Green Wood

I know the old guys like my dad who used smoke houses used green hickory because they wanted it to smolder and never really burn and get hot. They would "cold smoke" hams and bacon for days to just cure the meat.

Hot smoking and cold smoking
"Hot smoking" is a several-hours-long process that can be used to fully cook meats or fish; barbecue is a form of hot smoking. Generally, hot-smoking involves holding the food directly above the fire, or in an enclosure that is heated by the fire. The cooking temperature in a hot-smoking environment is usually between 55 and 80°C (130–180°F) The temperatures reached in hot smoking can kill microbes throughout the food.

"Cold smoking" is an hours- or days-long process in which smoke is passed by food which is held in a separate area from the fire. Generally the food is held at room temperatures (15–25.5°C/60–80°F) as it is smoked. Since no cooking takes place, the interior texture of the food generally isn't affected; neither are any microbes living within the meat or fish. For this reason, cold-smoking has traditionally frequently been combined with salt-curing, in such foods as ham, bacon, and cold-smoked fish like lox (smoked salmon).

Source: Wikipedia http://en.wikipedia.org/wiki/Smoking_(food)

I think the gasser pits like oh, southern prides etc recommend green wood so it doesnt just ignite and disappear in a few minutes with the flame thrower charging the chamber. The green will smoulder for a while.