I recently concluded an expedition to Japan with Miles Sax, and thoughts of gathering seeds are fresh in my mind. In Honshu’s Yamanashi Prefecture, we happened upon one of the biggest Cercidiphyllum japonicum I’d ever seen. With a diameter of 5.5 feet and a height approaching 100 feet, it lorded over nearby trees with incredible majesty.
After returning to the Arboretum, I admired some of our oldest katsuras along Meadow Road. Far less stately but no less marvelous, accessions 882*A and *B also hail from Japan and date to 1878. They were collected by William Clark, who was in Japan to help establish the Sapporo Agricultural College (now Hokkaido University).
Katsuras are a treat in autumn, with golden-yellow, heart-shaped leaves and the aroma of burnt sugar tickling the nostrils. Winter is the best time to admire the multi-stemmed form, each bole sloughing silvery-gray bark in narrow rectangular sheets. Assuming you happen upon a female tree, you can also marvel at the small fruits attached to short-shoot spurs. Green in late summer, by autumn the curved follicles, nearly an inch long, have dried and split open to reveal the small, papery, winged seeds within. In midwinter, you can still see some seeds clutched inside. With each gust, a few spill out to be dispersed by wind and gravity. And if they land upon the snow, the seeds skitter away. It is a wonderful dispersal strategy, shedding seeds for weeks, even months, at a time, maximizing the chances of finding that perfect combination of moist fertile soil and light, a safe space not only to germinate with ease but to survive well into maturity.
Honestly, katsura seeds need little coaxing to germinate (a few weeks of cold, moist stratification does the trick), something I learned as a graduate student at Iowa State University. This was actually the first time I “sort-of” met the Meadow Road trees. I needed plants for experimentation and the Arnold, a ready source of germplasm, was a supplier. In September of 1996, large plastic bags of fruits from Accession 882*B (as well as 1150-67*A and 13008*A) showed up in the mail. Over that winter, I conducted a bunch of germination experiments, and by spring, I had a greenhouse crammed with hundreds of vibrant katsura seedlings.
Whenever I see those fruits in winter, I know of the countless seedling promises clasped within. I rarely resist the urge to tap the branches, shaking a few seeds out and into the breeze.
Michael S. Dosmann is the keeper of living collections at the Arnold Arboretum.