Vigorous, spreading members of the mint family, with aromatic foliage. With the exception of catnip (N. cataria), these plants are valuable for their spikes of two-lipped blue or blue-violet (or sometimes pink, white, or yellow) flowers. As soon as blossoms fade, shear plants back by half, or cut faded flower stems to the ground to encourage rebloom. (Most species seed freely and can become invasive if spent flowers are not removed.) Plants make attractive, informal low hedges or edgings. Deer don't usually eat them.
In winter or early spring, cut out last year's growth to make way for new stems. At that time, you can also divide clumps for increase, though it's easy to start new plants from cuttings (take them before flower buds form). When buying named selections, be sure to obtain cutting-grown plants; seedlings vary in flower color and habit. Flowering is spotty in the Tropical South. Provide good drainage.
N. 'Blue Dragon'. Zones US, MS, LS, CS; USDA 6-9. Named for the dragonlike appearance of individual flowers, this bright blue-violet selection grows upright, unlike others, reaching 2 ft. tall and wide.
N. cataria. CATNIP. Zones US, MS, LS; USDA 6-8. From the Mediterranean and western Asia. To 23 ft. high and wide, with downy, heart-shaped, tooth-edged gray-green leaves. Spikes of small (14- to 12-in.) whitish or pinkish flowers in late spring, early summer. Not very ornamental but worthy of a place in the herb garden. Grows easily in light soil and self-sows readily. Common name refers to stimulant effect on cats. Their susceptibility to the herb varies, though: Some felines fall into a rapturous frenzy, rolling wildly on the plant, but others ignore it. If necessary, protect crown of plant with an inverted wire basket; stems will grow through. The same tactic also helps preserve potted plants grown outdoors and brought indoors occasionally for cats to enjoy. You can also sprinkle dried leaves over your cat's food or use them to stuff cloth toys. Some people use catnip to flavor tea. 'Citriodora' has lemon-scented foliage.
N. 'Dropmore'. Zones US, MS, LS, CS; USDA 6-9. Grows to 1 ft. high and 3 ft. wide, can bloom from late spring to fall with lavender-blue flowers.
N.x faassenii. CATMINT. Zones US, MS, LS; USDA 6-8. Sterile hybrid of N. racemosa and a European species; often sold as N. mussinii. Soft, silvery gray-green, spreading mound grows to 1 ft. high, 1122 ft. wide. Scallop-edged, heart-shaped leaves to 1 in. long. Attractive to some cats, who enjoy nibbling on and rolling in plantings; insert short, blunt-tipped sticks in the ground among the leaves to discourage cats and prevent destruction. Loose, lax spikes of 12-in. lavender-blue flowers in late spring, early summer. Set plants 11 ft. apart for ground cover. 'Limelight' grows only 10 in. tall and 2 ft. wide, the lime-green foliage makes an energetic backdrop for the blue-lavender flowers. Less robust than other selections. 'Kit Cat' (Zones US, MS; USDA 6-7) is shorter, reaching 15 in. with blue-purple flowers on gray-green foliage. 'Select Blue' has darker flowers than the species; 'Snowflake' has pure white blooms. 'Cats Meow' forms a dense, rounded mound with sky-blue flowers.
N. grandiflora. GIANT CATMINT. Zones US, MS, LS, CS; USDA 6-9. Native to Europe, Caucasus. Open clump to 24 ft. tall, 35 ft. wide. Gray-green, hairless or sparsely hairy, scallop-edged, egg-shaped leaves to 4 in. long. Violet-blue, 34-in. flowers in late spring, early summer. 'Bramdean' has lavender-blue blossoms with purple calyxes; 'Dawn to Dusk' has lilac-pink blooms, smoky violet calyxes. 'Wild Cat' has purplish red calyxes. Calyxes of all these selections persist after flowers have faded.
N. nervosa. Zones US, MS, LS, CS; USDA 6-9. Native to Kashmir. Grows to 12 ft. tall but may spread into a mound 12 ft. wide. Bright green, conspicuously veined, tooth-edged leaves are lance shaped, 24 in. long. Brilliant violet-blue (rarely yellow), 12-in. flowers bloom from midsummer to early fall. Afternoon shade is helpful. 'Blue Carpet' and 'Pink Cat' grow to 1 ft.
N. 'Purple Haze'. Zones US, MS, LS, CS; USDA 6-9. At only 10 in. tall, this vigorous selection grows into a mound 4 ft. across. The showy flowers are held in spikes.
N. racemosa (N. mussinii). PERSIAN CATMINT. Zones US, MS, LS; USDA 6-8. Native to the Caucasus, Turkey, Iran. Sprawling plant grows from 6 in. to 1 ft. tall and about 2 ft. or more wide. Roundish, scallop-edged, 12- to 1 14-in.-long leaves range in color from medium green to gray-green; they are covered with fine hairs. The typical form produces 13-in.-long lavender flowers for a short period in mid-summer; may rebloom if sheared. Reseeds wildly. Inferior to its hybrid N.xfaassenii, but there are several worthwhile selections that are more compact than the species and bloom over a longer period. 'Blue Ice' has dense, gray-green foliage and pale blue flowers that fade to near-white. 'Superba' has a dense, matlike habit and gray-green leaves that are smaller than those of the species; it bears lavender-blue blossoms from spring through fall. Violet-blue flowers of 'Walker's Low' grows 23 ft. tall and has vivid lavender-blue flowers.
N. sibirica (N. macrantha). SIBERIAN CATNIP. Zones US, MS, LS; USDA 6-8. Native to Siberia. Sturdy, upright habit to 23 ft. tall and 1122 ft. wide. Dark green, oblong to lance-shaped, 3-in.-long leaves are softly hairy beneath. Spikes of large (112-in.) violet-blue blossoms appear for about a month, beginning in early summer. 'Souvenir d'Andr Chaudron' ('Blue Beauty') is similar but grows only 1 ft. high and blooms for a longer period, with season extending into late summer.
N. 'Six Hills Giant'. Zones US, MS, LS; USDA 6-8. Possibly a hybrid of N. xfaassenii and similar to itbut grows taller (reaches 212 3 ft. high and as wide), has greener foliage, and bears deeper blue flowers. More tolerant of damp climates than other nepetas.