In article ,
Andrew Heggie wrote:

Hardwoods to avoid for poor burning (mostly simply high moisture
content) poplar, willow, elm, holm oak and turkey oak.

I cut down a few large willow trees (not weeping
willow) a few years ago and they seem to have seasoned
into quite an acceptable wood for the woodburner.
Weeping willow seasons ok to a low moisture, but feels
quite light, and without much calorific value.

--
Tony Williams.