I know 'green' wood has to be seasoned for at least two years (and preferably three) before burning. Unless it's ash which can be burnt straight after cutting I'm told. The tree we took down was an evergreen fir, possibly a Lleylandii (not sure of the spelling). A friend with a central heating boiler which can run on either oil or wood had problems after burning this type of wood. It reduced the width of his flue to about a 2" diameter and carbonised to such an extent that they has to dismantle the chimney tubing and knock out the blockages. Hence, I've always avoided trying this type of wood, sticking to beech, oak, elm or chestnut (all of which are available locally). Maybe he was burning this wood at low temperatures, but I'd rather not risk it. BTW, never put chestnut logs on an open fire unless you want run all over the room, stamping out glowing embers spat out like speeding bullets.
@Huevos : No, both the log burner and the Rayburn are just straight tubing. The log burner does I think have secondary combustion, certainly it's very efficient but I really use it for background heating. The Rayburn runs mainly on anthracite but can burn logs too. It's easier to keep it in all night with anthracite, a big plus as I cook on it and it heats four upstairs radiators and a shower room towel rail.