Firewood dealers often offer "firewood mixes" to consumers that include softer woods, such as poplar and aspen, mixed with hard woods, such as oak or maple. These softer woods burn more quickly, produce less heat and may smoke or produce unpleasant odors. Free poplar firewood is one thing, but if you're paying for it in a mix, make sure you understand the percentage of poplar to other woods. That great deal on firewood may not be such a great deal if it is mostly comprised of poplar.
Identifying poplar firewood by sight alone is difficult, since it resembles oak. Keep in mind, though, that poplar grows quickly and is often harvested while the trees are still fairly young. The wood may not be split, but rather cut whole into 2- to 3-foot lengths. The round logs are often only 5 to 8 inches across. The bark, if left intact, may be brownish gray or even white, depending on the poplar variety.
One way to identify poplar is by cutting or splitting it. Poplar is a light wood that splits very easily, with few flying wood chips. Unlike pine, it doesn't produce a lot of resin or sap, and its bark is fairly soft and smooth.
Compare the wood in question to other hardwoods to determine if it is poplar. Poplar lights easily and burns quickly with few sparks and very few coals. It may produce some smoke or an off-odor. Because it burns so quickly, it doesn't produce much heat.
Despite poplar's reputation as a poor firewood, it does have some advantages. Poplar works very well as kindling. It splits easily into small pieces and lights quickly. Poplar trees are prone to winter damage and tend to drop wood. If you have a poplar tree on your property, you should have an ample supply of kindling from the debris that collects at the bottom of these trees.
When buying firewood, choose a reputable dealer that's been in business in the area for a long time. Ask for references and avoid buying firewood mixes if possible. If buying a firewood mix, ask for a written description detailing the percentage of wood types in the mix. If you have access to free poplar wood, by all means use it, but mix it with a hard wood if possible for more efficient fires.