With flowers in bursts of orange and red, flame azaleas attract several types of pollinators. But these azaleas must rely almost entirely on butterflies to reproduce, researchers have found.

The anther and the stigma — the male and female parts of the flower where pollen is produced and then germinated — are too far apart for other insects to be effective.

“In order for a plant to reproduce, a pollinator — usually an insect — has to spread the pollen from the anther to the stigma,” said Mary Jane Epps, a biologist at North Carolina State University and a study author.

With the flame azalea, the distance “meant that it was unlikely for a bee or other small pollinator to come into contact with both anther and stigma during a visit,” Dr. Epps added.