Yellow Birch Catkin (Updated)

Yellow birch is monoecious--male and female catkins are borne separately on the same branch.

Here are the male pollen catkins. They look this way through the winter and are expected to lengthen and mature come spring. The female fruiting catkins have yet to form.

Here is another example of specimens that I collect and photograph without knowing anything about them. We looked at a rather large Yellow Birch some time ago and I didn't notice any catkins at that time. (I'll have to check on that.) This ID was about two weeks in the making. What confused me was that these catkins were collected from bushes only six feet high, meaning that sexual maturity must come early with this species.

Update: 11 Jul 2009. These are the male catkins of the Hazelnut.