I was reminded of the Hunt Institute for Botanical Documentation‘s database of digital public domain images when updating the entry on Camassia quamash subsp. walpolei this morning. We haven’t featured a botanical illustration in a while, so I started to look through Walpole’s other illustrations, and found this one of Betula kenaica.
Betula kenaica, Kenai birch, is ranked at the species level in the Flora of North America, but the more recently published The Genus Betula by Ashburner & McAllister speculates that this taxon is actually an uconfirmed complex hybrid of paper birch (Betula papyrifera), Asian white birch (Betula pendula subsp. mandshurica), and other hybrid birches. The USDA PLANTS database ranks it as a variety of Betula papyrifera. Putative hybrids sure make things taxonomically messy! In comparison to Betula papyrifera, Betula kenaica differs “primarily in its smaller stature and in its smaller, blunter-tipped, more coarsely and regularly serrate leaves” (in Ashburner & McAllister). Hultén in his Flora of Alaska and Yukon writes:
B. kenaica is characterized by resiniferous twigs, thick dark green, often double-serrated leaves without prolonged apex with cuneate or truncate base, usually more or less hairy on the upper side and with appressed longa hairs in the margin towards the base.
As the common name implies, Kenai birch is native at least to the Kenai Peninsula, Kodiak, and adjacent parts of Alaska. Other reports indicate its range extending into Canada’s Yukon Territory, but Ashburner & McAllister (if I have read their account correctly) assert that these may be part of a larger hybrid swarm with other Betula papyrifera. In other words, to see the plants that best represent the taxon, head to the Kenai or Kodiak.
You can also read more about Walpole via the Hunt Institute for Botanical Documentation. He was a botanical illustrator employed for too brief of a time by the US Department of Agriculture for the US National Herbarium (he died at 43). Perhaps of some interest is this story about the fate of some of his illustrations: Recovery of Botanical Drawings Missing from the Botanical Art Collection.