Thanks again to marcella2@Flickr for sharing a photograph (original image | BPotD Flickr Group Pool). The last time a photograph from marcella2@Flickr was featured on BPotD, over three dozen images of plants were available by clicking on the marcella2@Flickr link – now there's over five dozen, so you might like to revisit them.
I should first of all note that I've changed the name of the plant posted by marcella2 from Sparganium ramosum to the catch-all Sparganium erectum (a number of Sparganium are listed as being synonymous to Sparganium erectum). I'm following the nomenclature suggested by Missouri Botanical Garden's TROPICOS database, but with reservation. In a conversation with Richard Lansdown ten days ago or so, Richard expressed the opinion that many of the less-examined plants sharing the same name in both Europe and North America are actually quite different from one another. Even the Flora of North America expresses reservation about the nomenclature within this genus, because the last work done on it (in the mid 1980s) did not contain detailed studies of the species across their complete ranges. A grain of salt is required, it seems.
I've an inexplicable soft spot for plants in the genus Sparganium, despite the fact that some have been declared a noxious weed. It may be that the soft spot stems from the exotic appearance – exotic, at least, to someone first learning plants through observing the native plants of Manitoba. I still find them interesting, and I know if I encountered some similar to these, I'd spent quite a bit of time photographing them.
Botany resource link: The northernmost botanical garden in the world, Tromsø Botanical Garden at nearly 70° N in Norway. Tromsø BG has a growing season from late May to mid-October, thanks to the effect of the Gulf Stream.