Tuesday, September 9, 2014

Mighty Oaks from Acorns Grow

Once every few days or week I log into Nature's Notebook (NN) to continue my contribution to citizen science.  NN is a long-term project of the National Phenology Network, in which ordinary citizens track seasonal changes in plants and animals nationwide, to provide data to scientists interested in, for example, the rate at which climate is changing, and how living things are adapting--or not.  Most of the half-dozen or so species I track in my neighborhood are trees, and big trees, at that.  So I am mildly frustrated to come to the following questions on the data sheet: Do you see pollen release?  Do you see fruits?  Do you see ripe fruits?  The fact is I seldom see any of these, mainly because they are too too far away up in the tree's canopy.

A thunderstorm last night finally wetted the dusty ground here and might perk up the wilted leaves for a day, but it had another helpful side effect: it knocked down a few twigs from a majestic but inaccessible red oak on the other side of my block. Finally I got a look at something I seldom see: baby acorns.  

Branchlet of red oak (Quercus rubra).  The developing acorns are invisibly small here, 
but you can make them out in the photo below.

Here are three or four acorns in the axils of the leaves, while buds (for comparison) are at the tip of the twig.

When I first saw these on a fallen twig a few weeks ago, I first thought they were deformed buds.  I had to stare at them awhile and finally decided they must be acorns. 

 The previous photo, cropped.  At the tip of each acorn, you can just make out 
the three curly stigmas left over from the female oak flower.

The acorns are curiously small so late in the season, until you realize they will not finish maturing until next summer.  

Red oak belongs to the group of oaks that takes two years to mature its acorns.  Called the "red oak group," these oaks have leaves with pointed, bristle-tipped lobes.  Around here, they include scarlet oaks and black oaks as well as red.  

Scarlet oak (Quercus coccinea).  Another tree, pin oak, has similar leaves 
("more hole than leaf"), but lives in wetlands.

Black oak (Quercus velutina) has a leaf with fewer and broader lobes than red oak,
and is less deeply-cut than scarlet oak.

The acorns of red oak are broad faces wearing berets.  
The acorns of the red oak group mature the second year, so these came from last year's flowers.

Acorns of white oak have thinner faces wearing  knit caps.  They mature the same year, and are sweeter and more readily edible than acorns of red oak, etc. 

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