You feed 2/1 syrup when you want the bees to treat it as pure food, and
possibly store it away.  That is why 2/1 is fed in the Fall and Winter.
 
You'll sometimes hear 1/1 feeding called stimulative feeding.  You feed 1/1
syrup when you want to encourage the colony to increase in size (as well as
eat).   Hence, 1/1 is fed to new colonies, weak colonies, and in general when
we want to build up colony population.
 
1/1 is fed in early spring because we want to have the largest possible
colony for the honeyflow.   In Central Maryland, the honeyflow normally
starts sometime in the last two weeks of April, so we start feeding 1/1 about
the middle of February.  That way, the colony hits the honeyflow with the
maximum number of foragers.  Package bee producers will also stimulative feed
1/1 so they have lots of bees to sell.
 
But, before you rush out and stimulative feed, remember that until the
honeyflow starts, a large colony requires the most dilligent efforts to keep
from swarming.  And, if that happens, all you may get out of the 1/1 feeding
is an interesting phone call from your neighbor.
 
W. G. Miller
Gaithersburg, MD