STEP 1: Dig the entire clump gently out of the ground with a spading fork or shovel.
STEP 2: Wash soil from the roots. Trim the healthy leaves into fan shapes about 6” in overall length. Remove poor leaves and old bloomstalks. Don’t compost diseased materials—destroy.
STEP 3: Cut off the outer rhizomes. Discard the old center portion without leaves. Cut out any signs of rot and dust with fungicide as a precaution.
STEP 4: Plant each division as shown by pressing the rhizome into a mound in the planting hole, with the top soil of the rhizome almost at soil level. Fill in and firm the soil.
HOW TO GROW IRIS -----Culture of Bearded Iris
Bearded Iris are about the easiest of garden plants to grow and will give good results with a minimum of care, but like all plants, the better the culture the more magnificent the display.
Iris need good drainage and plenty of sun. Select a site that gets a least 6 hours of sun each day. Iris may survive, but will not bloom if grown with too much shade. Also, be careful that neighboring plants don’t grow across the top of the rhizome if you are planting the Iris in with other plants. Sunlight and air right down to the rhizome are necessary if you want to avoid rot.
Any good garden soil will grow Iris. If you have problems growing other plants, perhaps it would be best to have your soil tested and/or to seek the advice of a local nurseryman before trying Iris. However, in general the following is true. Any soils should be built up with the addition of plenty of compost. Agricultural gypsum (if soil is alkaline) or agricultural lime (if soil is acid) can be used to help “loosen” heavy clay soils, and there again, compost is beneficial. A balanced chemical fertilizer, if needed, may also be dug in at planting time. Use the type of fertilizer that you would for tomatoes or vegetables — one somewhat higher in phosphorous and lower in nitrogen — rather than the type used for lawns (unless, of course your soil is deficient in nitrogen). A high nitrogen content promotes too lush growth which is more susceptible to rot, while the phosphorus promotes strong roots, solid rhizomes and strong bloom stalks. Be sure to mix in all soil amendments thoroughly — that way the plant’s roots, as they grow, are constantly in contact with some of the good stuff you’ve added.
The best time to plant Iris is during their semi-dormant period which extends from a few weeks after blooming until new growth begins in the fall (July, August, and September in our area). Plant the rhizomes with the top just below the surface of the soil. If you are dividing old clumps (this is necessary every couple of years) or buying new plants, select rhizomes to plant with a good fan of leaves and evidence of increase. Beware of rhizomes that show evidence of rot or that are mushy or soft at the base of the fan where the leaves join the rhizome.
Soak the ground after planting and then allow the soil around the top of the rhizome to become dry before watering again. Once the Iris are established water deeply but infrequently.
Remember that too much water is more likely to be a problem than the lack of it since summer heat and too much moisture can cause rot. If rot does occur, scrape out the infected area until healthy tissue (white color) is reached and expose to the air and sunlight.
Some people then give the wound a light dusting of soil sulfur, dilute chlorine bleach (one part bleach, ten parts water) or gypsum as added insurance.