The key to successful iris culture lies in understanding the growth cycle and thus the basic needs of this plant. Active growth in the South starts in earliest spring and becomes most rapid shortly before and during the time bloom stalks begin to emerge from the leaves. All the energy of the plant during this stage is concentrated on the production of leaves and flowers. Flower production is exhausting to the iris. After flowers fade, the plant takes a resting period that lasts a month or. During this resting period, the rhizome ripens. This ripening is important because the rhizome is a food storehouse, and it’s being in prime condition is essential to the continued health and life of the plant. As soon as the plant emerges from its annual rest, new roots begin to form, and tiny buds show on the mature rhizome. These new buds will produce next year’s flowers. Plant growth continues until late fall until heavy frost brings activity almost to a standstill.

Plant division should be made in the fall after the rhizome has ripened. Iris clumps may be dug, divided, and replanted, giving them about 6 weeks to allow new divisions to establish a root system before cold weather. September is a good month in North Central Texas for dividing iris. You should divide your iris clumps every 2-3 years or when flower production decreases.

The iris has a strict bloom order. After a rhizome blooms, it does not rebloom, but rather develops the buds that produces next years bloom. The iris is a heavy feeder and needs supplementary nutrients. The time to apply these nutrients is during the plants’ two periods of intense production: early spring around Valentines Day, and around the end of October or Halloween. A formula that best suits the iris is 6-10-10 or all purpose types. Use the recommended amount (from the package directions) sprinkled around –but not on- the plant. Water in thoroughly and then keep soil moist around the plant for a week or so to prevent a harmful concentration of the solution. Reblooming iris are also fertilized 4 weeks after bloom, using half the recommended amount, keeping the soil moist for about a week as done in early spring. Enjoy!