Greenwood is freshly cut, unseasoned, wood. The moisture content of greenwood varies greatly from one type of wood to another. For example, green cottonwood has 140 percent moisture content, whereas fresh cut green ash has about 55 percent moisture. Air-drying wood to about 20 percent moisture requires up to 9 months and makes the wood acceptable for burning in an ordinary wood-burning stove or furnace. For more on this, see seasoned wood.
Burning green wood provides only a portion of the potential heat value of the wood and contributes to smoking and creosote-tar formation in the flue. Appliances can be designed, however, that will efficiently burn greenwood. For more on this, see greenwood chip furnace.