Bearded Iris Planting and Culture Guide
Preparing your planting area
Bearded irises require excellent drainage (raised beds are ideal) and at least a half day of sun. They will perform best in friable soil that is neither too sandy nor too clayey. Alfalfa meal or pellets, humus, and compost make excellent amendments in any soil. Chemical fertilizers, if necessary, should be incorporated into the soil several weeks before planting. Avoid high-nitrogen amendments such as manure and nitrogen fertilizers, as excessive nitrogen can cause problems in bearded irises. Any soil pH from moderately acidic to moderately alkaline will suit bearded irises. They are adaptable plants and will grow in less-than-ideal conditions, but the better you treat them, the better they will perform for you!
Planting your iris(es)
Remove any leaves that may have yellowed or died. New leaves will grow once the plant has settled in. If your temps are very hot – in excess of 90 degrees – you might consider putting your irises and keeping them under a shady tree until temps cool down a bit. Be certain, however, to get your irises planted into the garden at least 6 weeks before your first frost to allow ample time for rooting in.
If your temps are reasonable, go ahead and plant right away. Dig a hole deep enough for the roots to spread downward, and create a small knoll of dirt in the center of the hole. Place the rhizome on the knoll with the roots spreading downward around the sides. Fill in the hole around the roots and rhizome, and firm the soil. Iris should be planted so that the roots are fully underground and the top of the rhizome is level with or slightly below the soil surface. If you garden in a climate that is either excessively hot or severely cold, it may be advisable to cover the rhizome with up to 1/2″ of light soil or sand to help protect the rhizome from direct exposure to extreme temps. If the rhizome is planted too deeply, the plant may grow but refuse to flower. If you choose to mulch your garden, take care to keep the mulch pushed away from the rhizomes so the surrounding soil does not retain too much moisture. I prefer to plant miniature and standard dwarfs at 1′ spacing and the taller medians and talls at 2′ so I don’t have to divide every other year.
Water the newly planted iris well, then water again deeply once a week for a couple more weeks if rainfall is insufficient. Overwatering may cause bearded irises to rot, so allow soil to dry out between waterings. Drip irrigation with soaker hoses is preferable to overhead watering. Once your iris has rooted in and starts to grow new foliage, it is no longer necessary to provide supplemental water except in very arid locations.
Then what?
Keep your irises weeded as necessary and don’t allow other plants to crowd them. Remove any dead, dying, and diseased leaves from your irises and discard them in the trash. Next spring you may have some bloom, but your best bloom will come on 2-3 yr old clumps. A light feeding of bone meal or superphosphate 4-6 weeks before bloom will promote best performance. Divide clumps when they appear overcrowded and you notice a diminishment in bloom. Miniature and standard dwarfs tend to be very vigorous growers and may require division every 2-4 years, depending on your growing conditions. Taller medians and talls typically grow at a more modest rate and may require division every 3-5 years.
Special note about arilbreds
Arilbreds can generally be grown just like any other bearded iris, but they may acclimate to your conditions more easily if you plant them 1/2-1″ deep in lean, dry, sandy soil. Water once immediately after planting, then do not supply any additional supplemental water.
Happy Planting and Enjoy Your Irises!