Betula lenta

Family / Families: Betulaceae
Scientific Name(s): Betula lenta L.
Institution(s): Carolinian Forest, University of British Columbia Botanical Garden
Accession Number(s): 2007-0323
Location(s): Vancouver, British Columbia, Canada
Entry Author(s): Dominic Janus
Copyright Holder(s): Dominic Janus
Image License: Creative Commons License
Tags: Betulaceae, Fagales, named by Linnaeus, Photo by Dominic, UBC Botanical Garden

Late autumn foliage of Betula lenta

I’d describe this late October afternoon in the Carolinian Forest Garden as a classic autumn experience. It was impossible to not be still and appreciate the sunlight in harmony with the yellow leaves of Betula lenta.

These dark-barked trees also centre this photograph, standing among the sea of yellow of their shed leaves. Betula lenta, or sweet birch, is also known as cherry birch due to the resemblance of the dark bark to the bark found on some cherry trees, while the sweet birch common name originates from the sweet wintergreen scent of the leaves and bark. For many years, Betula lenta was the only source of wintergreen-scented oils. Production of wintergreen oil can now be done synthetically, no longer requiring the harvest of sweet birch that was once very common in the Appalachians. Approximately one hundred saplings were required to produce one quart of wintergreen oil.

Sweet birch is native to eastern North America, ranging from Maine to Georgia. In many sites, it replaces American chestnut where that once-prominent tree grew in numbers. In Canada, though, the species is listed as an endangered species. It is known from only one vulnerable population in southern Ontario, where only 18 individual trees remain, half of which were planted onto residential lawn. A recovery strategy has been developed for this population along the Niagara shoreline. Habitat degradation has been the primary difficulty, including shoreline erosion of Lake Ontario. Erosion was responsible for all of the mature trees in this population being killed after severe storms 13 years ago. Strict habitat protection and planting of seedlings have been the only recovery measures listed so far; restoration into adjacent areas would be difficult as few natural areas are nearby.

Sweet birch reaches heights of up to 25 m (82 ft.) in the wild. Trees are usually smaller when cultivated. The glossy leaves are borne on tough but pliable twigs (defining the lenta part of the name). Flowers precede leafing out in spring. The presence of large vertical cracks in the bark of some mature trees is a species-specific feature compared to other common birch species; it can be a crucial feature in differentiating it from Betula alleghaniensis (yellow birch), which has almost identical foliage. Betula lenta apparently has one of the highest susceptibilities to Nectria canker. Some prevalent insects (with memorable names) known to attack the leaves are the birch skeletonizer (Bucculatrix canadensisella) and birch tubemaker (Acrobasis betulella). More details on pests and pathogens can be found on a USDA Forest Service page for Betula lenta.

Although maybe not the “perfect picture” that I had hoped for, I knew I’d be missing a great moment if I didn’t try to capture this scene. For me, it was the essence of an Ontarian deciduous forest autumn that I now rarely get to experience, with its key elements of sunlight, warmth, and a blast of colour. I have many memories of long walks in autumn woods such as these with their special ambiance. I wouldn’t dare try to compare it to autumn in the predominantly coniferous forests of British Columbia that I now call home; they’re each charming in their own way.