Cotton Grass

2021 August 8

On July 25, 2021, we were up near Eagle Harbor, at the stamp sands. We went for a stroll at the wetland area at the edge of the stamp sand deposit[1], and noticed that the dominant water plant seemed to be these grasslike plants with little cottony tufts at the tips of their stalks.


These were new to us, so I wanted to figure out what they were. Even though I didn’t have one of my regular cameras with me, I was able to get some OK pictures with my phone.


The gray sandy material is stamp sand, which is crushed basalt with about 0.25% copper still in it. While a lot of other plants seem to have difficulty growing directly in stamp sand, these don’t seem to be much bothered by it.


We picked a few of the cottony seedheads to take home, for some better photographs with a camera that actually had some close-focus capability.


The fibers look a lot like cotton, and are about half an inch long.


This is one of the species of Cotton Grass, genus Eriophorum. I’ve gotten used to plants and animals that aren’t common here because we are too far north, but in this case, we don’t normally see them because we are too far south. Cotton grasses are mostly tundra plants, living way up north where the trees don’t grow. They mainly grow in acidic bogs and wetlands, and apparently don’t require much in the way of organic matter in the soil, seeing as how these were basically growing in bare sand.

Cotton grasses are actually sedges, family Cyperaceae which are not quite grass, but are closely related to grasses. Sedges mostly like soggy areas, so if you see something grasslike growing in a wet environment, it is probably a sedge and not a grass.

The cottony seed heads can be used similarly to actual cotton, although the fibers are shorter and the seed heads are smaller, which would make it more tedious to pick and probably a bit harder to spin into thread or string. Still, it is interesting to think that, if things had developed a bit differently so that these plants had somewhat bigger seed heads, arctic countries like Canada might have actually been major players in cotton production.

[1] I’ve mentioned this before, but stamp sand is the residue left over after extracting copper from the local copper mines, and was mostly made between about 1860 and 1960. The local copper ore consisted of copper metal pieces embedded in basalt or conglomerate, and the most effective way to get it out was to use stamp mills (basically giant steam-driven hammers) to smash the rocks until the copper pieces broke free. This then went to jigs that separated the dense copper from the low-density rock. The rock, which was now the size of sand, was dumped on flat areas and beaches to dispose of it. The sand isn’t particularly toxic (aside from the 0.25% copper, it doesn’t contain much in the way of heavy metals), but it is just sand that doesn’t hold moisture or have any organic matter in it. The copper content mainly suppresses seedling germination, and the dark color of the sand means that it gets hot in the sun, so it tends to cook young plants. But once a tree or shrub gets established, it can grow in the sand OK. The upshot is that the fields of stamp sands are basically barren, with nothing growing on them unless an effort is made to reclaim them.

4 Responses
  1. Steve Plumb permalink
    August 10, 2021

    Lots of Cotton Grass here in Maine, grows in boggy areas. A favorite of mine.
    What piqued my interest in this post was your reference to the stamp sands which I’d never heard of. A quick search illuminated the subject well. Perhaps they aren’t a serious problem in your location but reading about the “Gay Stamp Sands” reveals that coastal disposal sites on the Upper Peninsula are a big problem. 20 million tons washed out along the shore and into the lake in the town of Gay!

  2. August 10, 2021

    Steve: Yes, I probably should have mentioned that. The beach deposits like the one at Gay are much more of a problem than the inland deposit at Eagle Harbor. The big issue seems to be a mechanical problem, the sand fills in the crevices in the rocky bottom that the lake trout like to spawn in, and the grains themselves are sharp and hard on any eggs they do lay. And the copper in the sand is just toxic enough that aquatic life doesn’t really take hold in it, which just keeps it from getting better over time.

    Stamp sand isn’t anywhere near the same level of toxicity as other types of mining tailings that actively release heavy metals like lead and mercury and arsenic, but it is not really great stuff for the wildlife even so.

  3. Lyle L permalink
    August 18, 2021

    I’ve also seen this grass at the Centennial Mine north of Calumet

  4. August 19, 2021

    Lyle: That’s interesting, if I have the right spot then it looks like there is a lot of old copper-mining rock around there, too, and the general area looks like not much else grows there. If the cotton grass is really more copper-tolerant than other plants, maybe it should be being used more in the remediation projects.

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