The Collaborative International Dictionary
mad-dog skullcap \mad-dog skullcap\, mad-dog weed \mad-dog weed\n. (Bot.) An American mint ( Scutellaria lateriflora) that yields a resinous exudate used esp. formerly as an antispasmodic.
Syn: blue pimpernel, blue skullcap, Scutellaria lateriflora.
Wikipedia
Scutellaria lateriflora, known commonly as blue skullcap, mad dog skullcap, and side-flowering skullcap, is a hardy perennial herb of the mint family, Lamiaceae, native to North America.
It has an upright habit, growing 60 to 80 centimeters in maximum height. It is a wetland-loving species and grows near marshes, meadows, and other wet habitat. The blue flowers are just under a centimeter long. Most of the flowers do not appear at the top of the main stem, but are produced along the length of side branches that grow from the leaf axils.