So, if there are not the variations between sharply colder nights, and

> warmer days, I do not think that the "sap pump" effect is going to be
> there.
> That said, bees also collect resins from areas of new growth.
> But trees may be unable to produce as much resin/sap due to a lack of
> colder
> nights.
>

I did not think that sap was much of a constituent of propolis.  Softwood
sap that is resinous seems to be more the result of bark injury than spring
sap flow.  There is definitely a time in spring when softwoods have a sap
flow, and you can peel them really easily at that time.  But the resiny
beads are on the outside all year.  My bees seem to use the most propolis
in fall, although robbing or a dead invader can get them going any time.
The resin from poplar buds is supposed to be an important source,  but it
is not readily apparent to me on the tree.  Most of our native poplar here
in PEI is trembling aspen.   There are a few non native Lombardi poplar
planted as ornamentals.  There is another non native poplar that I think is
called black poplar and is supposed to have medicinal uses.  It is not very
common here, but there is a row of them along a road.  In the summer that
stretch of road smells strongly like propolis.
Stan

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