This section is from the book "Who's Who Among The Wild Flowers", by W. I. Beecroft. Also available from Amazon: A Field Guide to Edible Wild Plants.
Pontederia cordata. Pickerel-weed Family. July - Sept.
An erect, stout, fleshy plant 1 - 3 feet high, found in shallow water. Nova Scotia to Ontario, Minnesota and Texas.
Violet-blue, 2-lipped, upper lip 3-lobed, with 2 yellowish spots within; lower lip of 3 spreading lobes; flowers borne on thick spike.
One large leaf shaped like an arrowhead, is borne midway of the flower stalk.

Pickerel-weed.
 
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