Irises are celebrated garden perennials, prized for the striking colors and unique form they bring to the spring landscape. Gardeners often wonder if it is possible to enjoy these flowers more than once in a growing season. The answer is yes, but the ability to produce a second flush of blooms depends entirely on the specific variety of iris planted. For varieties with this genetic capacity, careful gardening practices are necessary to support this energy-intensive process.
The Core Distinction Between Iris Types
The capacity for a second bloom is a trait determined by genetics, separating irises into two main groups: standard once-blooming varieties and reblooming varieties. Irises that can flower multiple times are known as remontant varieties. This characteristic is a specific genetic inheritance that allows the plant to shorten its growth cycle.
The vast majority of irises, including many common Tall Bearded Irises, are once-bloomers that focus energy on a single spring display. Remontant irises are bred specifically to produce a spring bloom and at least one additional cycle later in the year. These reblooming genetics are found primarily within the Bearded Iris class, including Standard Dwarf Bearded, Intermediate Bearded, and Tall Bearded types.
Beardless irises, such as Siberian or Japanese varieties, are not typically true rebloomers but are sometimes classified as “repeaters.” Repeaters extend the spring bloom period with additional stalks emerging shortly after the first flush. They do not provide a separate bloom season later in the summer or fall. The reblooming trait is most reliably expressed in selected remontant Bearded Iris cultivars.
Understanding the Rebloom Cycle
The rebloom process accelerates the plant’s normal life cycle, requiring two complete cycles of vegetative growth and flowering in a single season. After the initial spring bloom, the central rhizome produces new offsets or “increases,” as the central rhizome flowers only once. These new fans of foliage must grow quickly throughout the summer to store enough energy for the secondary bloom.
The secondary bloom occurs in the late summer or autumn, triggered by cooler temperatures and increased moisture. This second bloom emerges from the newly grown fans, which do not require the prolonged period of winter chilling, or vernalization, that initiates the spring bloom. This ability to bypass the cold requirement is a genetic difference enabling the plant to bloom again out of season. Since the plant performs twice the work, the reblooming cycle places a high demand on its resources.
Essential Care for Encouraging Rebloom
Successfully achieving a second bloom demands more attentive care for reblooming varieties compared to their once-blooming counterparts. The most significant difference from standard iris care is the need for consistent moisture throughout the summer months. Rebloomers must be kept consistently watered, receiving about one inch of water per week, especially during dry spells. Allowing the plant to go dormant due to lack of water during the summer prevents the formation of the new fans needed for the secondary bloom.
A precise fertilization regimen is also necessary to replenish the energy used in the initial spring bloom and support the rapid growth of new fans. After the spring flowers fade, apply a low-nitrogen fertilizer, such as a 6-10-10 or 5-10-10 NPK ratio. Low nitrogen is important because high levels encourage lush foliage growth, making the plant susceptible to soft rot, especially with increased watering. The higher phosphorus and potassium content promotes strong root development and flower production.
In addition to watering and feeding, maximum sun exposure is required, ideally a minimum of six hours of direct sunlight daily, to fuel the accelerated growth cycle. Promptly removing the spent flower stalks, or deadheading, after the spring bloom redirects the plant’s energy toward producing new rhizome increases instead of setting seed. While the flower stalks should be removed, the green, sword-like foliage must be left intact, as it is responsible for photosynthesis and manufacturing the energy reserves needed for the autumn flowers.