What plant is that?

This beautiful flower appears in late spring and summer in moist woods and along the edge of swamps. Its large smooth-edged leaves alternate on the stem. The 1 inch-long, irregular magenta flowers are grouped in narrow spikes reaching an overall height of 2 to 4 feet. Pollinated by large butterflies and moths. Note: this has a different scientific (Latin) name in Newcomb’s Wildflower Guide – check GoBotany before submitting your guess.