Daylilies and irises are perennial flowers that after a few years will get crowded and need dividing. You may notice a decline in the size of the flowers and shoots, or the center of the clump becomes empty. How long it takes for the area to get crowded depends upon the cultivar. Older cultivars of both flowers are more vigorous growers and need to be divided sooner than the newer hybrids. Dividing the daylilies and irises is an inexpensive way to increase your garden area or grow more cutting flowers for indoor arrangements.
Divide daylilies in the spring if you live in USDA planting zones 3 and 4; fall if you live in zones 9 and 10. All zones in between can divide at either time but at least six weeks before the first freeze date.
Dig up the entire clump with extra soil around it so as not to damage any of the roots. Remove any dead leaves and stems from the clump. Using a gentle stream of water from the garden hose, rinse off as much soil from the clump as possible.
Cut back foliage to 6 inches and cut leaves in half. Cut between each set of fans and its roots or you can keep a group of fans and their roots together for a fuller plant.
Amend the garden soil with a few handfuls of compost and a slow-release fertilizer while the daylilies are out. Refer to manufacturer’s suggestions as to amount of fertilizer to apply.
Plant the daylilies back in the garden bed with the crown 1 inch deep and 12 inches apart. Water the daylilies well immediately after plantings.
Cover with a 2-inch layer of mulch to help retain water and protect the roots through the winter.
Divide irises in July or August, every three to four years. You will notice the flowers are crowded and are not growing as well when they need to be divided.
Dig out the entire clump of rhizome and some soil around it so you don’t damage the roots. Rinse off as much soil as possible with a gentle stream of water from your garden hose.
Cut through the rhizome so that each section has a leaf attached and some roots at the bottom of the rhizome. Trim any remaining leaves by cutting at least one-third off. Discard any old woody sections that have no roots as they will not rebloom.
Amend the soil with a few handfuls of compost. Use a slow-release fertilizer if the irises are the reblooming type.
Plant the sections back in the flower bed by mounding the soil and draping the rhizome over the mound, leaving the top of the rhizome exposed and covering the roots with soil. Hand tamp the soil down tightly and water the plants well.