Cladoptosis, abscission, and marcescence

I always enjoy finding a word that describes something I knew existed but for which I didn't know the term.  Today that word is cladoptosis.

Anyone who tends a garden (or just walks in a woods) knows that if tree branches are shaded by crown growth, those branches will drop their leaves, then eventually die when they no longer provide any net benefit to the tree.  

The etymology is straightforward: from the Greek κλάδος kládos "branch" [think "clade"], πτῶσις ptôsis "falling" [as in eyelids].

Related term: abscission (ab = away + scindere = cut) [think "scissors"] for the normal shedding of leaves (or other body parts that are no longer needed).

And the opposite term: marcescence (when a tree retains leaves that would normally be shed, as is common in some young oaks (pic at right).

The terms come into play when one spots a squirrel's drey high in a tree, retaining the dead leaves in midwinter because the branches were harvested to create the nest before the onset of normal abscission.

See also: Stars in tree twigs.  Top photo via Northern Woodlands.