Often overlooked, birch seeds are distinctive and easy to find on a snowy forest floor

Published January 26 2022 in the York Weekly, Portsmouth Herald, Fosters Daily and online at seacoastonline.com

Even though I am sure I have seen these all my life, I don’t remember ever noticing the actual seeds of birch trees until relatively recently.  This is one of those things that is so easy to overlook, but so easy to observe on a snowy winter’s day.

The seed-producing parts of our local birch trees are borne on catkins. 

Birch trees have both male catkins (which dangle) and female catkins (which stand erect) on the same tree. Male catkins release pollen in the spring which blows around until it encounters and then pollinates a female flower-female catkins are simply clusters of birch flowers.   As the seeds within the female catkin mature, the catkin starts to droop as it prepares to release the seeds.  The seeds (also called nutlets) are winged structures that are so lightweight that they can be carried quite far away and don’t have hard shells (like an acorn), so they germinate quickly–this is why birch trees are often the first trees to colonize after a fire or other disturbance (hence the term “pioneer species”). 

A fallen female catkin with the oval, winged seeds and bird-like bracts scattered around. Sue Pike Photo

If you take a walk in a snowy field (or forest) amongst some birch trees, look down.

  You should see tiny things in the snow, little seed-like structures.  Look closer-you’ll see tiny oval seeds (or nutlets as they are called) with tiny translucent wings and other tiny things that look like silhouettes of birds flying-these are the leftover protective structures of birch seeds. These are bracts, modified leaves that protect the birch flowers. When you see one of those dangly catkins hanging from the tip of a birch branch, what you are seeing is an overlapping series, a cylindrical column, of these bracts, protecting the seeds. The bracts look like they have wings, but compared to the seeds they are heavy-they don’t need to travel as far as the seeds.

Giant yellow birch bract on the left dwarfs the two tiny gray birch bracts Sue Pike photo

Different birch tree species can be distinguished by those protective bracts.  Gray and paper birch seeds are protected by bracts that look, to me, like soaring birds–two outstretched wings, a head and a tail.   Yellow birch bracts look like bird tracks to me– bird tracks with 3 toes and are  much larger than paper and gray birch seed bracts. 

Hopefully we will have more wintery weather here in the Seacoast. 

The snow gives us an opportunity to see things that are normally hidden.  The next time it snows, you really must go outside and see for yourself.  You will need a patch of snow and some birch trees.  Look down.  Look for little soaring birds.  Look for tiny pieces of flotsam that look like bird tracks.  Then look around and you’ll find some birch.

Read more about birch seeds and bracts at naturally curious and birch ID at maine.gov