A visit to Prairie Alvar on Cape Croker

Neyaashiinigmiing prairie
Alvar grassland at Cape Croker

This past Saturday I had a chance to visit an extraordinary place: the alvar grassland on the shore of Georgian Bay near Cape Croker. The trip was organized by the Field Botanists of Ontario and led by Jarmo Jalava and Tony Chegahno.

The beauty of the place was both breathtaking and subtle. Breathtaking, because the alvar lies under the towering limestone cliffs of the Niagara Escapment and is bounded on two sides by the rocky shores of Georgian Bay. Subtle, because a flat expanse of grass, dominated by poverty oat grass (Danthonia spicata), over which dance the flowers of the common weeds, white sweet clover and Queen Anne’s lace, is going to look a lot like, well, like any old field. It is only when Tony and Jarmo directed me to really look at what was growing did I understand that this is a splendid example of native grassland such as can be found nowhere else in the province.

Invasive Queen Anne’s lace and white sweet clover are a problem, but their presence grew less as we moved away from the road and deeper into the alvar. Both these weeds are being managed on the alvar by hand-pulling and the areas which have been weeded for two years in a row have these weeds much reduced. The site is over 300 acres and neither weed is easy to pull.

Especially near the road, the non-native Canada blue grass is a co-dominant and reflects a history of grazing cows on the land. Elsewherely, the alvar presented us with a sweeping mosaic of native grasses, with golden patches of the beautifully airy tufted hair grass (Deschampsia cespitosa) showing where minute changes in topography allow water to pool on the surface late in the spring. Large stretches of the alvar are dominated by northern dropseed (Sporobolus heterolepis), one of the prettiest of all our native grasses, and one which is very rare everywhere else in southern Ontario. As we drew closer to the shore, we saw more little bluestem (Schizachrium scoparium), easily recognized because the harsh growing conditions of the alvar produce an especially strong characteristic purple-blue tone in the stems. Not all the grassy plants we saw are true grasses: sedges, rushes, and spike-rushes intermingle. The alvar specialist Crawe’s sedge (Carex crawei) is abundant; it had flowered in May and the tips of its stiff leaves were turning gold.

The list of native species we saw would interest any field botanist, but I am not going to reproduce it here. I simply must show you the Kalm’s St John’swort, though. A Great Lakes indigene, it is growing in abundance along the shoreline. I last saw Kalm St. Johnswort a week earlier, when we were coming back from Pelee Island. We had stopped in a newly-reconstructed En Route gas station, and there, in a newly installed native plant garden, among the daylilies and the Clethra, were switch grass and Kalm’s St. John’swort. Sometimes even gas station landscaping can get it partially right.

Hypericum kalmianum
Kalm's St John'swort.

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Trish Murphy

Artist: botanical, still life, and natural history illustration. Garden designer: native plants and naturalistic gardens