No, you do not need to soak iris bulbs before planting. If they already have rhizomes, however, soaking can help loosen them up, making them easier to work with and easier to plant into the ground.
Bearded irises (Iris germanica ... inches and do not compost but trash. Remove any dead or diseased foliage, spent flowers, weeds, and any fallen leaves. Bearded irises grow from rhizomes.
After the flowers dry up do not cut down the ... irises are deer and drought resistant. (Rhizome rot is a risk if the soil is kept wet.) Grow your own Bearded Iris. You might just end up sharing ...