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Leathery Moonwort

I love finding new populations of PEI’s rarest plants, and ferns are my favourite plant group. So, you can imagine how excited I was to find a new location for one of our Island’s rarest ferns – Leathery Moonwort! (Sceptridium multifidum, which I know by its older name of Botrychium multifidum).


Leathery Moonwort (Sceptridium multifidum) on PEI.

Ferns are an ancient group of plants, far older than conifers, flowering plants, or dinosaurs. They appear in the fossil record some 360 million years ago, making them older than even our red Island sandstone. PEI has more than 30 species of ferns, found in habitats ranging from rich old growth forest to highly disturbed old fields and roadsides. I find fern ID guides are needlessly complicated for our local species and have written a key to help non-botanists identify some of our more common ferns (you can find it here: https://www.pei-untamed.com/post/kate-s-key-to-some-common-ferns-of-pei).


Leathery Moonwort is one of the Grape Ferns, named for the resemblance of their spore-bearing structures – seen at the top of the plant – to clusters of grapes. Each fern can produce thousands of tiny spores which are dispersed by wind. Unlike the seeds of flowering plants, fern spores don’t grow into replicas of the parents. Instead, they germinate into haploid gametophytes: a stage that has only one set of chromosomes rather than two and is very unlike the parent plant. Leathery Moonwort spores must be underground and in complete darkness to germinate; the germination and survival of the resulting gametophytes requires partnerships with mycorrhizal fungi. Without fungi, there would be no Leathery Moonwort.


The gametophytes mature and release gametes (male and female cells, analogous to sperm and eggs). Water unites the cells, fertilization occurs, and a diploid sporophyte – what we recognize as a fern – germinates. In the case of Leathery Moonwort, sporophytes can live underground for several years before pushing their way to the surface and growing into a beautiful, mature fern. While underground, they are totally dependant on mycorrhizal fungi for nutrition.


Leathery Moonwort is a long-lived fern (some individuals are known to be at least 100 years old) and is rare throughout much of its range. Before this year, I’d only found it on two sites here on PEI: one old growth forest and one stable sand dune. I’ve been doing some work on our offshore islands this summer and was intrigued when I spotted old growth forest indicator species from the shore at one of these sites. Last week, I returned to investigate further and within minutes found a small and previously unknown population of Leathery Moonwort.


Although we think of our Island as heavily settled with little wilderness, there are still important wild spaces and species to be discovered. That’s one of my favourite things about PEI untamed!

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