Architecture for Time Release

Drawing seed pods has taught me something about pod architecture:  it seems to be designed for time-sensitive release of seeds.  I don't know if this is true, but evidence points towards it.  On the left here is a blasted open pod from a yucca plant.  The shiny black seeds are stacked like checkers in neat columns in the sections of the pod.  The pod doesn't fall to the ground, but instead it splits open along lines of dehiscense and the seeds fall to the ground near the base of the parent plant.  The same seems to be true of the Japanese iris pod at bottom right.  But the beautiful pink and orange berries that were on a bush contain their seeds inside.  These tiny seeds remain inside the ripening berries like any other fruit.  Probably birds eat these berries and carry the seeds away from the parent plant where they drop them in their poop.

The hosta pod on the left works like the yucca and Japanese iris-- dehiscent pod splits open at a certain point in the drying out of the pod (and maturing of the seeds), flat seeds float and are maybe carried on the wind a bit before dropping.  We all know how it works for maple wings with their elegant little helicopter twirling down. 

But the lumpy black walnut at bottom right is the most interesting to me right now.  I found this one in the woods today in a perfect state of transition:  the outer hull, which contains astringent and bitter-tasting tannin, has almost completely rotted away (also thanks to the tannin) now that the squirrels and other nut gatherers have gone into hibernation.  The hard inner shell is now safe for the winter, until the longer days and warmer temperature and moisture of spring trigger the growth of the tiny seed inside.  When the seed begins to grow, the enormous force generated will crack the walnut shell open along dehiscent lines, and the seedling will grow into one of the ten thousand black walnut trees that we spend all summer trying to eradicate from our gardens and yards.