Re: Availability of pollen in early spring:
 
  In southeastern Pennsylvania, bees work skunk cabbage (pale green pollen)
and (non-native, but widely-available) snowdrops and crocuses.  When the
tiny red flowers of soft maples (red and silver maples) bloom, winter has
ended for the bees.  Squirrels chew off some of the red maple flowers,
allowing the beekeeper to check on the bloom by picking up flower clusters
from the ground. The flowers have yellow stamens and yellow pollen.
 
    Last year, maples around Philadelphia were in bloom on March first.
This year, the bloom began this past week.
 
    (Bees in southeastern Pennsylvania usually begin to swarm when the
petals fall off the apple flowers and stop swarming when tulip poplar bloom
ends.)
Tim
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Tim Sterrett
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(southeastern) Pennsylvania, USA
40.0 N 75.5 W