Something I wrote earlier this year to start it off.

Spring always brings surprises. My favorite surprise this year was found in every riparian area I wandered through. Every willow I saw seemed to have a different type of flower. Some had the familiar soft pussy willows, others had spiky, bright-green catkins, and perhaps the most confusing of all, a few appeared to have cones. This is my attempt to make sense of all the surprises willows brought me this year.

Willows are part of the family Salicaceae, genus Salix. (If I ever have a cat, which is not likely, I think I'll name it Salix.) They generally grow in wet areas and have flexible, thin branches and narrow leaves. Some species are shrub like while others can grow into larger trees. Reproduction in willows is the main point of interest here. Willows have male plants and female plants, in scientific words, they are dioecious.

The flowers of the male plants have catkins, long narrow clusters of flowers that have no petals. When these catkins first emerge, all you can see are the silvery hairs that come with each flower, or carpel. The silvery hairs are like a fur coat for the developing flowers, they allow heat in when the sun is shining and then protect the delicate flowers when it gets cold at night by trapping warmth inside. As the flowers develop, they emerge as little stamens full of yellow pollen to be distributed by insects attracted by strongly scented nectar in a gland at the base of the stamen. There are no showy flowers to attract insects but they are not needed in early spring when the market for nectar is hot.
The female flowers are also catkins, they have a a flat nectar gland and an ovary on the base of each scale that makes up the catkin. When the ovules are fertilized, seeds begin to grow and the catkin swells. When the seed capsules in the catkin burst, tiny seeds with fuzzy white hairs are released to bring us more willows next year.

At this point you may be wondering what those cones I mentioned had to do with anything. The answer is nothing. The cones are not really cones at all but galls formed when a tiny insect takes up residence at the end of a growing stem forcing the leaves that want to grow to become scales surrounding is very fortified home.

Point of clarification: There is a species of willow called the pussy willow, but the term usually applies to the furry catkins on any species willow.

References:
http://www.naturenorth.com/spring/flora/pwillow/Fpwillw1.html
http://insects.ummz.lsa.umich.edu/MES/notes/entonotes2.html