Big-toothed Aspen

Big-toothed Aspen (Populus grandidentata) is fairly abundant around our house, lining the discontinued dead-end dirt road on which we live and showing up occasionally along the paved nearly-two-lane back roads. Fifty years or so ago, pastures and hay fields characterized farmland whereas only a few open farm fields remain today. Where the Big-toothed Aspen stand, you can see the fairly even ground in contrast with more dramatic hummocks and hollows pocked with boulders in less accessible areas of the forest.

In an early successional forest, pioneer species such as Big-toothed Aspen (P. grandidentata), Quaking Aspen (P. tremuloides), Gray Birch (Betula populifolia), and Paper Birch (B. papyrifera), establish where there is abundant sunlight after a landscape has been disturbed by fire, agriculture, or logging. Over time, other tree species take root and reach up into the canopy, out-competing the pioneers who are intolerant to shade.


Most of the Big-toothed Aspen's branching occurs high in the canopy where the leaves reach for solar energy used by chlorophyll to convert carbon dioxide (from the air) and dissolved minerals (from the roots) into sugars (photosynthesis). Oxygen is released in the process which makes plants, in general, a nice complement to us humans who exchange the oxygen for carbon dioxide.


The Big-toothed Aspen leaves flutter in the wind, a function of the flattened petioles (leaf stems). A side note, the fluttering gives this tree's Genus-mate Quaking Aspen (P. tremuloides) its common name as well as its species designation. Another side note, a third Populus species, Balsam Poplar (P. balsamifera) has a rounder petiole that does not catch the wind in such a shaking manner.  You might notice that aspen and poplar are used interchangeably for this genus.



Moving down the Big-toothed Aspen's trunk you might notice that the bark is very light-colored, like Paper Birch or Gray Birch. Closer inspection reveals a slight greenish tinge from chlorophyll that allows the bark to photosynthesize, a little bit anyway. On a Paper Birch, the white bark peels horizontally in thin strips that you'll never see on a Big-toothed Aspen or Gray Birch. Paper Birch and Gray Birch have lateral black lines, lenticels, that allow for gas exchange. The Big-toothed Aspen lenticels are more diamond-shaped, like little stars. The birches have a black chevron where the branches come out from the trunk - not as prominent on the Big-toothed Aspen.


If you follow the trunk down to the ground, you might be surprised to find the bark transitions to furrows and ridges! The ridges are quite distinctively chunky on older trees (see photo below with pencil for scale). On tall but less mature trees (like the photo on the right, below), the bark has been described as "zebra-like" with a light colored base laced with emerging, darker ridges.

And, of course, there's always the leaf. In spite of its tattered appearance, it's easy to confirm this aspen's identity and its names, both common and technical - Big-toothed Aspen, Populus grandidentata!