Essential plants for any herb garden.
This giant catmint, Souvenir d’André Chaudron, is a cool splash of color in the herb garden.
I will always fondly remember Emma Wakefield and her herb garden. In the late 1960s, when I was high-school age, she introduced me to herbs and the folklore associated with them. This retired schoolteacher, now deceased, was one of the leading herb growers in Oregon. Seldom did I return home from a visit to her garden without an herb division wrapped up in newspaper with the name scribbled on the corner.
That’s how catnip (Nepeta cataria) first came into my life. I planted Emma’s gift in my garden, then went about my weeding chores. Suddenly an alarming commotion of thrashing noises and quaking bushes erupted. Peering over the top of the bee balm, I discovered our cat, Squinklock, usually an ill-tempered brute, curled blissfully around the base of the catnip plant. She looked up at me through slightly closed eyelids, a euphoric expression on her face, then, without warning, started shredding the plant. When I rebuked her for wanton destruction, she bolted, attacking unknown imaginary prey and one unfortunate sleeping dog.
I recalled the couplets that Emma had recited to me while wrapping up the catnip: “If you set it, the cats will eat it. If you sow it, the cats don’t know it” (Philip Miller, 1754). In other words, foraging cats are much less likely to attack self-sown plants than plants newly set out. Today, we know that the bruised leaves of a newly transplanted catnip plant release nepetalactone, a component of the essential oil that mimics a cat’s sexual pheromones. Catnip thus acts as an aphrodisiac, which may explain the bizarre ways in which cats react to catnip. Now I wonder, did the cat attack the dog out of spite, or was it a crime of mistargeted passion?
Catnip and its effect on cats have been well documented. A thirteenth-century German manuscript refers to catnip as Kattesminte, or catmint. The genus name Nepeta is believed to be derived from the city of Nepi (called Nepete by the Etruscans) in Tuscany, Italy, where catnip once grew in great profusion. Although only twenty or so species and cultivars are available in current catalogs, the genus comprises about 250 species. All originated in temperate areas of Europe, Asia, and Africa and have naturalized elsewhere. In North America, catnip has spread to the point of weediness.
Catnip nonetheless remains an extremely well-known and popular aromatic perennial herb. The common name catnip is usually limited to N. cataria while the term catmint refers to practically all the other species. Members of the mint family (Lamiaceae), nepetas have the characteristic square stem with opposite, aromatic gray or green leaves that are usually toothed. The individual flowers are generally small, 1/4 to 1/2 inch long, and two-lipped; the calyx tube of fifteen ribs is characteristic of the genus. The flowers are nearly all various shades of blue to white and are found in clusters either at the stem tips or in the leaf axils. Those of N. sibirica, N. grandiflora, N. subsessilis, and N. yunnanensis are rich deep blue to violet.
Nepetas are often found in the wild in sunny, dry locations, particularly in chalky or gravelly soils. They are drought resistant and require far less moisture than their mint relatives. All prefer well-drained soil; winter wetness can be fatal. Most species tolerate lean soil, although more fertile soils encourage bushiness. All will grow in soil of pH 5 to 7.5.
Many nepetas tend to spread and flop over on their neighbors. Shearing the plants back hard after flowering to about two-thirds their original height not only restores their shapeliness but generates a good rebloom later in the summer. Some species, including N. sibirica and N. nervosa, can be invasive, so I occasionally spade around the plants to curb their vigor. I also leave the spent autumn-flowering stems on the plants over the winter to provide a protective canopy.
I haven’t seen many pest problems. (This may be due to nepetas’ essential oil content. Nepetalactone has been shown to repel insects.) Slugs attack some of the larger green-leaved species in spring, and occasional infestations of cucumber beetles occur in some years. Some gardeners have reported powdery mildew during hot, dry summers, but my nepetas have not been affected.
Propagation is best done by plant division in the spring or fall. I prefer spring to allow divisions to become established well before winter. If you want more than a few large starts, direct-sow seeds outside in the fall; spring sowing may result in erratic germination. Barely cover the seed with soil as light aids germination. In subsequent years, remember the couplets and allow the species to self-sow, and you’ll be rewarded (cursed, some might say) with thousands of seedlings. Catnip seeds may remain viable for as long as five years. Cultivars are not reliably true from seed, so I take softwood cuttings from the base of these plants usually in early spring when they are just emerging. If I forget, I shear my stock plants back hard in June to force them to generate softwood cutting material in July. I stick the cuttings in a sterile rooting mix or coarse sharp sand and water them well. During hot weather, I place the cuttings under a mist system. They root readily in a few weeks.
The best-known species of Nepeta among herb gardeners is catnip. Folklore about it abounds. Because eating dried catnip root was supposed to make gentle people quarrelsome, executioners and hangmen would eat it to ensure the courage necessary to carry out their duty. In fifteenth-century France, catnip was used as a culinary herb for soups and stews, and the young shoots were used in salads. About 1620, catnip was introduced to North America by a Captain John Mason, who considered it one of eleven essential herbs for the fisherman’s garden in Newfoundland. It became a popular everyday tea.
Catnip has long been cultivated for its medicinal properties. It is primarily used as a remedy for colds, fevers, upset stomachs, and in the treatment of children’s complaints such as colic. It acts as a mild sedative and is a common ingredient in herbal sleep pillows. Chewing a leaf reportedly relieves headaches. Today, oil of catnip is used widely in veterinary medicine and as a lure to trap larger wild felines such as bobcats and cougars.
Catnip is an erect, branched plant 3 to 4 feet tall with large, coarsely toothed, heart-shaped leaves. It is easily distinguished from other Nepeta species by its long-stalked leaf that is light green above and frequently white-spotted, crinkled, and downy underneath. The stems are also downy. The fuzziness is what helps catnip tolerate drought. The flowers are small (1/4 inch long) but numerous in dense terminal whorls; the corollas have reddish spots inside. Here in Oregon, catnip blooms from July through September.
Store-bought catnip is far inferior to homegrown. Most commercial catnip is imported and contains 60 to 80 percent stems. To harvest catnip to stuff into mouse toys for my cats or other uses, I cut the upper two-thirds of the plant when the essential oil is at its strongest, just before blooming. I air-dry my swags in a well-ventilated barn, then strip the leaves and flower buds from the stems, which have rather sharp slivers that may injure a cat. In my garden, I can usually get two or three harvests of catnip tops.
If I do not allow catnip plants to go to seed, they remain faithfully perennial; in winter they often have an evergreen base of short, purple-tinged new growth. Plants allowed to reseed seem less winter-hardy and less long-lived than those that I deadhead. However, catnip seed heads make good winter forage for goldfinches and other small birds.
Besides the species, I grow two other forms of catnip, both similar in growth habit. One unnamed form has more ornamental purplish pink flowers. The cultivar N. cataria ‘Citriodora’ has lemon-scented foliage.
I include catnip plants in my herb garden for their historical and medicinal importance, but I relegate them to the back of the border because they have little ornamental value. For beauty, I look to the more refined catmints.
Native to the Caucasus, Persian catmint is a small, mounding plant rarely more than 12 inches tall with aromatic gray-green scalloped leaves. Its 1/2-inch blue flowers are borne in profusion in loose terminal spikes over a long bloom period, from about mid-May through September. Both the species and the numerous cultivars set seed profusely, but seedlings may not come true. Persian catmint may spread to 2 feet wide. It is hardy to Zone 4.
Dropmore is an attractive form with dark blue-violet flowers. Snowflake, with pure white flowers in early summer and a low, spreading habit, would be a good choice for a white theme garden, although seed-grown plants under this name sometimes have pale blue flowers. Superba produces dark blue flowers from April through August. It is also an attractive low, spreading plant. Walker’s Low, a recent introduction from England, has arching stems and rich violet-blue flowers from May through September.
N. racemosa and N. ¥ faassenii are very similar plants. Both are sold under the common name of catmint and are used as a ground cover or in large drifts.
N. ¥ faassenii, which originated at the Botanic Gardens in Copenhagen, Denmark, is a hybrid between N. racemosa and N. nepetella, a species from Europe and North Africa. It is valued for its ornamental gray-green foliage (1 to 2 inches long) and violet-blue flowers. Like Persian catmint, it has a low, mounding growth habit, but it is usually taller, reaching about 2 feet. It is slightly less sprawling with a shorter blooming period, which I extend by constant deadheading and shearing in July to promote August bloom. N. ¥ faassenii can look unkempt and floppy with the weight of the flower spikes, but it is somewhat tidier than Persian catmint and, with the right companions, is an excellent candidate for the hot, dry border. It’s especially well suited for planting with pink roses and peonies. It is hardy to Zone 3, but a combination of winter dampness and biting winds can set it back.
Propagation is by division or cuttings only because it produces sterile seed; if you have seedlings emerging around established plants, you probably are growing N. racemosa.
Six Hills Giant, sometimes sold as N. gigantea, is simply a larger version of N. ¥ faassenii, reaching 2 to 3 feet high and at least 3 feet wide. This English selection has a much-improved form and is a better candidate for the big border with its larger sprays of flower spikes. It has proven much more vigorous, especially in colder, damper climates, but requires good drainage. It has lovely dark blue flowers and will bloom throughout the summer if deadheaded. It may take two years to reach its maximum height.
N. ‘Porzellan’ (‘Porcelain’) is another low-growing hybrid of N. racemosa and N. nepetella. It has lovely, soft porcelain blue flowers from May through September and narrow, aromatic gray leaves.
Pool Bank, recently arrived from England, is an upright cultivar to 3 feet with tall, branching heads of blue corollas and purple calyxes. This good summer bloomer is fast becoming one of my favorites. It is spectacular in a large planting. Be forewarned: in an unscientific test for cat addiction, the aromatic foliage was well received.
This lower-growing catmint is a bushy, showy plant with dense bottlebrush heads of pure blue flowers with white lips and long, narrow, distinctly veined, brilliant green leaves. It blooms from July to September, spreads by underground runners, and may be very late to appear in the spring. Slugs and snails love it. Native to Kashmir, it is hardy to about –15°F. N. connata is similar but has purplish flowers.
This species features long, open spikes bearing large flowers of a deep violet-blue. The corolla tube is straight rather than curved as in other catmint species, which may account for its attractiveness to butterflies and hummingbirds. My specimen is an erect grower to about 3 feet and about half as wide. It is a good plant for the middle of the border and blooms in June and July; however, it has wandering, sometimes invasive roots.
Souvenir d’André Chaudron, also sold as Blue Beauty, is the most popular giant catmint cultivar. It is slightly shorter and stockier than the type, growing to about 21/2 feet tall. It has large terminal sprays of deep lavender-blue flowers and a longer blooming period, starting in May. It is considered a better form to grow in northern climates in full sun. Where summers are hot, give it partial shade. Although it is lovely in bloom, the scent of the foliage when bruised has been described as “fruitily foetid and quite nauseating.”
All the nepetas mentioned thus far are useful planted in large drifts or as edgings along paths, or repeated along the perennial herbaceous border. They pass all the tests for winterhardiness, pest resistance, and long bloom. They can hold a border together, the lovely gray foliage providing contrast and texture while enhancing soft, pastel colors of other plants.
Lately, I find myself gravitating to some of the lesser-known species now becoming available from the Far East and Europe. These new introductions are more ornamental with larger flowers in more intense colors. I think we’ll see much more of these in the future. Here are some of my favorites.
Kashmir nepeta (N. govaniana) is an exception to the rule in more ways than one. It prefers moist, mildly acidic soil in a cool location rather than the open, full-sun site that most nepetas enjoy. I planted mine in partial shade, and it has done superbly, growing to 3 to 4 feet. This lovely, erect, well-branched, hardy (to –15°F) plant further surprises in late summer, when it displays long, open spikes of pale, creamy yellow flowers. The soft, sage green oval leaves are sweetly aromatic but not appealing to cats.
Caucasian nepeta (N. grandiflora) is not seen much in American gardens, but it is quite lovely. It has the typical gray-green aromatic leaves and blooms from May to September with 3/4-inch-long deep violet flowers that are much showier than those of the more familiar species. Its sturdy, nonflopping stems grow erect to 3 feet tall. The cats will leave its strongly pungent leaves alone, but the flowers are appealing to bees.
I brought N. melissifolia, a native of Crete and Greece, back from England several years ago, but few U.S. catalogs list it. This 3-foot bush has proven reliably hardy, and I like it for its large green leaves that are similar to those of lemon balm. It runs a bit but is not overly invasive. In midsummer, it sends up short spikes of 1/2-inch blue flowers spotted with red.
I bought Himalayan catmint (N. clarkei) two years ago from a mail-order nursery, and this recent introduction from Kashmir has become one of my favorites. The first year, my plant reached only 2 feet high, but the following year it was 3 feet tall and nearly 4 feet wide. It is topped with long, full spikes of white-lipped, sky blue flowers from July through September. This plant would be spectacular in a mass planting. Because it is native to the Himalayas, it may not perform as well in a hot climate.
N. tuberosa, native to Portugal, Spain, and Sicily, has heavily felted foliage; in full sun, it takes on a silver color like lamb’s-ear. It is a short-lived perennial in Oregon, with its wet winters. This species needs a free-draining soil. To overwinter, English books suggest digging the tubers up and storing them as you would dahlias. I like the numerous erect, stout flower spikes that are covered with a profusion of small, velvety blue flowers. The flower heads dry exceedingly well, and I’m surprised that dried-flower arrangers haven’t used them more. I also have a dwarf form that is prostrate and slightly creeping. I use it for the front of the border. I find it is slightly more winter-hardy than the upright form. Both set seed sparingly.
N. stewartiana, from Pakistan, is similar to N. sibirica but has slightly smaller flowers and a curved corolla tube. It has the same erect growth habit and long spikes of large, striking violet-blue flowers, only spotted with yellow. It is hardy to Zone 6.
I acquired the seed for Chinese catmint (N. yunnanensis), originally collected on an expedition to China, from a plant society. This species has large green leaves and does well in moist soil in partial shade. It has large, dark blue flowers on short terminal spikes but is unfortunately a favorite of slugs and cucumber beetles.
Japanese catmint (N. subsessilis) is a beautiful species with large green leaves that grows on shaded rocks along streams in Japan. I grow it in moist soil in partial shade. Starting in July, large, terminal, deep blue flowers with maroon splotches open on short spikes. The upright stalks grow about 2 feet tall. This species has proven hardy for our winters. However it, too, is attractive to slugs.
Catnips and catmints are an essential part of my herb garden. They complement the blue-violet flowers of anise hyssop, hyssop, and lavender, and the profuse yellow flowers of phlomis, and their flowers take on a deep, rich tone as the light changes at the end of the day. Hummingbirds become zealots when they discover catmint flower heads. Who knows, one of the new Asian catmints may even put a wrinkle in the aloof demeanor of my Siamese cat.
Andy Van Hevelingen and his family (and cats) have an herb nursery in Newberg, Oregon. He is the author of “Agastaches” (June/July 1994) and a regular contributor to “Round Robin”.
The following companies offer a selection of nepeta plants or seeds by mail order.
Alplains, 32315 Pine Crest Ct., Kiowa, CO 80117. Catalog $1.
Canyon Creek Nursery, 3527 Dry Creek Rd., Oroville, CA 95965. Catalog $2.
Companion Plants, 7247 N. Coolville Ridge Rd., Athens, OH 45701. Catalog $2.
Heronswood Nursery, 7530 288th St. NE, Kingston, WA 98346. Catalog $4.
Sandy Mush Nursery, 316 Surrett Cove Rd., Leicester, NC 28748-9622. Catalog $6.
Well-Sweep Herb Farm, 317 Mt. Bethel Rd., Port Murray, NJ 07865. Catalog $2.
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