Blue Iris Iris spuria

Blue Iris (also commonly known as Salt Marsh Iris or Butterfly Iris) is a 5-foot tall, beardless, herbaceous perennial bulb native to Europe, Africa, and Asia. It is one of the tallest of the iris family. It typically grows in clumps with attractive 4 foot long leaves and flowers that display a range of colors from bluish-purple white, blue, purple, wine and brown. The genus is named for the Greek goddess of the rainbow and the epithet, Spuria, means false.

Blue Iris grows best in rich, well-composted, medium moisture, neutral to slightly alkaline, well-drained soils. For best flowering and disease resistance site the plant in full sun, although they will tolerate light shade. Provide consistent moisture during growth periods, but avoid wet soils. Many spurias are summer dormant and need less moisture after bloom (that is, plant growth often stops during hot weather and plants can survive with little watering). Amend heavy clay soils prior to planting (for example, add coarse sand or organic matter). Raised plantings are another solution. Avoid overhead watering. Deadhead individual spent flowers and remove flowering stems to the ground after bloom. Divide plants immediately after flowering when overcrowding occurs. Keep in mind that the most frequent causes of failure to flower or sparse flowering are rhizomes planted too deep, too much shade, too much fertilizer or plants that are overcrowded and need division.

Diseases, Insect Pests, and Other Plant Problems: Good soil drainage is essential to combat potential soft rot problems. You should avoid the use of mulch for the same reason. Insect problems include iris borer, iris weevil, slugs, snails, thrips, whiteflies and verbena bud moth. Major disease problems include bacterial soft rot, crown rot fungus, rhizome rot, and fungal leaf spot. Watch for mottling of leaves and flowers which may indicate the presence of mosaic virus. Mustard seed fungus can be fatal. Good sanitation practices can often prevent problems.