Curious about reblooming irises? Learn more about them here.
What are Rebloomers?
Reblooming iris produce more than one growth of bloom stalks in a single growing season. The cycle rebloomers complete two distinct cycles of growth, blossoming and increase in one growing season and produce the second cycle of bloom stalks from maturing new increases. The second growth and bloom cycle, usually beginning in late summer or early fall, does not require a chilling period, although cooler nights seem to promote more reblooms.
Rebloomers are found in bearded irises as well as beardless varieties. Beardless varieties are called repeaters. Many of the varieties of rebloomers can compete with the best of the single bloomers with range of color and size of blooms.
We have about 300 rebloomers out of 1,000 that should rebloom here in Colorado.
Where and When?
Various cold climate rebloomers rebloom from zone 7,(min. temp. 0 degree F.), to zone 6,(min. temp. -10 F), zone 5,(min. temp. -20 F), and zone 4,(min. temp. -30 F.). Warm climate rebloomers bloom only in warmer zones 8,(min. temp. 10 F), and zone 9, (min. temp. 20 F). Your rebloom results will depend on your cultural conditions, soil, and climate. Do not give up if you don’t get your rebloomers to rebloom the first year. Some varieties need to grow into a sizable clump and acclimate for a few years before they rebloom well.
What Special Effort?
Rebloomers take a little more care than single bloomers, but are definitely worth the extra effort. They like more water and fertilizer since they need an extra boost to flower again. You should fertilize them in early spring and again just after 4th of July. Don’t put the fertilizer directly on the plant but sprinkle it on the ground around root zone area. Use fertilizer with a low nitrogen content, such as 5-10-5, mixed 50/50 with super phosphate,(0-45-0). You can also use rabbit feed in pellet form.
Basically you do not want to let rebloomers go dormant. Water adequately at least once a week if rainfall is not sufficient. You may want to grow rebloomers separately from single bloomers because of the added water and fertilizer requirements of rebloomers.
Since most rebloomers increase faster than single bloomers, you may need to separate them every three years. Since some varieties need to be well established before they rebloom, you should divide and rest half of the clump and leave the rest to rebloom. Rebloomers are heavy feeders, so dig clump deeply to save as much roots as possible. Don’t fan the leaves, just remove loose leaves. When establishing rebloomers, do not cut back in late summer or they will not rebloom.
Although an iris is listed as having rebloomed in a particular state or USDA zone, there is no guarantee that it will rebloom in all gardens in that state or zone. Many factors influence flowering in a given garden: such things as cultural practices, soil type, fertility, years irises have grown in the same soil, disease presence or build up, and source of plants. All factors may affect flowering in spring and in reblooming later in the year. These are conditions over which we have no control.