My September 15, 2023 blog post “Mystery Plant Quiz: What Is It?!” showed photos of a mystery plant that I discovered sharing a pot with one of our fuchsias. The new plant was so unfamiliar to me that the post became a Mystery Plant Quiz. Readers of Under the Solano Sun were invited to guess the plant's correct identity off the top of their heads and write their answer via the blog post's Comment link. Winners were to be celebrated in this follow-up post.

The mystery plant is Psilotum nudum, aka “whisk fern” because bunched stems can be used like a small broom. No one identified it correctly, but hats off to Karen Metz, whose guess of a Rhipsalis cactus was excellent. Only the jointed stems of Rhipsalis differentiate them clearly from the Mystery Plant photos in the “What Is It?!” post. Perhaps this similar appearance arose from convergent evolution. The two plants occupy the same understory niche in tropical forests.

When I first saw the whisk fern, I thought that this weirdly basic plant with unjointed stems and no leaves, flowers, or fruit must be something very ancient. Indeed, whisk ferns are part of “ferns and allies,” early vascular plants that originated at least 380 million years ago. Whisk ferns are native to tropical and warm temperate regions nearly worldwide. A Florida horticulturalist friend recognized the Mystery Plant photo immediately, and I was thrilled to find spectacular specimens in the Foster Botanical Garden in Honolulu. For more information about these unique plants, please see “The Simplest Terrestrial Plant on Earth: Whisk Fern,” to be published in the January 2024 issue of the UCCE Master Gardeners of Solano County newsletter, Seeds for Thought.

Since whisk ferns are not native to California, the real mystery is: how did one get into the fuchsia pot in mySuisun City back yard? Internet research revealed that whisk ferns can be greenhouse weeds. I purchased the fuchsia from the San Francisco Botanical Garden over a decade ago. Could the mystery plant have germinated from a spore that had long lain dormant in the soil around the fuchsia? I am grateful to Victoria Stewart, Plant Records Manager of the Gardens of Golden Gate Park, for the answer: yes. Her colleagues report that whisk fern “did pop up every now and again as something weedy in the nursery.” 

Whisk fern and fuchsia sharing a pot, April 2023 

(Photo credit: Patricia Matteson)