Can you help me with this plant?

Mavis Barnes
by Mavis Barnes
This is a water plant with think stem up to six feet with a fireworks looking burst as the flower. What is it and how do I winter it inside
This is a plant I don't know the name of but it is a water plant with long single stalk and a spiky top that looks like a green Fireworks burst . How do I winter this.?
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