Irises will be distinctive in the garden, especially since they flourish in those wet regions where all other deep-rooted plants would suffer root rot. Better yet, since these plants retail in more than 300 different species you can pick from, there are colors with gorgeous petals to complement any garden.
As such, I understand how frustrating it can be if your irises have had their green stalks popping up from the ground but aren’t giving the colorful bloom you’ve been looking forward to for months. Here are five possible answers to your question “why aren’t my irises blooming?”
- The PH and/or Fertilizer is Wrong
- The Irises' Rhizomes May be Planted Too Deep or Too Shallow
- The Rhizomes Appear Lousy
- Sap-Sucking Pests Could be The Culprits
- Mulch. It Might Be Great, or Bad for Your Iris
- Spacing Your Irises is Essential
- There Isn't Sufficient Sunlight
- Irises Take Time To Establish Themselves
Why Aren’t My Irises Blooming?
If your irises are more than a year old and haven’t bloomed yet, here are several causes you can easily correct.
The PH and/or Fertilizer is Wrong
Irises aren’t fussy, but if the soil you’ve planted them on is too acidic or no phosphorous is present, your iris bed may be lacking the vigor it requires to get the plants to bloom.
Remember, irises prefer soil types similar to all other vegetables, i.e., slightly acidic but almost neutral. With that in mind, if you’ve never tested the soil before, do it and ensure it aligns with your irises’ needs.
Also worth noting, unlike lawn grass, irises do not require high nitrogen amounts. Compost manure will usually have the sufficient phosphorus the plant desires. If you ever need to add fertilizers, go for an all-purpose fertilizer with as much Phosphorus as Nitrogen and Potassium.
The Irises’ Rhizomes May be Planted Too Deep or Too Shallow
Regarding how you want the rhizomes planted, ensure they’re just underneath the ground’s surface so you can see some of them exposed in a few spots. That said, you do not want them exposed all through your irises bed.
If you planted the rhizomes too shallow, there is an easy fix. Simply cover them using well-rotted wood chips and an inch of compost.
Ensure you do not pile a thick layer of mulch, though, as it may cause the rhizomes to start rotting (mainly if the area doesn’t receive sufficient sunlight or the soil doesn’t drain.)
The Rhizomes Appear Lousy
An iris’ rhizome needs to be firm and slightly fatter than your thumbs. If you notice that your iris bed has a huge mixture of both, dig up the bed, separate the mushy rhizomes from the good ones, and replant accordingly.
That said, only do this in June or early August, as this is usually after the irises’ regular bloom period. Also, while digging up your irises, do not use a shovel. Use a spading fork as it’s less likely to cut or cause damage to the rhizomes.
Sap-Sucking Pests Could be The Culprits
As much as irises are astounding to nurture and look at, they tend to succumb to pest infestations and need extra nursing to flourish. In act, the pest you should be extremely wary of is critters with short antennas as these usually cause the most damage. They use their antennas to pierce into irises’ leaves to suck out the sap.
How does this affect your irises’ ability to bloom? Well, since irises usually require tons of energy to grow stronger, pests like critters deplete their nutrients, which in turn deprives them of their energy. And as every gardener knows, the less energy your plant has, the fewer flowers it will produce.
To manage this issue and prevent its adverse effects, regularly inspect your irises’ leaves and see if you can spot any insect damage. I suggest also using magnifying glasses to spot even the tiniest of insects.
Mulch. It Might Be Great, or Bad for Your Iris
On highly wet days, mulch tends to get saturated on your irises, moistening the plants and raising their humidity. This could end up rotting the irises.
That said, irises can also use mulch as a heat reflector. While this plant needs the sun, its rhizomes are usually sensitive to direct, scorching sunlight. Its leaves aren’t, though.
With that in mind, if excess mulch on wet days damages your irises, the plants will have no choice but to focus all their energy on healing. And as we just noted in the previous reason, any energy an iris plant dedicates to repairs eventually results in less energy devoted to blooming efforts.
Spacing Your Irises is Essential
Spacing is the most crucial component you’ll need to consider while planting your irises. Since these plants are usually planted in groups, not paying attention to the spacing could end up causing their rhizomes to crown one another out. This, in turn, reduces air circulation and becomes problematic.
There Isn’t Sufficient Sunlight
We’ve already established that irises love sunlight. Not direct sunlight, though. So, if the irises that aren’t blooming have been grown under a tree canopy that’s causing them to get stippled sunlight, this could be the issue. For irises to bloom, they need six to eight hours of sunlight every day.
Why so many hours? Well, because irises tend to use tons of energy, and if you do not train them to devote a good portion of their energy into flowering, they simply won’t.
Irises Take Time To Establish Themselves
Irises take time to settle into their homes, which can take up to eight months. In fact, it’s estimated that only a little over 40 percent of irises will bloom in the first year. The rest need more time to get their rhizomes established further into the ground first.
What’s more? The general rule of thumb is to plant your irises in early fall or toward the end of summer. This awards them the time they need to grow firm and be able to protect themselves from winter frosts by late fall.
Using the tips and tricks I’ve shared above, anyone should be able to troubleshoot, analyze, and get their irises to bloom again. What’s more? If you ever come across another plant parent also wondering, “why aren’t my irises blooming” do not hesitate to share these tips with them.