Karl Foord, UMN Extension Educator
I took a closer look at bearded irises this past week and two things intrigued me.
The first thing that intrigued me was the amazing variation in iris petal and beard colors (photos 1-4). It was also interesting to observe the change in beard colors throughout their length as they moved from the exterior part of the petal to the interior part of the flower (photos 5-7).
The second was a question of how did this flower actually work given the very obvious and showy petals and the less obvious male stamens and female pistils. The iris flower has a unique structure whose purpose is to avoid having pollen from this flower's male stamens transferred to the same flower's female stigmatic surface and pistil. As the bee enters the flower tracking along the beard it passes a flap that the insect will push past and fold back exposing the moist receiving part of the stigmatic surface capturing pollen on the hairy back of the insect. As the bee continues toward the nectarines and sugar reward it then passes under the anther picking up pollen on its back. When it has finished feeding on the nectar and begins backing out of the flower, the stigmatic fold is pushed the other way exposing a dry non-receiving part of the stigma and thus transfers no pollen from this flowers anthers to the same flowers stigmatic surface (photo 8). Can you identify the same flower parts in photo 9?
The system is not foolproof, however, because the same insect could visit one of the two other parts of the same flower, or another flower on the same plant.
Note: all photos taken at the Minnesota Landscape Arboretum.