The Texture (and Abundance) of Birch Seeds

18 April 2012
9:25 PM

Sunrise at	6:03 AM	in direction	61°	East-northeast
Sunset at	9:40 PM	in direction	300°	West-northwest

Duration of day: 15 hours, 37 minutes (6 minutes, 53 seconds longer than yesterday)

I am not a biologist, but simply observe the birch like I do all plants because plants are always of interest to me.  Anything I say is based on impression, rather than study. I am not attempting to quantify or categorize birch, but rather describe one aspect of my life - and in particular my life among birch trees.

Birch seeds resemble the chafe tossed away from wheat.  Paper thin, they grow in clusters, packed between catkin bracts on the tree as shown in the photo from Healthy Home Gardening, White Paper Birch.

The seeds dry in extremely small flowers.  The photo below is not true to size.  I held up a birch seed pod next to the photo and it was less than 1/5 the size shown.  When clusters release in winter, the ground below can be completely blanketed with them.  They give the appearance of a layer of saw dust in color and texture.

Yet, they can be so thick on the deck that I have swept enough of them to fill a shopping bag.  I consider them among the most generous of plants because they provide food for seed eating birds throughout winter.  Although feather light and giving a dry appearance, they are able to stick to each other, dog paws, and shoes easily.  When I sweep them up, they softly cling to each other, yet settle more densely than you'd expect.

There is very little wind in the subarctic interior of Alaska, so paper birch do not rely on that to disperse seeds.  Gravity pulls at the seeds clusters, like it pulls at all things on the surface of the earth, so as the seed pods age, there is a point at which they outweigh the tensile strength of the seed cluster stems and they cascade to the ground.  The slightest breeze may encourage the release of seeds, but not necessarily.  I have seen twigs strewn about the yard, having snapped from being brittle in a slight wind at subzero temperatures, but not found many seeds on the snow.  I am guessing the deep, dry cold of hoarfrost and hot dry sun hasten conditions for their release the most.

Raised in the mid-latitudes of Western United States, my observations of the native species and cultivated species of the region are that they dispersed seasonly.  But the birch seed clusters form in autumn and continue to disperse all through the winter, spring, and summer.  It's possible for them to disperse seeds even while forming new pods in the fall.  There is no time we don't have birch seeds falling in our yard and on our deck.  There is no time when birch seeds are not being tracked into the house.

While birch will not grow in regions of permafrost and are not competitors with black spruce, they are not the final species in plant succession.  Despite the abundance of birch seeds, white spruce seedlings like the shady understory provided by birch and aspen and since they grow very fast, soon can outstrip the birch trees in moist soil.  But birch do better in some terrains than some species of spruce and it can take a good while for spruce get a hold against the prolific birch trees.

Our yard is one of the moist regions near permafrost, so we have strong stands of spruce in the south east.  We cut the spruce away from the house (defensible perimeter) and when necessary, keep it to a minimum in the south and west for winter light.   So far, the birch are holding their own in that region and as long as I live here, the succession of species will be somewhat slower on our lot.