What does catkin refer to in botany?

In botany, a catkin specifically refers to a type of inflorescence that is characterized by a cluster of male or unisexual flowers that typically lack petals. These structures are often associated with wind pollination and can be seen in various species, particularly in trees such as willows and oaks. The flowers are usually densely grouped along a slender, elongated stem, which gives catkins their distinctive appearance.

This feature distinguishes catkins from other floral structures, such as flowering heads, which might include many petal-bearing flowers, or stalks designed to support flowering. The absence of petals in catkins is a key characteristic that contributes to their classification. Further, a small underground root structure does not apply, as it does not relate to the floral structure or arrangement that defines what a catkin is.