Field Guide
This compelling moonwort lives in one of the most interesting locations in Canada
Waterton Grapefern, a compelling moonwort, lives in one of the most interesting places in Canada
If you are a regular reader of this department, you likely will have noted a tendency toward rarity in the plants we feature. Like many plant-people, and naturalists everywhere, at Field Guide we find the more scarce the species, the more captivating the find. By that criterion alone, few plants would be more satisfying to find than our subject this issue: Botrychium x watertonense, the elusive Waterton grapefern.
Hiding in the soil below the surface, awaiting the perfect moment to bust out, this rare moonwort is small and inconspicuous: it spends most of its life below ground supported by mycorrhizal fungi. It is remarkable how little is known about its unseen behaviours. When it does erupt in early summer, in fescue grassland meadows and in clearings among lodgepole pine, it is not much to behold: a few centimetres high, drab green with brown sporangia, this perennial blends with the carpet of leaves, needles and other humus, often completely covered by it. It has to be sought out. That is, if it appears at all: the plant will often skip a year altogether.
The mysterious nature of the moonwort has led through history to many legends and superstitions. Alchemists in their heyday claimed to be able to extract silver from mercury using moonwort. In the 16th century, some said it could melt the shoes off a horse or dissolve a lock—if used in moonlight. In the 1700s, early practitioners of the “medick science” believed moonwort could immediately heal fresh wounds, though only if picked by moonlight.
The pteridologist (student of ferns) W.H. Wagner — a renowned U.S. botanist who fittingly went by his middle name, Herb — identified the Waterton grapefern in 1984. It was also referred to as plains grapefern, prairie moonwort and, oddly, prairie dunewort. A lifelong devotee of the moonwort, Wagner recognized the unique qualities that characterize the B. x watertonense: a hybrid of the Western moonwort (B. hesperium) and its “peculiar” cousin (B. paradoxum), its wide sterile blade has spore clusters along the edge, not on a separate fruiting stalk.
The plant has an interesting family tree: it is a member of the Ophioglossum genus, which loosely translates as adder’s tongue. They are of interest because the modest ferns in this genus are believed to have more chromosomes than any other species (some as high as 1,262 versus a paltry 46 in humans). After 400 million years, these ancient ferns have accumulated a lot of useless chromosomes, “junk DNA,” say the experts.
This deep history helps explain why Waterton grapefern grows in only one place in the world: on the western border lands of Montana and Alberta in and around Canada’s Waterton National Park, about 130 km southwest of Lethbridge. (Way back in 1932, the Canadian park was partnered with its equivalent on the southern side of the international border to form Waterton-glacier International Peace Park, the first of its kind.) It is a rarefied spot, boasting extraordinary biodiversity amid unusual geography. As a result of long-ago plate tectonics, here the eastern slope of the Rocky Mountains descends almost directly to prairie, without transitional foothills. The odd topography is punctuated by a series of very deep, long and crystalline lakes, including Upper Waterton Lake, at 150 metres the deepest in the Canadian Rockies. On the U.S. side is a rare triple divide, a continental hydrological apex. Here are the headwaters of streams and rivers: some flow south from this post and eventually feed into the Mississippi River and on to the Gulf of Mexico and the Atlantic Ocean; others flow north to the South Saskatchewan River all the way (via Lake Winnipeg) to Hudson Bay; while still others flow west to the Columbia River and ultimately the Pacific Ocean. The run-off from a local downpour will end up in three separate oceans that span the entire planet.
The living world here is a wonderfully varied mash-up of habitats, from prairie grasslands and deciduous and coniferous forests ascending to alpine tundra and high meadows. The 500-square-kilometre park, a UNESCO biosphere reserve since 1979, is a plant community and a complex ecosystem that does not appear anywhere else. What a fitting place for our featured plant, an ancient and evolved rarity, a local expression of one of the oldest and most dominant plant types, nurtured in a unique local biosphere shaped by prehistoric forces.