Growing Irises:
How to Grow Iris Plants Organically

Growing irises produces flamboyant flowers that will add more than a touch of intrigue to your garden... after all, it's no accident that the iris plants’ beauty has caught the imagination of master painters such as Van Gogh, Monet and Georgia O’Keefe.

Dividing plants every three or four years ensures your irises won’t lose the glamour of their first few years.

Growing Irises: Plant Snapshot

Growing Irises
  • Iris (Iris)
  • Annual or perennial? Perennial
  • Recommended varieties (by color):
    • Blue: Iris verna, Manhattan Blue, aucheri ‘Austrian Sky’, histrioides ‘Major’
      Lavender: Iris germanica ‘Earl of Essex’
    • Orange: Ruthenica
    • Peach: pseudacorus
    • Purple: Iris ensata, Iris Germanic ‘Batik’, Chrysographes, Ensata, Dark Vader, 'Bearded Iris'
    • Red: Red at Night
    • Yellow: ‘Baby Blessed’, ‘Sarah Taylor’, Pseudacorus, Beechfield
    • White: Iris ‘Bright White’
  • Recommended USDA Hardiness zones: 03a to 10a
  • Mature Height: 2 to 60 inches (5 to 150 cm) depending on variety
  • Mature Spread: 2 to 18 inches (5 to 45 cm) depending on variety
  • Sun Requirements: Partial shade to full sun
  • Blooming season: Late Spring, Early Mid & Late Summer
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Growing Irises: Planting Iris Bulbs & Seeds, Transplanting Irises and/or Dividing Irises

Where to Find Planting Supplies...

The following resources offer effective, healthy and/or well-rounded options. Click the links to go there now...

Iris seeds can be sown at any time over the colder months in fall, winter or very early spring. Soak seeds for between two days and two weeks, then put them into iris containers filled with sieved garden compost or a nutrient-rich seed starting mix.

Put pots into a cold frame or sheltered place outdoors to keep them moist. Transplanting iris plants into your garden should be done during the second year of growth.

See the snapshot box below for information about dividing irises.

Snapshot: Planting Irises

  • Germination soil temperature: 40 degrees F (5 C)
  • Distance between plants: about 10 inches (25 cm)
  • Planting depth: roots in soil, but rhizome on surface
  • Days to germination: 3 to 4 months
  • Preferred soil pH (see soil pH tester for more information): 6 to 7
  • Root division information (perennials only):
    • Root system type (clumping, spreading, rhizome or tuber): rhizomes
    • Roots division frequency: Every 3 to 4 years
    • In which season should dividing occur? Late summer and early fall
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Growing Irises: Iris Plant Care

Where to Find Growing & Plant Care Supplies...

For effectice, healthy and/or well-rounded options, click the following links...

Standard flower watering guidelines apply. Plants should not need staking, although newly planted divisions should always be trimmed to prevent wind rock before the roots are established.

Cut back irises in late fall after flowering has finished. If the plant has already succumbed to frost damage, it’s still worth removing excess foliage to prevent it from providing shelter for pests and diseases.

Avoid using farmyard manure to improve soil as this should not come into contact with rhizomes. Instead, use a slow release fertilizer like organic poultry manure pellets in spring and late summer.

Snapshot: Iris Plant Care

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Growing Irises: Harvesting/Cutting Time

Dutch hybrid irises are often grown as cut flowers. Create an out of sight section of your garden for growing cut flowers so that you don’t undermine your flower borders by stealing plants for indoors.

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Growing Irises: Pests & Diseases

Keep the base of your iris plants free from debris to improve garden hygiene. If you notice rot or mold damage on your iris plants, remove that part of the clump by digging it up and destroying it.

The following pests and diseases have been known to affect the success of growing Irises (see Organic Garden Pest Control for information about how to prevent and address pests and diseases)...

Pests

  • Aphids
  • Carrot Beetle
  • Foliage-feeding caterpillars
  • Hoplia Beetle
  • Lesser bulb flies
  • Snails and slugs
  • Spider mites
  • Thrips
  • Whiteflies

Diseases

  • Bacterial soft rot
  • Gray mold
  • Leaf spots
  • Root and crown rots
  • Rust
  • Viruses
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