With more than 300 species, most of which do very well in gardens, the iris is one of the most popular flowering plants. They grow out of bulbs, and they bloom fairly early, sometimes as early as March, while there are also varieties that bloom twice a year.
However, what if you can’t get your iris to bloom? What if, for some reason, the year passes and your iris never shows its flowers?
There are exactly 7 common problems that prevent irises from blooming, but there are also solutions to each of these problems, so you can ensure that your iris will bloom next year.
How to get a blooming iris? Find out below.
Why Won’t My Iris Bloom?
There are seven common reasons why irises don’t bloom. In no particular order, the reasons are:
- Lack of sunlight
- Water-retaining soil
- Wrong fertilizer
- Cutting the leaves off when deadheading
- Overcrowded irises
- Diseases and pests
Below, you’ll find the solution to every single one of these problems.
1. The More Sunlight, The Better
Irises love sunlight – they do best in full sun, although they can tolerate some shade. The best bloom, however, is achieved when you plant them in full sunlight – a sunlit iris is a blooming iris!
Ideally, your irises should get at least 6 hours of sunlight a day. The risk of sunburn is very low, and they can only benefit from getting more sun!
When you’re planting irises, it’s important to keep the soil free from weeds, and you can’t allow any other plants to block the sunlight. Iris rhizomes need plenty of sunlight for the plant to establish itself.
2. Use Well-Draining Soil To Avoid Root Rot
Getting the right soil mix is important because irises can easily develop root rot if they sit in wet soil. It’s important for the soil to drain well, which is one of the reasons why planting irises in containers is so popular.
When you plant irises in containers, the water can easily drain through the bottom. Water doesn’t drain as easily when you plant in the ground. If you’ve had water retaining issues in the soil before, add some compost to the soil to improve drainage.
If your irises aren’t blooming, the likeliest culprit is root rot, which is why well-draining soil is so important.
3. Water Your Iris Thoroughly, But Don’t Overwater
The relationship between irises and water is complex – they like to be watered regularly, but they don’t like it when the soil is soggy. It would be best to water them two or three times a week (provided that the soil is well-draining).
If there’s rain, you should water your irises less. The most important thing is to not overwater them – as explained before, irises are prone to root rot, which will kill the plant.
Since irises are drought-tolerant plants, you have plenty of leeway when it comes to watering! If you’re afraid you’re overwatering them, feel free to skip watering them for a week or so to see how the plant reacts.
The only time irises need plenty of water is during extremely dry and hot periods.
A few noteworthy varieties in this regard are the yellow iris, the Japanese iris, and the Louisiana iris. These varieties like wet soil and you can water them whenever you feel like it.
4. Fertilize With Low-Nitrogen Fertilizer
Fertilization is definitely necessary for irises – a 6-10-10 NPK fertilizer for flowering plants is a good choice.
You shouldn’t use nitrogen-rich fertilizer for irises because it promotes growth, and the plant will focus its energy on growing instead of focusing it on the bloom.
The best time to fertilize an iris is in early spring. Since they’re early bloomers, your irises will bloom quickly after the first fertilization.
Did you know that there are iris varieties that bloom twice, though? These varieties are called rebloomers.
If you have rebloomers, you should fertilize your irises again after the first blooming period ends – this will prepare them for the next blooming period.
5. Deadheading Is A Must For Blooming Irises
You should deadhead your irises as soon as the blooming period ends. All you have to do is cut off the flower stems all the way to the main stem. This doesn’t apply to leaves, though – you should leave them alone.
Irises need the leaves as they store energy for the winter. Even more importantly, irises need the energy to bloom – this energy is stored in the leaves.
To get a blooming iris, you need to keep the leaves intact (unless they’re infected with an illness or covered in pests).
6. Your Irises Aren’t Blooming Because Of Overcrowding
As it’s become clear by now, irises like to spend time in the sun and they drink plenty of water. When there are too many irises in a small area, none of them can get enough sunlight and water.
If this is the case with your irises, it’s very possible it’s the reason why they’re not blooming.
Irises are underground spreaders, so to say. Below the ground, there is a rhizome (also known as the bulb), which is the center of the iris’s body. Roots grow under the rhizomes, and the stem, flowers, and leaves grow above the ground.
Rhizomes will develop new rhizomes with time – it takes them at least three years to develop a new rhizome. Each new rhizome is a new iris, but this new iris will remain connected to the original iris.
If you don’t do anything about it, it’s possible for the original rhizome to develop not one, but two new rhizomes!
New rhizomes act as a second body that the original plant doesn’t want – this second body needs nutrients and sunshine just like the original plant, and lack of nutrients and sunshine can lead to both plants dying.
If there are too many irises in a single spot, diseases and pests can also easily spread.
Lack of sunshine, nutrients, water, and the easy spread of pests can lead to a bloomless season for your irises, which is why it’s crucial to divide them before it’s too late.
Wait until September to divide the rhizomes – at least 4 weeks need to pass after the final bloom. Simply dig up the iris with a trowel, shake all the dirt off from the bulbs and the roots, and gently rip off the new bulb (it should be able to come off as soon as you pull on it).
If it won’t let go, use a clean knife to cut it off! Now, you can plant the new bulb in the same spot (if there’s more than a single bulb, plant the second one in a different spot), while the old bulb should be thrown away.
7. Protect Your Irises From Pests & Illnesses
The most common iris pests are iris borers which, as the name suggests, really like to chew the insides of an iris to get to the rhizome. They need the nutrients to turn into moths.
No iris can defend itself from iris borers, but the Siberian iris is less prone to their invasions than other irises.
Borers can be killed with insecticides when their eggs are still hatching (iris leaves are usually less than 6 inches tall). A reapplication of the insecticide is needed about two weeks later.
You should also take out and burn all irises that have fallen victim to borers – you’ll see the brown leaves, and if you dig up the rhizomes, you’ll see the tunnels. This will prevent the borers from returning.
Aphids can also invade your irises, but they can be taken care of with weak pesticides!
When it comes to illnesses, root rot is a common one. The only way to prevent it is to keep an eye out for water and ensure you don’t overwater your irises.
Then, there’s also leaf spot, which results in small spots on the leaves – the best solution is just cutting the leaves off and burning them.
Irises Actually Bloom Easily – A Summary
If you think about it, getting irises to bloom isn’t that difficult. Plant them in a sunny spot, make sure that soil drains well, water them two or three times a week (less if it’s been raining), fertilize them once or twice a year, deadhead them once a year, make sure they’re disease-free, and divide them every 3-5 years.
Take care of these requirements, and there’s no way your irises won’t bloom!