I've forgotten what this is.
Kind of looks like an aquatic plant with the common name "horsetail". Do you have a pond?
I agree with Growin. That is the proper name for Rough Horsetail
I believe it is horsetail. It grows here on the riverbank quite high above the usual water level.
Ditto to the above ID as Equisetum. There are many species from little dwarfs, under a foot high to rather large ones. Nothing like the giants that grew when dinosaurs roamed the earth, though. Still, an interesting plant. They can be invasive in damp situations, so I would keep it in its container.
Thanks, all. Yes, Equisetum hymale. Someone gave it to me and I've kept it in the container because I thought it could be invasive. Quite a striking plant under the right circumstances.