Tree Talk: All about firewood

There's something about sitting around an evening campfire, reminiscing about the day of hiking or hunting or simply spending time with family and friends. Any type of wood will do, just so it's perfect for s'mores. But if you are cutting or buying wood for your fireplace for a little romance or wood stove for supplemental heat, there are factors to consider.

Firewood differs in heat value as well as color of flame, fragrance and sparking, depending on the species of wood. Crabapple and apple have the most colorful flames, produce low smoke and few sparks. The most important characteristic of firewood for many homeowners is the heat value, measured in BTUs or British thermal units. One BTU is the unit of energy required to increase the temperature of one pound of water from 60 to 61 degrees. A gallon of propane is the equivalent of 100,000 BTUs, so a cord of green ash has the heat equivalent of about 200 gallons of propane. Here is a ranking of wood (common species in North Dakota) based on million BTUs per cord. "Hardness" (density) of the wood means more BTUs:

Bur oak tops the list at 25, followed by apple/crabapple, birch and juniper at 21, green ash and hackberry at 20, American elm at 19, boxelder and willow at 17, spruce at 16 and cottonwood at 14. Cottonwood is best for kindling as it burns quickly. Throw on some harder woods to keep the fire going. Take caution with juniper and spruce as that wood produces many sparks.

Firewood is purchased by the cord – a stack of wood 4 feet wide, 4 feet high and 8 feet long (128 cubic feet of space). Be careful about buying by the pick-up load since those quantities can vary. A 6-foot bed holds a fourth of a cord, while an 8-foot bed may hold a third of a cord. Wood should be seasoned – split, stored off the ground and protected from the elements for at least nine months. This eliminates moisture from the wood and prevents steam and smoke in the fireplace or stove.

Finally, and importantly, buy firewood from local sources when you are able to do so – less than ten miles away is best. There are plenty of shelterbelts in the North Dakota countryside with dead trees and most likely the dead trees will be elm, green ash and cottonwood. Movement of firewood has spread Dutch elm disease (DED) throughout the state since DED was first found in Mandan in 1969. Now, we wait as Emerald Ash Borer (EAB) inches ever closer to the state, another pest that is spread mostly through transport of infested wood. EAB has not yet been detected in North Dakota, but is established in Minnesota, Sioux Falls, and in Winnipeg. Buy or cut your own firewood where you burn it – or buy certified heat-treated and labelled firewood - to protect your favorite places from destructive pests.