How to Get Irises to Bloom

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Irises (Iris spp.) come in a variety of sizes, shapes, flower colors and blooming season. If you have irises that are more than one year old and they are not blooming, there are a few possible causes which can usually be easily corrected, including allowing your irises more space to grow, giving them the sunshine they need, feeding them to help them bloom.

Method 1
Method 1 of 3:

Giving Your Irises Space

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    The first and most likely cause for irises failing to bloom is overcrowding. Irises must be dug up, divided and replanted every three to four years. [1]
    • If this does not happen, it becomes less likely that your irises will bloom.
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    Use a shovel to begin working the soil roughly six to eight inches away from the stems of the irises. Loosen the clump of iris roots away from the dirt.
    • When it is loosened up, lift the clump out of the ground with the tip of the shovel.
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    Pull multiple rhizomes apart by hand. Make sure there is a healthy fan of leaves attached to each rhizome.
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    Re-plant the remaining, healthy rhizomes right away. Choose a spot that is bright and sunny. The soil should drain quickly or else your irises will get soggy feet, which can also halt their ability to bloom. [2]
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Method 2
Method 2 of 3:

Giving Your Irises Sunshine and Water

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    A lack of sunlight will prevent irises from blooming to their full potential. These plants require at least four to six hours of direct sunlight each day. [3]
    • Most varieties prefer six to eight hours of sunlight.
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    If your irises are planted in a shady place, move them to a sunnier location in late summer. Make sure the soil at the new location drains quickly. [4]
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    Sufficient moisture is necessary to get irises to bloom but irrigation frequency depends primarily on the iris species.
    • Reticulated irises (Iris reticulata), for example, should be watered once per week or so if it does not rain in the spring but only once every few weeks throughout the summer months.
    • German irises (Iris germanica) should be watered when the top of the soil begins to dry out. This should be done throughout the growing season.
    • Southern blue flag irises (Iris virginica) require constantly moist soil and actually thrive in sandy-bottom bogs.
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    Adjust the watering schedule according to your specific iris's needs.
    • Always water irises in the morning so that the moisture will be available to them during the heat of the day.
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Method 3
Method 3 of 3:

Feeding Your Irises

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    High-nitrogen fertilizers like those used to fertilize grass encourage only green leafy growth. [5] They do not encourage flowering.
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    This means that the fertilizer should contain 5% nitrogen, 10% phosphate, and 10% potash. [6] Plan to use about ¼ pound of fertilizer per 25 square feet.
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    Instead, sprinkle the fertilizer around the outside of the main clump of rhizomes. Water the plant to help mix it into the soil.
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    A 6-month slow-release formula can be used if preferred. If a slow-release formula fertilizer is not used, reblooming irises should be fed fertilizer again immediately after they bloom in the spring.
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  • Question
    Do irises bloom more than once a year?
    Ninox
    Top Answerer
    They only bloom once a year, but the blooming can be very long for some species.
    Thanks! We're glad this was helpful.
    Thank you for your feedback.
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  • Question
    Can I make irises bloom earlier? We have a show in 2 days, and I need them to bloom.
    Ninox
    Top Answerer
    No, flowers appears if the temperature is high enough during some days, but nothing can accelerate the process.
    Thanks! We're glad this was helpful.
    Thank you for your feedback.
    If wikiHow has helped you, please consider a small contribution to support us in helping more readers like you. We’re committed to providing the world with free how-to resources, and even $1 helps us in our mission. Support wikiHow
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  • Question
    My irises were blooming less a few years ago. I dug them up and divided them. They grow wonderfully, but no blooms! In the past 3 years, only a few have had a bloom; they multiply, but no blooms. Any ideas?
    Ninox
    Top Answerer
    Remove the rhizomes from the ground and cut 2/3 of the leaves. Add fertilizer, then replant the rhizomes.
    Thanks! We're glad this was helpful.
    Thank you for your feedback.
    If wikiHow has helped you, please consider a small contribution to support us in helping more readers like you. We’re committed to providing the world with free how-to resources, and even $1 helps us in our mission. Support wikiHow
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      References

      1. ↑ Clark Hill. Plant Specialist & VP of Operations, Platt Hill Nursery.
      2. ↑ Clark Hill. Plant Specialist & VP of Operations, Platt Hill Nursery.
      3. ↑ http://www.clemson.edu/extension/hgic/plants/landscape/flowers/hgic1167.html
      4. ↑ Clark Hill. Plant Specialist & VP of Operations, Platt Hill Nursery.
      5. ↑ Clark Hill. Plant Specialist & VP of Operations, Platt Hill Nursery.
      6. ↑ http://www.ncagr.gov/cyber/kidswrld/plant/label.htm

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