Bearded Iris (Rebloomers) Planting Guide

Sooner is Better
Bearded iris grow from rhizomes, not traditional tulip-like bulbs. Iris rhizomes are fleshy tubers that are planted on their sides close to the soil surface. Roots grow from the bottom side of the rhizome anchoring the plant and accessing nutrients and moisture from the soil. These roots need to establish before winter's cold descends on the garden. In freezing climates, late summer through early fall planting is an ideal planting time. In warmer areas, bearded irises may be planted through late October and early November. Late planted rhizomes may not bloom full strength their first spring, but catch up and produce normal flowering displays thereafter.
PLANTING
DEPTH

top 1/3 of rhizome exposed above soil line

WATER
QUANTITY

light - quite drought tolerant once established

SUNLIGHT
QUANTITY

Full sun to light shade, bright light indoors

PLANTING
PROXIMITY

6-12" Inches Between Planting

Outdoor Beds
  1. Find a location where the soil drains well. If there are still water puddles 5-6 hours after a hard rain, scout out another site. Or amend the soil with the addition of organic material to raise the level 2-3" to improve the drainage. Peat moss, compost, ground bark or decomposed manure all work well and are widely available. Iris must not sit in soggy soil or the rhizomes will rot.
  2. Site your iris where they will receive full sun. In the hottest parts of the country a bit of afternoon shade is fine.
  3. Space rhizomes 8-12" apart. Position them so the end with the existing leaves points in the direction you want the initial growth to occur. Many people place the rhizomes facing towards the front of a bed or border, for instance. Plant the rhizomes horizontally, so the tops are just peeking above the soil surface and the roots are spread out in the soil below. Compared with most bulbs, this seems too shallow, but for bearded iris it's perfect. In very hot areas, cover the rhizome with 1/2”-1” of soil to prevent the rhizome from sustaining sun damage.
  4. After planting, water well, gently soaking the soil and settling it around the rhizome. Then ease off on the water; your bulb doesn't need moisture when there isn't yet growth to support. Foliage will begin to form in the autumn. In warmer climates, a few varieties may even bloom in the winter. For most areas, spring will bring a flush of new foliage and flowers.
  5. When in bloom, feel free to cut iris flowers for beautiful, often lightly fragrant bouquets. While iris stems often aren't long lasting cuts the flower colors and detail are outstanding when appreciated up close. So cut a few!
  6. Water bearded iris regularly until about 6 weeks after the flowers have faded. This moisture will increase clump development and bud production for the next blooming period. A little moderate-nitrogen fertilizer (6-10-10, for instance) applied in early spring and after flowering will help the plants produce lots of flowers. On the other hand, high nitrogen fertilizer will encourage rot. This is one case where more is not better.
  7. After blooming has finished for the season, feel free to cut off the spent flower stems but leave the foliage in place. The sword-like leaves will gather sunlight, photosynthesize and provide nourishment for next season's show. The leaves will also provide a strong linear element in your garden. Water as needed during active growth periods.
Pots, Barrels, Tubs & Urns
  1. Bearded iris grow into large, perennial plants with rhizomes that expand into a large network over time. Keep this in mind as you choose a container and select one that is 2 gallons or larger. 
  2. Fill your containers with good quality, well-drained soil. Almost any commercially available potting medium will work fine. Make sure there are adequate drainage holes; the iris rhizomes must never sit in waterlogged soil or they will rot.
  3. Site your iris where they will receive full sun. In the hottest parts of the country a bit of afternoon shade is fine.
  4. Space rhizomes 6-8" apart. Position them so the end with the existing leaves points in the direction you want the initial growth to occur. Place the rhizomes facing towards a gate through which visitors will ender your garden, for instance. Plant the rhizomes horizontally, so the tops are just peeking above the soil surface and the roots are spread out in the soil below. Compared with most bulbs, this seems too shallow, but for bearded iris it's perfect. In very hot areas, cover the rhizome with 1/2”-1” of soil to prevent the rhizome from sustaining sun damage. Tuck them in so that the top inch of the bulb is left above the soil surface. The top of the bulb is the part that looks a little like the stem area of an onion and the bottom has a flat plate, often with a few roots attached.
  5. Water well, gently soaking the soil and settling it around the rhizomes. Until new growth shows that the plants have begun to root in, water only lightly.  Less is usually better at this stage.
  6. Enjoy your flowering irises and feel free to snip a stem here or there for use in a vase. This won't hurt your plants.
  7. After blooming has finished for the season, feel free to cut off the spent flower stems but leave the foliage in place. The sword-like leaves will gather sunlight, photosynthesize and provide nourishment for next season's show. The leaves will also provide a strong linear element in your containers. Water as needed during active growth periods. Water needs are typically 1/2-1" of moisture per week, or more if the iris are in pots with porous sides, like terra cotta.