Andrew wrote:

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

....but if well dried/seasoned are OK. We have been burning lots of aspen
(=poplar) over the past couple of years simply because we had some large
aspens felled. Now, after two years or so and especially after this
years hot dry summer, it burns well.

--
Chris Green )