Horsetail Mares Tail. (not to be confused with a pond weed that has the same common name) It is not Japanese Knotweed. It is though something you will probably want to get rid of.
yep definitely horsetail. We have lots of it here, so much so that we just have to live with it in most of the areas of the garden which is an acre. It really is very difficult to get rid of. If its in the grass, mowing should keep it at bay. Otherwise just keep pulling it up which does weaken it. If you only have a small area of it, then I would make a huge effort to get rid. there's lots of stuff online that should help. Its like a prehistoric weed! Even comes through tarmac here!
You really need to pull-up, bag and dispose of those shoots now, as they look at the stage they are dispersing spores which can go on to infect other ground.
A trowel in the hand is worth a thousand lost under a bush.
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https://www.allotment-garden.org/gardening-information/weed-control/control-horse-mares-tail-equisetum-arvense/
Agree with polb you have to learn to live with horse tail.