Why are my iris not blooming

If there’s one thing that all plants in the Iris (EYE-ris) genus are known for, it’s their spectacular blooms.

These plants are generally considered to be easy to care for and will continue to bloom for many years when cared for, but sometimes, things can go wrong, and your iris will fail to bloom.

Here are the many reasons this can happen and what to do about it.

Why is My Iris not Blooming?

There are three significant factors in an iris failing to bloom: age, health, and proper care.

When any of these go wrong, it can fail to bloom.

Age

An iris can live for quite a few years, so it takes time to mature.

For example, an iris planted from seeds won’t bloom until its second year.

Likewise, an iris can grow past its prime.

The Siberian iris is a prime example of what can happen when a plant grows too old.

These plants will eventually form a ring of healthy rhizomes while the older central rhizome slowly dies out and may be replaced by weeds.

It’s a clear sign that it’s time to divide the plant, discarding the older rhizome and replanting the younger sections.

Improper Watering

Watering an iris properly is essential, as too much or too little can lead to problems.

Too much water will lead to root rot and fungal disease, harming or even killing your iris plants.

In such cases, you may have to dig up the plant, remove diseased portions, and plant it in fresh soil.

Depending on your iris, the plant will generally need to be watered when the soil feels dry, approximately+ 1” to 2″ inches deep.

Not enough water can stress the plant out, resulting in it failing to bloom, so using the soak-and-dry method is an excellent way to ensure the plant is getting just the right amount every time.

Inadequate Light

Irises love the light and will fail to bloom if they’re not getting at least 6 hours of full sun per day.

In places where the midday sun is too harsh, this exposure can be in the morning or evening.

You can tell if your iris is getting enough light simply by checking it every hour on a sunny day to see when it ends up in the shade and when it’s getting full sun.

Infestation or Infection

Overwatering and exposure to sick plants can cause your iris to become infected or infested.

It’s not uncommon for an infestation to happen due to a fungal infection, such as the case with fungal gnats.

Likewise, piercing insects produce honeydew, which can attract some forms of fungus.

Because both of these problems can cause the plant stress and drain its resources, they may prevent the plant from blooming.

Practicing proper care techniques and occasionally checking for signs of an infestation or infection is often enough to ensure your irises never get too sick to produce blooms.

Malnutrition

As with all things, your iris needs its nutrients in moderation.

Too much nitrogen or not enough phosphorus will make the plant focus on foliage rather than flowers.

Additionally, your plant will fare best in slightly acidic soil.

When in doubt, perform a soil test to see if you need to adjust the fertilizer you’re using or augment with organic compost.

Giving your Iris some bone meal in the early spring will also help encourage healthier blooms.

Overcrowding

Overcrowding is a problem that becomes more common as your iris ages.

When the clumps get too big, the individual rhizomes will compete for resources, causing the entire chunk to suffer.

For this reason, it’s best to divide your irises every couple of years, even if you aren’t trying to propagate them.

Planting Depth

There are several critical differences between iris rhizomes and iris bulbs that are easy to overlook. Many insist the two are the same thing.

However, cutting open a rhizome will look like potatoes or other tubers; it will layer bulbs much like an onion.

More importantly, bulbs and rhizomes need to be planted at different depths, or they may fail to bloom.

As a general rule, a rhizome should be planted so that the top third is above ground.

Bulbs should be planted three times as deep as their size (i.e., a 2″ inch bulb should be planted in a hole 6″ inches deep).

Keep in mind that adding mulch or compost over an iris will affect the depth of the bulb or rhizome, and it should be avoided.

Rhizome Health

Finally, the health of your bulb or rhizome can affect the plant’s ability to bloom.

Check the root system for soft spots or a foul smell when dividing or transplanting.

Discoloration or odd shape may also be signs of a sick tuber.

In many cases, you can safely cut away the diseased sections until only healthy tissue remains, saving the plant.

However, sometimes the damage is so extensive you’ll have to discard the whole plant and start over.

By SF Gate Contributor Updated September 25, 2020

Scientists classify the more than 300 species of iris (Iris spp.) into two groups: those that grow from rhizomes and those that grow from bulbs. One factor that plants in both classes have in common is that all of their flowers have six petals. Other than that, the diversity within the genus is striking.

The U.S. Department of Agriculture (USDA) plant hardiness zones in which irises are hardy vary by species and cultivar. Bearded iris (Iris germanica) is hardy in USDA zones 3 through 10, reports the Old Farmer's Almanac. Any kind of iris may have problems blooming if it isn't given proper conditions or care.

An iris that won't bloom may be planted in too much shade, be either too wet or too dry or planted too deeply. In addition, ensure that you use a fertilizer that is not too high in nitrogen.

Although an iris will grow in shade, it will produce few or no flowers there. It needs lots of sunshine to bloom, according to Missouri Botanical Garden. Plant your iris in the sunniest part of your garden, and ensure tree branches won’t shade the plant and that other surrounding vegetation is too far to cast shadows on the iris. Some iris species, however, do fine with one-half day of sunlight.

Iris is considered drought-tolerant. When under stress from a lack of water, however, the first element sacrificed is flowering. Even the most prolific iris will fail to bloom if it doesn’t receive adequate moisture.

A rule of thumb is to water an iris slowly when the top 2 inches of its soil is dry. Too much moisture is as devastating as not enough moisture, however, causing rot and, especially in bearded iris, leaf spot diseases, according to the Monterey Bay Iris Society.

If you bury an iris rhizome too deeply, it will repay you by not blooming or, even worse, by rotting. The key to success when planting the rhizome is to allow the top of it to remain exposed. That arrangement allows air to circulate around the rhizome, and sunlight will ensure it doesn’t remain too moist. Those are perfect conditions for blooming to occur.

Iris, like many flowering plants, fails to bloom when too much nitrogen is in its soil. Because the plant requires sufficient phosphorous, however, fertilizing it is a delicate balancing act. A soil test can help you determine which nutrients are missing in the soil and the best way to achieve a balance of nutrients.

A rule of thumb is to provide one iris' soil with 1/2 cup of 5-10-10 fertilizer in spring before the plant blooms and once again immediately after it blooms; don't put fertilizer on an iris' rhizomes but around the rhizomes instead. An option to encourage a reluctant bloomer is to use 10-55-10 fertilizer for the spring application.

If your iris suddenly ceased to bloom after years of being grown in the same spot, then it may be overcrowded. Remedy that situation by digging up the rhizome or bulb and dividing it.

Dividing is easier if you trim the iris' foliage to about 6 inches in height, shake the soil off the clump and use your fingers gently to break the young bulbs or rhizomes from the main tuber. Replant the resulting new irises immediately, and keep their soil moist as they become established.

Are your Irises are not blooming this year yet? It can be disappointing when you get little to no blooms.

Irises are considered hardy perennial flowers that can grow as long as their basic needs are met.

Here are some of the issues I have seen in my irises.

Why Are My Irises Not Blooming?

Irises may not bloom for a few reasons including issues with shade, water, space, nutrition. The most common issue with irises blooming is how deep the bulb or rhizomes is planted. If the bulb is planted too deep the iris will sprout greenery but will not show any blooms. An iris can also bloom one year and not bloom the next. This can be due to the problems listed or the type of plant.

5 Reasons Why Irises Aren’t Blooming

There are five reasons an iris may not bloom.

Not enough sunlight
Over or underwatering
Planted too deep
Not enough space
Poor soil nutrition

While these are the most common issues to occur with irises, another issue I have seen is in the plant itself.

An iris will often need a year to establish roots before you see any blooms. If you have recently planted your iris, give it another year to establish itself.

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.

It is best to make sure all the common issues below are not affecting your irises before testing for fungi or insects.

Too Much Shade

An iris will grow in a shaded area, but it will produce little to no blooms.

Irises need 6 hours of direct sun each day to bloom. Full sun is especially important for reblooming species.

Make sure your iris is not covered by other plants or trees and that the entire plant is exposed to the sun.

Too Much or Not Enough Water

Irises need well-draining soil to create their blooms. The plant is drought resistant.

It is best to water well at the beginning of the season to ensure the roots of your new iris take.

If the bulb or rhizomes are mushy or soft you will not see any flowers even though the iris may still grow greenery.

Planted Too Deep

The iris rhizomes and bulbs need lots of air and sunlight to grow.

I have found that planting iris rhizomes so that they are poking out above the soil creates the best results.

If your iris is too deep you can see some growth, but your blooms will be limited.

Not Enough Space

Rhizomes multiply as the iris grows. Your iris bulbs should be about 12 to 24 inches apart.

They will commonly overcrowd themselves within two to four years of growth.

I usually dig up and split the rhizomes every few years to increase the space the iris has to grow. This will increase bloom production.

You may want to move your iris if the area your iris is growing in is dense with other fast-growing plants.

Your iris needs room to grow. Weeds and other plants can start to choke out the iris roots.

Poor Soil Nutrition

The final issue you may run into is poor soil nutrition. You can get a soil tester from any hardware store. Check the nitrogen and pH of your soil.

The PH should be 6.8 to get the best blooms. Make sure your soil is set up properly to feed your plants.

Fertilize irises in early summer if your soil needs extra nutrients. Your iris should not need constant fertilization unless your soil is low in nutrients.

Weather Conditions For Your Iris

There is a chance that a late freeze in your area caused your bulbs to freeze or become dormant.

I plant my iris bulbs or rhizomes in late July to September to give the bulb time to grow roots.

If the freeze happens before the bulb is established then the iris may go dormant for the year. Allow your iris time to establish itself before giving up on it.

Frequently Asked Questions About Why Are My Irises Not Blooming

What is The Best Fertilizer For Irises?

The best fertilizer for your irises is a low nitrogen fertilizer at a 5-10-10 split. Most common garden fertilizers will work. You can also use bone meal as a fertilizer on irises. I place the fertilizer around the bulb or rhizome, not on it. It is best to fertilize your plants a month before you expect them to start blooming.

How to Get Irises to Rebloom?

To help improve your iris blooms, start by pruning your irises to help them rebloom in the same year. Then, make sure your fertilizer offers the right nutrients. Lastly, watch out for weeds. For a better-looking garden, I mix and match iris species to increase the length of time the garden blooms. The Bearded iris blooms early in the year while the Siberian iris blooms later. Mixing these species will give your garden a mix of beautiful blooms throughout the year

How Long Do Irises Bloom?

An iris will bloom for about two weeks each year. Many iris variations will rebloom throughout the year. Some variations will only bloom every second year. Pick a mix of iris species to help your garden look full all year long.