When iris flowers fade, the plant’s next stage of growth begins, and proper maintenance during this period determines the success of the following season’s bloom. Gardeners wonder what to do with the spent flower stalks and remaining foliage. Immediate post-flowering actions are important for the health of the subterranean energy-storage organs, known as rhizomes. Understanding the plant’s biology during this transition helps ensure a robust display next year.
Removing the Flower Stem After Blooming
It is important to remove the spent flower stem, or scape, as soon as the last bloom on it has withered. This action, often referred to as deadheading, serves the primary purpose of redirecting the plant’s resources. If the stem is left intact, the iris will naturally begin to form a seed pod, consuming significant energy. This process diverts stored nutrients that would otherwise be used to strengthen the rhizome.
Use clean, sharp pruning shears to cut the stalk low down near the base of the plant. Cut the entire stem, leaving only an inch or two above the ground, but be careful not to damage the surrounding foliage or the rhizome itself.
Removing the stem channels the plant’s energy away from reproductive effort and toward vegetative growth. This redirected energy is then stored within the rhizome, which is the thickened, horizontal underground stem responsible for next year’s flower buds. A stronger, well-nourished rhizome is the direct precursor to larger, more numerous blooms in the spring.
Maintaining the Leaves and Foliage
A common mistake after removing the flower stem is to cut the green, sword-like leaves, but this foliage must remain in place for the rest of the growing season. The leaves act as the plant’s energy factory, performing photosynthesis to convert sunlight and carbon dioxide into sugars. These sugars are then transported and stored in the rhizome, building up the reserve needed to survive winter and produce next spring’s flowers. Cutting back healthy leaves prematurely starves the rhizome and weakens the plant’s ability to bloom next year.
The leaves should be maintained as long as they remain green and healthy, typically through the summer and into early autumn. Once the foliage naturally begins to yellow or turn brown, signaling the end of its photosynthetic activity, it can be safely cut back. Trim the leaves in late fall or early winter, cutting them back to a height of about six to eight inches above the ground. Trimming the leaves at an angle, rather than straight across, helps prevent water from collecting on the cut surface, which reduces the risk of fungal or bacterial diseases.
Essential Post-Bloom Care
Once the deadheading and foliage maintenance are complete, a few additional steps support the iris through its post-bloom recovery and energy storage phase. Proper watering is important, especially during dry periods, as the plant needs moisture to facilitate the transport of sugars from the leaves to the rhizome. While irises are generally drought-tolerant once established, deep, infrequent watering is better than shallow watering, which can encourage the spread of rhizome rot.
The best time to apply fertilizer is about four to six weeks after the blooming period concludes. A low-nitrogen formula, such as a 6-10-10 or 5-10-10 ratio, is recommended because it encourages root and rhizome development rather than excessive leaf growth. Apply the fertilizer sparingly around the base of the plant, ensuring it does not directly contact the exposed rhizomes. Keeping the area around the plants free of weeds and debris also helps maintain good air circulation, which is necessary to prevent pests and diseases from flourishing.