Daylilies, one of the most commonly divided of all perennials, spreads with enthusiasm to form dense clumps. Although they keep blooming even when crowded, you'll have even more of a wonderful thing after you've divided them. The best time to work on daylilies is in the early fall, after the bloom has ended but before any serious frost. Before digging up any plants, prepare the holes they will go into ahead of time, adding whatever is necessary to the soil. Large clumps of daylilies can be divided right in the ground. Plan your cuts so that each division will include one to three foliage fans and the root tissue below. Drive a sharp spade down firmly between the fans, cutting through the roots. Then dig under and around the sections and lift them away from the sides of the main clump. Cut about half the fan off to reduce moisture loss, and get them planted quickly into the holes you prepared ahead of time. Be sure to keep the ground moist while they adjust to their new spot by mulching and watering frequently. Iris can also be divided with great results. You can tell when they need to be divided because they just don’t bloom like they used to, and roots push to the surface where they can be seen. You have to be gentle with iris. Loosen the soil thoroughly around the plants with a garden fork or a shovel, taking care not to break tender feeder roots. Carefully lift the plants out of the ground. Shake or rinse the soil off to inspect for damage. Separate the roots, starting with those that split into sections naturally in your hand. Cut others apart with a sharp, clean knife, separating v-shaped pieces and preserving the feeder roots. Trim the foliage fans to about four inches long to reduce moisture loss while they adjust. Set the roots on mounds in the middle of holes you have already prepared with the feeder roots spread over the mound. The top of the root should just peek out at ground level. Press two to four inches of soil firmly over the roots and water the area well, putting mulch around it to preserve the moisture. Both daylilies and iris are very hardy and will bounce back from division with exuberance, rewarding you with ever increasing beauty.