Catnip is freely branched, several-stemmed perennial with several stems arising from 30-100 cm high from a taproot. The branches that are present turn upward and follow fairly closely to the main stem. The stem and leaves are covered with numerous fine, spreading and fairly short hairs that are white or gray in color. All the leaves are found on the stems, and these are only slightly reduced upwards on the stem. The leaf blades are triangular-ovate in outline with slightly heart-shaped bases, or the leaf bases may be abruptly squared off to the petiole. They measure from 2-7 cm long and 1.5-5 cm long. The petioles are up to half the length of the blade while the margins are ringed with coarse, rounded teeth. The inflorescence is a short, dense and consists of several verticillasters arising from the upper axils. This terminal spike is roughly 2-8 cm long and from 1.5-2.5 cm wide. The calyx, which measures from 5-7 mm long, is tubular with 5 fairly regular teeth which are long, thin and with pointed tips. The calyx teeth are shorter than the tube. The whitish corolla is commonly spotted with red or purple marks and is less than twice as long as the calyx. The upper lip of the corolla is hooded but cleft at its middle, while the large lower lip is sharply reflexed downwards at up to a ninety degree angle from the tube. The wide central lobe of the lower lip has fairly large, irregularly rounded teeth around its margin.
Catnip, a weedy species, may be found in disturbed areas near roads, waste areas, open woods, and along streambanks. It may also be found in fairly undisturbed moist habitats.
Catnip, a native of Eurasia, is now naturalized across much of North America. In the Pacific Northwest, it is more common west of the Cascades, but may also be found in disturbed areas east of the mountains.