The male flowers of Helwingia japonica. Small and not showy, they are still quite special; note that the flowers are emerging from the leaf, instead of the stem. This is a phenomenon called epiphylly. Here’s the text from the former interpretative sign about Helwingia japonica in the Garden: “Look closely at the upper surface of the broad, ovate leaves of Helwingia japonica in May and you’ll notice tiny green flowers arising from the centre of the leaf. Helwingia are monoecious shrubs, their separate male and female flowers arranged in tiny umbels. Rare in nature, epiphyllous flowers (Greek: epi = upon, phyllon = leaf) develop with their pedicels fused to the midrib of the leaf. This unusual arrangement is thought to be an adaptation that assists pollination by small insects. Helwingiaceae is a monotypic family (i.e., comprising only a single genus, Helwingia), with all three species native to the Himalayas and eastern Asia”.
Dr. Tim Dickinson of the University of Toronto has written a concise description of the developmental biology of epiphyllous growth in Helwingia, accompanied by images.
As mentioned on the interpretative sign, epiphylly is a rare phenomenon – a quick search suggested the condition occurs on some genera in perhaps a half dozen plant families, almost all of which are tropical. It’s very likely that UBC Botanical Garden is one of the few places in Canada you can see this phenomenon, although I note one nursery in Ontario is selling the plants (do a search for “Helwingia japonica” +Canada). If you’re visiting the garden, the most obvious place to find it is by the bench on the small meadow off of Lower Asian Way.
The garden has two of the three species in the Helwingiaceae in its collection, H. japonica and Helwingia chinensis. There’s a good distribution map for the family on the web page for Aquifoliales at the Missouri Botanical Garden. While visiting that link, be sure to click on the link that says “photo-fruit” immediately to the left of the map. Unfortunately, you can’t see the fruit at UBC – our plants are all male. One of our identified collection priorities for both research and education is to obtain a documented wild origin female plant of the species, as that is currently a gap in both the story that we can tell about this plant and what we can learn from it.