A Shady Character: Japanese Cobra Lily
Joe Gadbois, May 26, 2025
Whew! It’s a been a while since my last post, but I haven’t forgotten about the Garden Blog! The last few months have been a bit of a whirlwind. I was in the Perennial House looking at our Japanese cobra lilies recently, and I mentioned to my beloved co-worker Martha that mine has now survived 2 winters at my new home in Sturgeon County. She suggested that I write about it, and here we are! Maybe I can do less than 5000 words this time!
Yes, the Japanese cobra lily is special enough to dedicate a blog post to. Known to the botanical community and plant aficionados as Arisaema sikokianum, it is a member of the Arum Family, a group of plants collectively called aroids. There are many familiar outdoor and indoor plants that belong to this group, including calla lily, Caladium, peace lily, Colocasia, Alocasia, Philodendron, and pothos. This plant is found wild in the woodlands of Japan, and it is closely related to Jack-in-the-Pulpit (Arisaema triphyllum), a wildflower that is familiar to many, especially if you have roots in eastern Canada or the US, where it is found in the wild. In fact, the Japanese cobra lily can be described as a Jack-in-the-Pulpit with a uniquely “Japanese” look.
I first encountered this plant as a boy shopping the Collector’s Corner in the Perennial section at Hole’s (around the year 2003). There it was sold under the name “Dragonroot”, and my mother pointed it out to me. It was a cool name for a cool flower – right up my alley. The flowers of a cobra lily – as in all aroids – are really an inflorescence made up of two main parts (but I call the whole thing a flower for the sake of simplicity). A hooded bract called the spathe (the “pulpit”) surrounds a central club called the spadix (“Jack”) which houses the actual tiny flowers. On the Japanese cobra lily, the spathe is a dark black-purple colour, with a green and white striped interior; the spadix looks like a white mushroom inside. It’s serpentine, elegant, and absolutely otherworldly.
The flower unfurls in late spring together with the leaves; each plant produces two of the latter, which are separated into 5 leaflets. On some plants, each leaflet has a central silvery stripe. Overall, it’s a handsome plant, even when not in bloom, although it will go dormant in the heat of summer once flowering is finished. One unfortunate characteristic is that the tubers, unlike most Arisaema, do not form offsets, so the only way this precious plant can reproduce is from seed, and at least two plants are needed for that to happen. If it does, red berries will form after the blooms wither on the pollinated plant. Seeds that germinate will take 3-5 years to bloom, and all of this ensures that this will remain a collector plant.
If you have a shady spot in the yard for this shady
character, it will surely be a conversation piece that will enchant visitors to
your garden. Plant the tuber 4-6 inches deep to help ensure winter survival,
and I encourage mulching for winter as well (although I never do). The soil
should be loose, fertile, moist, and well-drained. This plant will not tolerate
heavy clay soil or dry soil. I love Sea Soil or Annelida Superworm Soil for
enriching garden soil and improving the structure.