Catnip (Nepeta cataria)
This is probably your cat’s favorite herb, but it seems to have almost the same intensely euphoric effect on little white butterflies, to judge by the swirling masses of them that were visiting this plant. It was blooming in late July at the edge of an overgrown gravel drive in Scott Township. A tisane can be made from the leaves, but your cat will probably drink it before you get a chance at it.
Nepeta cataria is the only species commonly found in the wild around here. In Gray, the genus Glechoma is also included in Nepeta.
NÉPETA L. CAT MINT. Calyx tubular, often incurved. Corolla dilated in the throat; the upper lip erect, rather concave, notched or 2-cleft ; the lower 3-cleft, the middle lobe largest, either 2-lobed or entire. —Perennial herbs. (The Latin name, thought to be derived from Nepete, an Etruscan city.)
§ 1. CATARIA [Tourn.] Reiohenb. Cymose clusters rather dense and many-flowered, forming interrupted spikes or racemes; upper floral leaves small and bract-like.
N. catària L. (catnip.) Downy, erect, branched; leaves heart-shaped, oblong, deeply crenate, whitish-downy underneath; corolla whitish, dotted with purple. — Near dwellings; a common weed. July-Sept. (Nat. from Eu.)
In his Field Book of American Wild Flowers, F. Schuyler Mathews becomes uncharacteristically personal in describing this plant:
Nepeta cataria. An exceedingly common weed to which many of the animals of the tribe Felis are greatly attached. A favorite Manx cat of mine would walk a mile every other day or so, from my Campton studio to a spot where it grew in plenty, notwithstanding the way was through the woods and over a hill of no small difficulty! The stem is densely downy as well as the deeply round-toothed leaves, and both are sage green in color. The pale lilac or lilac-white and spotted flowers are also downy, and gathered in small terminal clusters, which are rarely 4 inches long. Leaves strongly aromatic. 2-3 feet high. Common everywhere. Naturalized from Europe.
In Wild Flowers East of the Rockies (1910), Chester Albert Reed gives us a little more of the lore of Catnip:
CATNIP (Nepeta cataria) (EUROPEAN) is a very common mint, introduced from Europe, the aromatic foliage of which has a very peculiar attraction for all members of the feline race. It apparently has an intoxicating effect upon them; after eating the leaves they will roll about on them for a long time. It also formerly was used for making Catnip tea, a one-time remedy for most of the ills of childhood. The plant has a stout, square hollow stem from 2 to 3 feet tall and is downy, as are the sage green, toothed leaves. The lilac-white flowers are clustered on peduncles from the axils of the leaves. Catnip is common throughout our range.