Wednesday 28 October 2020

Blue Sedge (Carex flacca) and Railways

Back in May, Will Van Hemessen mentioned to me that he has observed Blue Sedge (Carex flacca), a non-native sedge, in two locations in Ontario: Kelly Stanton ESA in London, and Fletcher Creek Ecological Preserve in Puslinch, near Cambridge.

Blue Sedge (Carex flacca) from Kelly Stanton, May 2020

Blue Sedge from Fletcher Creek, July 2019

Will noted that, interestingly, the same railway, the Canadian Pacific Railway (CPR) passes right beside the both of them. CP lines are indicated on the map in red.  Adventive (non-native and not yet well established) plants are well known to show up along railways, carried there by the trains.

Looking at sightings on iNaturalist, you would see that there are also sightings of this sedge in the vicinity of Puslinch, as well as in the Peterborough area, near Douro. While the railways do not directly run beside where these observations were made, they are close enough to raise an eyebrow. The species has also been recorded at the Forks of the Credit in Caledon, which has a railway running through it (The Orangeville-Brampton Railway, connected to the CPR) Also on iNat, there is an observation in Sherbrooke, Quebec, and sure enough, the same railway passes by there!

Note: Observations from Vermont and Connecticut are misidentifications

I had seen a couple observations of Blue Sedge in Vermont as well, and got a little excited because the CPR passes through that area too, but upon closer inspection, the sightings turned out to be what looked like Twisted Sedge (Carex torta) (one to keep an eye out for in Ontario by the way!)

Also on iNat you can see there are a few observations in the Grey/Bruce area. According to the Canadian Railway Atlas, where I got the maps, there are currently no railways in that region of Ontario. However, I have been informed that historically, the CPR ran into that region. Apparently, the observations shown on the map are quite close to former CP lines!

There are a few observations of the species on Nova Scotia as well. While again currently the CPR doesn't seem to run out there, apparently it historically did. Based off satellite maps, I can tell that these sightings, while not directly adjacent to railways, they have a similar proximity to some of the sightings in Ontario.

According to the Flora of North America, there are also records of the species in Michigan and New York. I can also find resources that say it occurs in Ohio. The CPR likely doesn't have anything to do with those records (other than maybe the first Michigan collection of Blue Sedge in Wayne County in 1896, near Detroit). There aren't any legit iNat observations for the USA of Blue Sedge, so its hard to see exactly where these records are, but based off county maps, there are definitely railways running through each of the areas, so it is very possible they are close in proximity.

Interestingly, the Canadian National Railway (CNR), which is indicated by blue on the maps, also may have an influence on Blue Sedge distribution. The CNR happens to run right beside Kelly Stanton ESA, where there is Blue Sedge, and had also historically run up into Grey-Bruce. I know that Blue Sedge has also been found in the floodplains of the Nith River near Paris, and low and behold, the CNR runs right through that area! There is also an observation of Blue Sedge in Halifax just across the river from a CNR line.

So is there a correlation between the CPR, and CNR, and Blue Sedge, at least in Ontario and the surrounding area? Maybe. It might be interesting to visit areas along these rail lines, and see if Blue Sedge can be turned up! It is a fairly distinctive sedge, especially when mature, so it should stick out!