St Johns Wart Question

My friend undoubtedly made a mistake in identifying my plant from the beach.
Based on the picture and information in the attached link, my plant is Penny
Wort, and based on the article, it will live in water floating (I think).
Sorry to take up your time with the wrong name, etc., but I'm glad that I
was able to figure this one out.

http://www.npwrc.usgs.gov/resource/1...8/hydrumbe.htm


"Mud" wrote in message
. com...
I pulled up a few plants from the sand at the beach condo last week and
planted it in some sand in a cup. It appeared that some of this same plant
was growing at a distance in some of the stream water on the properties. A
friend tells me that it is St. John's Wart. I'm not sure myself. My
question is... if it is one of the wart plants, will it grow in my small
pond as a floater, spreading to cover the top, or does it have to be in the
ground? TIA!