Irises are perennial flowering plants, known for their unique structure and wide range of colors, which typically grow from underground stems called rhizomes. Whether these plants bloom more than once a year depends entirely on the specific variety being grown. While the majority of traditional iris cultivars produce flowers only during a single season, specific varieties known as remontant or reblooming irises are genetically predisposed to flower multiple times.
Understanding the Single Bloom Cycle
The standard bloom cycle observed in many popular iris types, such as the Tall Bearded variety, involves a single, intense flowering period. This cycle is driven by the plant’s energy management strategy, which relies on the rhizome storing carbohydrates over the winter months. Once spring arrives, the plant uses this stored energy to produce the single flower stalk, which typically occurs in late spring or early summer. After this main flowering event, the plant shifts its focus entirely toward vegetative growth for the remainder of the season.
The leaves continue to photosynthesize, replenishing the energy reserves within the rhizome. This annual cycle ensures the plant is robust enough to survive the next winter and repeat the single, high-energy bloom the following spring. This pattern is why standard irises will not produce a second flush of flowers in the same year.
The Phenomenon of Reblooming Irises
Remontant irises possess a distinct genetic makeup that allows them to accelerate their growth cycle and produce new flower spikes from secondary buds within a single growing season. These varieties still produce the initial spring bloom. The difference is their capacity to quickly develop new rhizome growth, which forms new bloom stalks later in the year.
The second flowering period, often referred to as the rebloom, typically occurs in the late summer or early autumn months. This secondary bloom is frequently less dense than the initial spring display. Success in achieving this second cycle is often tied to environmental factors, as summer warmth followed by cooler temperatures can act as a trigger for new flower formation. Reblooming is most reliable in regions with mild climates and long growing seasons, where the plant has sufficient time to rebuild its energy stores between flowering events.
Essential Care for Repeat Blooms
Achieving a repeat bloom from remontant irises requires a more rigorous care regimen than that of their single-blooming relatives, due to the increased energy demands placed on the plant. Since these varieties expend energy for multiple flowering events, they require consistently higher levels of moisture and nutrients throughout the growing season. Applying a balanced, low-nitrogen fertilizer immediately following the spring bloom helps the plant quickly replenish the resources needed for the second cycle.
Proper deadheading maximizes the potential for a rebloom. Once the spring flowers fade, the spent flower stalks must be promptly cut down to the base of the plant. This action prevents the plant from wasting energy on seed production and redirects resources toward the development of new growth and subsequent flower spikes. Providing the plants with at least six to eight hours of direct sunlight each day is also necessary, as full sun exposure is required to support multiple bloom cycles.