Siberian Encores

The spell of really hot weather this week brought the Siberian bloom season to an end here. “What?” I can hear you say, “it ended for me weeks ago”. So it did for me -- except for the few irises that repeat bloomed. This ability of some Siberians to give a second round of flowers a few weeks after the first remains a mystery to me. It happens every year, some years better than others, but after many years of observing it, I have seen no obvious relationship to the weather during or prior to the bloom season. This year it was quite minimal even though growing conditions were generally favorable. Some have suggested that repeat bloom is due to late frosts that kill back some bloom stalks and result in the forcing of dormant ones, but there is no good evidence for this. Being well grown, mature clumps seems to be a necessary condition and there is certainly a genetic component to it. Most Siberians never repeat bloom, some do it occasionally, and a select few do it regularly. However, even they are not entirely reliable. You can have two well grown clumps of the same iris growing side by side – one will have several new bloom stalks and the other nothing. Further it may be that there are regional variations. Some reported repeat bloomers from the East Coast rarely do so for us in the Midwest, though there is no reason to doubt they do it on their home territory.

This leaves the hybridizer in a quandary. Obviously repeat bloom, if fairly reliable, is a positive trait, but it cannot be guaranteed every year in every location. So, should you make a feature of it in the description for sale? Should the name imply repeat bloom? Some hybridizers (myself included) could not resist. Examples are Bee Warburton’s “Reprise” and Marjorie Brummitt’s “Violet Repeat”. Currier McEwen designated at least a dozen of his Siberians as repeat bloomers at registration and named some accordingly e.g. “Welcome Return” and its children “Again”, “Blue Encore”, “White Encore”, “Ever Again” and “Exuberant Encore”. Elizabeth Scheffy’s “My Love”, an iris well known to repeat bloom, was a parent in the background of many of these. We have recently named “See Ya Later” and its offspring “Encore Performance” for their reasonably reliable capability under our conditions (note the genetic link again). Several others, not so named, also regularly repeat bloom for us and others, particularly “Coronation Anthem”, “Somebody Loves Me”, and some of its children such as our latest repeat bloomer, “Judy, Judy, Judy”. Several of the Shafer-Sacks introductions do this for us too, particularly “Dance & Sing”, “Dawn Waltz”, and “Sea of Dreams”.

Often repeat bloom consists solely of a few stems which, while interesting, does not provide a significant garden display. Can we breed to improve this trait? It seem reasonable to hope so because of the clear genetic factor(s) involved, but there seems to have been very little advance in its reliability and extent over the years since the topic was reviewed in the spring issue of The Siberian Iris in 1994. I have recently been making some crosses between our most reliable repeat bloomers with the primary goal of examining whether a focused breeding effort can improve its quality and reliability, so maybe we will see over next few years.

If you have any observations to add on repeat bloom, theories of why it happens, or information on what repeat blooms regularly for you, it would be great to hear -- and is anyone else breeding for this characteristic?