials don’t put on their usual spring flower show.
If your irises aren’t blooming, don’t despair. In most cases, the problem is easily fixed. Irises don’t bloom all the time for these reasons. Here’s what you can do to get them to bloom again next year.
Overcrowding
This is one of the most frequent causes of irises not blooming. Irises spread rapidly via rhizome growth under the soil. Over time, they can become severely overcrowded which stresses the plants.
Irises don’t get enough sunlight, water, or nutrients when they are crowded. Because of this, they have to save energy instead of using it to flower.
The solution is simple – it’s time to divide your irises. This should be done every 3-4 years anyway. Carefully dig up the entire clump and cut apart the rhizomes. Replant the healthiest rhizomes 18-24 inches apart.
Dividing overcrowded irises not only rejuvenates them so they bloom again it also gives you more plants!
Improper Planting Depth
It is also very common to plant the rhizomes too deeply. Irises should be planted very shallowly, with the tops of the rhizomes just below or just above the soil.
When planted too deeply, the rhizomes can rot from excess moisture. They also don’t receive enough sun to fuel growth and flowering.
Check your planting depth and remedy it if needed. When transplanting, mound the soil up to just barely cover the tops of the rhizomes. This allows proper drainage and air flow.
Insufficient Sunlight
Irises thrive best in full sun – at least 6 hours of direct sun per day. With less light, you may get some flowers, but the display will be reduced.
If your irises aren’t blooming well, assess whether they’re getting sufficient sunlight. Nearby trees or shrubs may now be shading the area too much. If so, prune back encroaching growth.
Alternatively, you can transplant the irises to a sunnier spot. Just make sure it has well-draining soil. Morning sun is ideal as it dries the foliage, reducing disease risk.
Under or Over Watering
Though tolerant of drought once established, irises still need adequate moisture to fuel growth and flowering. In spring when the flower stalks are emerging, water if rainfall is insufficient.
But take care not to overdo it either. Soggy soil leads to rhizome rot. The area should have good drainage. Water deeply only when the top few inches of soil become dry.
Reduce watering after bloom and allow soils to dry out more in summer. This encourages the rhizomes to go dormant. Renew regular watering in fall.
Excess Fertilizer
Heavy fertilization with nitrogen creates lush foliage growth at the expense of flowers on irises and many other plants. Go easy on the fertilizer and use one higher in phosphorus than nitrogen.
Slow release organic fertilizers are ideal, applied early in spring. You can also work in some bone meal when replanting. But don’t overdo it.
Cutting Leaves Too Soon
Some gardeners mistakenly trim off the iris leaves after flowering. But the foliage needs to remain intact for at least 6-8 weeks after blooming to nourish the rhizomes for next year’s flowers.
So resist the urge to prematurely prune off the unsightly dying leaves. Leave them be until they yellow entirely. Then you can remove them to tidy up the garden bed.
In most cases, correcting one of these common issues will have your irises blooming beautifully again. Pay close attention to overcrowding, planting depth, sunlight and watering. Avoid over fertilizing. Leave the foliage intact after blooms fade.
With a little TLC, you can get your irises back on track to give a stellar performance next spring. The work is well worth it to enjoy those delightful flowers once more!
Your irises are too crowded.
Let’s start with the most common cause of irises not putting out flower stalks – they’ve grown too crowded. There’s a simple solution to this problem: you can divide your irises into several clumps and replant them.
If you want to prevent the disappointment that comes with overcrowded plants, you should divide your irises every three to four years by default. You can go longer between divisions if you’re gardening in a cooler climate, but you’ll most likely need to divide more frequently if you’re in a warm, humid climate where your irises are bound to grow faster.
For a full tutorial for dividing and replanting irises, we’ve got you covered here.
If you’re ready to replant your newly-divided rhizomes, let’s move on to the next point on our list to make sure you maximize their chances of getting irises to bloom in the future.
Your irises need more sun.
You’ll be able to grow lush iris foliage in the shade, but don’t expect too many flowers.
In order to bloom, irises should be getting at least six to eight hours of full sunlight. In climates with extreme heat, they’ll need some afternoon dappled shade to keep them from getting scorched. But as a general rule, the more sun they get, the better.
That’s why you should try to plant your irises in an open space. You may have done this when you first chose their location initially but, over time, other surrounding trees, shrubs or manmade structures may have started to cast a shade over your irises.
Irises don’t like to compete with stronger surrounding plants or trees, both in terms of light and water needs, so pairing them with plants that have the same requirements (such as daylilies) is your best bet at keeping them happy.
If you’re not sure how much sun your irises are getting, pick a sunny day in mid-spring to early summer and, starting in the morning, record every hour on the hour if sunlight is reaching the spot where your irises are planted.
Moving your irises to a spot that gets as much sunlight as possible is the easiest way to fix this problem, though it might not be the only way.
7 Reasons Why Your IRIS is NOT Blooming |#gardening
FAQ
How do I get my irises to bloom?
Shade and overcrowding are the most common culprits when irises won’t bloom. If your irises aren’t in full sun, move them to a brighter spot.
What month do you cut back irises?
You can cut back iris at any time, like right before or after a killing frost, or in late fall if you live somewhere warmer. However, should you find yourself in a position to cut them back now. it’s ok to do so.
Why are my irises not blooming?
Your irises are planted too deep. Hopefully, dividing your irises will encourage new blooms. If you’re used to planting spring bulbs, there is a trick to (re-)planting irises that might not make sense. The second most common reason why irises fail to bloom is because they’ve been buried too deep.
Why do Iris have no flowers?
Most species of iris spring from rhizomes, although a few come from bulbs. Both these are underground storage structures that contain a reserve of carbohydrates and embryonic plants. When temperatures and lighting are right, they sprout stems and leaves and eventually produce flowers. Poor rhizomes or bulbs are often the cause of no flowers.
Do Iris bloom every year?
Depending on the variation of your iris you may also have a species that does not bloom every year. The common bearded iris is dependable and will bloom between March to May. The Siberian Iris blooms later in the season. I have found the iris to be a hardy plant that is often resistant to insects and fungus.
Can iris plant not flowering solutions?
If your Iris plant isn’t flowering, make sure you plant it so that the top of the rhizome is just below the soil surface. This will offer them adequate protection while allowing for proper development. During the peak of summer, your Iris plants might be feeling the heat – literally.
Should I leave Iris leaves intact after blooming?
You should leave the iris foliage intact once the blooms are spent. That’s because the plant needs the leaves to stay attached as long as possible to soak up the sun which is much-needed for photosynthesis to take place. This helps the rhizomes store energy for next year’s bloom.
Do Iris grow clumps?
Irises have a clumping growth habit. They spread via rhizomes and self-sown seeds. Over time, the garden will likely become overcrowded, a condition that causes competition for food and water. The solution is to divide large iris clumps in late summer to early fall, well past blooming and ahead of the first frost.