Pruning is a maintenance technique that directly influences the health and appearance of the iris plant, particularly the widely grown bearded iris. This perennial grows from a thick underground stem known as a rhizome, which stores energy for the following season’s growth and bloom. Pruning ensures that the iris directs its energy efficiently, preventing disease spread and encouraging robust flowering. By understanding the specific timing and methods for cutting back spent blooms and aging foliage, a gardener can significantly improve the plant’s long-term vigor.
Removing Spent Flower Stalks
The process of removing faded flowers, deadheading, is the first pruning task of the growing season. This action is performed to prevent the plant from developing seed pods after the bloom cycle is complete. Seed production requires energy that would otherwise be used to strengthen the rhizome for next year’s blooms. Redirecting this energy is particularly beneficial for reblooming varieties of bearded iris, which may produce a second flush of flowers later in the year.
To deadhead correctly, wait until the individual flower has fully withered, including the swollen green sheath behind the petals where the seed will form. On a stalk that has multiple buds, only pinch or snip off the individual spent flower head to allow any remaining buds to open. Once all the flowers on a single stalk have finished blooming, the entire stalk should be removed to prevent decay. Trace the stem back to the base of the plant, cutting it off cleanly near the ground, about one inch above the rhizome. Making an angled cut is recommended, as it encourages water runoff and helps to reduce the risk of moisture-related diseases.
Cutting Back Foliage for Dormancy
A seasonal cutback of the fan-like foliage is necessary to prepare the iris for its dormant period. This procedure occurs in the late fall or early winter, after the first hard frost has caused the leaves to yellow and die back naturally. Removing this spent greenery is a measure of disease prevention, as dead or decaying leaves are prone to harboring fungal spores that cause issues like leaf spot. Leaving foliage over winter creates an ideal environment for the iris borer, which lays its eggs on the foliage, allowing the larvae to hatch in the spring and bore into the rhizome.
Cut the leaves back to a height of about six to eight inches above the ground. Make the cuts at an angle, shaping the remaining foliage into an inverted “V” or fan shape. This fan cut helps prevent moisture from collecting in the center of the fan where the new growth emerges, which could lead to crown rot. Green foliage must remain intact until dormancy, as it is actively photosynthesizing and storing energy in the rhizome for the following spring’s flowering.
Necessary Equipment and Sanitation
Performing these cuts requires sharp tools to ensure clean and healthy pruning. A sharp pair of bypass pruners or sturdy scissors are the instruments for iris maintenance. Sharp blades create a clean cut that heals quickly, minimizing the surface area through which pathogens can enter the plant tissue. Dull tools crush the stem, causing damage that leaves the plant vulnerable to infection.
Tool sanitation is important to prevent the spread of bacterial and fungal infections between plants. Diseases like bacterial soft rot can easily be transferred via contaminated tools. Tools should be wiped down with a sanitizing solution, such as a mixture of one part bleach to nine parts water, or rubbing alcohol. Sanitize tools before starting work and especially between cutting different iris clumps.