How does a tree manage this if both sexes have to bloom at the same time? Scientists have discovered that all willows secrete an alluring scent to attract bees. Once the insects arrive in the target area, the willows switch to visual signals. With this in mind, male willows put a lot of effort into their catkins and make them bright yellow. This attracts the bees to them first. Once the bees have had their first meal of sugary nectar, they leave and visit the inconspicuous greenish flowers of the female trees.16
