Irises are cherished flowers, traditionally known for their spectacular display of color in the late spring. While most varieties bloom only once annually, the reblooming iris (or Remontant iris) has a unique genetic trait allowing it to flower more than once per growing season. This capability provides a second or even third flush of color, typically extending the bloom period into the late summer or fall. Supporting these multiple flowering cycles requires specific cultural practices.
Defining the Reblooming Cycle
A reblooming iris is defined by its accelerated growth cycle, which enables the plant to produce a new flowering stalk within the same year. A standard iris produces a main rhizome that blooms in spring, and its offsets only bloom the following year after dormancy. The rebloomer quickly develops new lateral fans, or increases, from the original rhizome during the summer months. These rapidly maturing growths are the source of the second set of flower stalks.
Reblooming irises are broadly categorized based on their specific flowering behavior throughout the season. “Cycle rebloomers” are the most common type, completing one full bloom cycle in the spring and a distinct second cycle in the fall. “Repeaters” produce additional bloom stalks immediately after the initial spring flush, essentially extending the spring season. “All-season rebloomers” are the least common, capable of sending up sporadic bloom stalks throughout the growing season, with timing often influenced by soil temperature.
Essential Care for Repeat Blooms
Achieving a repeat bloom requires more focused maintenance than caring for a once-blooming iris due to the increased energy demand. Rebloomers are heavy feeders, and proper fertilization supports a second round of flowering. Immediately following the spring bloom, the plants should receive a light application of fertilizer.
The ideal fertilizer is low in nitrogen and high in phosphorus, such as a 5-10-10 or 5-20-10 NPK ratio. Excessive nitrogen encourages soft, leafy growth prone to rot. Higher phosphorus content supports the formation of new roots and flower buds in the lateral fans, helping the increases mature quickly enough to produce a bloom stalk before cold weather.
Consistent moisture is necessary during the hot summer months when new fan growth must rapidly develop. Unlike standard bearded irises, which tolerate drier conditions after blooming, rebloomers need regular watering to prevent summer dormancy. Full sun exposure (at least six hours of direct light daily) and well-draining soil remain necessary. Poor drainage or deep planting can still lead to rhizome rot, even with increased watering.
Timing the Seasonal Displays
The first flowering period for reblooming irises occurs in the late spring or early summer, consistent with non-reblooming types. The timing of the subsequent bloom is highly variable, depending on the specific variety and regional climate factors. This second display usually occurs between mid-August and late October, stopping when the first hard frost arrives.
The reblooming trait is often triggered by high energy reserves and a shift in temperature, making it less reliable in extremely cold or consistently hot climates. Gardeners in cooler regions (USDA Zone 4 or 5) may see limited rebloom. Those in warmer zones (7 through 9) often experience more consistent, sometimes multiple, fall displays. The new fans must generate flower stalks before the growing season ends.