The genus Populus includes poplars, as well as aspens and cottonwoods. While there are a number of native poplars in Massachusetts, others, such as the white poplar (Populus alba), have been introduced from elsewhere in the world. Although it has not spread to nuisance levels in Massachusetts, some states, including Connecticut, have placed white poplar on their invasive species list. 

Superficially, many poplars resemble each other. But white populars can be easily distinguished from other related species. The most obvious trait is the white fuzz covering the undersides of white poplar leaves. In fact, it was a fallen leaf with its white side up on the trail I was walking this morning that caught my attention. Mature leaves have a shiny green upper surface with a downy white covering only on the underside, but when the leaves first emerge in the spring, the entire leaf is covered in this downy fuzz. In addition to the unique undersides, the alternate, blunt-toothed leaves of white poplar often take on a 3- or 5-lobed appearance, somewhat resembling a maple leaf, and the leaf stalks of a white poplar leaf are round. This round leaf stalk can help distinguish it from quaking aspen (Populus tremuloides) or big-tooth aspen (Populus grandidentata), which both have flattened leaf stalks, causing the leaves to readily flutter or “quake” in the wind. 

On mature white poplars, the upper part of the trunk is whitish and smooth, while the bottom part of the trunk is blackish and furrowed. They can grow to between 60 and 100 feet tall.