Nepeta
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Read about Nepeta in the Standard Cyclopedia of Horticulture
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Nepeta (Latin, perhaps from Nepete, an Etrurian city). Labiatae. This group includes catnip, ground ivy and some other hardy perennial herbs of the easiest culture. Perennial or annual herbs, tall and erect, or dwarf and more or less trailing: lvs. dentate or incised, the floral ones like the rest or reduced to bracts: whorls of fls. crowded in a dense spike, or in a loose cyme, rarely few-fld. and axillary; fls. blue or white, seldom yellow; calyx 15-nerved; corolla somewhat 2-lipped; upper lip straight or erect; lower lip spreading, 3-lobed, with the large center lobe concave; perfect stamens 4. in pairs, the 2 shorter ones in front; ovary 4-parted. The genus is placed near Lopanthus and Dracocephalum, and is characterized as follows: calyx tubular, the mouth straight or oblique, 5-toothed; stamens usually parallel, ascending; anther-cells divergent or divaricate.— About 150 species, mostly in the northern hemisphere outside the Old World tropics. Catnip is a familiar weed near dwellings and barns. Cats are fond of it, and catnip tea is a pungent memory with those who have survived the era of homely simples. The seeds of catnip are still offered. Ground ivy (N. hederacea) also grows wild in America, and a form of it with variegated foliage is cultivated for edging flower-beds or covering banks and stones. It is hardy in light well-drained soils, but sometimes winter-kills in moist soils. It is also used in vases and baskets. N. hederacea is a perennial creeping plant of easy culture in any loose, rich, fairly moist soil in either shade or full sunlight, but to be luxuriant in the open it should have a moist rootage. It is a very rapid grower, and is therefore often troublesome when planted with other low-growing plants. It is very useful as a ground-covering in shrubbery borders and shady places generally, particularly where it can hang over curbs or edgings or where a good sward cannot be secured.
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Nepeta is a genus of about 250 species of flowering plants in the family Lamiaceae. The members of this group are known as catnips or catmints due to its famed liking by cats—nepeta pleasantly stimulates cats' pheromonic receptor. The genus is native to Europe, Asia, and Africa, with the highest species diversity in the Mediterranean region east to mainland China. It is now common in North America as a weed[1]. Most of the species are herbaceous perennial plants, but some are annuals. They have sturdy stems with opposite heart-shaped, green to grayish-green leaves. The flowers are white, blue, pink, or lilac and occur in several clusters toward the tip of the stems. The flowers are tubular shaped and are spotted with tiny purple dots. The scent of the plant has a stimulating effect on cats. Also, it is claimed by some that the oil isolated from catnip by steam distillation is a repellant against insects. Research has shown this to be not the case with the yellow fever mosquito.[2]
Effects on cats
Catnip and catmints are mainly known for the narcotic and hallucinogenic effects they have on cats, particularly domestic cats. Both true catnip and Faassen's catnip have a sharp, biting taste, while the taste of giant catmint is bland. Approximately two thirds of cats are susceptible to the effects of catnip, as the phenomenon is hereditary. The fact that it only elicits such a response in a proportion of cats—and that it is such a dramatic response—suggests that a genetic element is involved that is enriched in domesticated breeds.
When cats sense the bruised leaves or stems of catnip, they will roll over it, paw at it, chew it, lick it, leap about and purr, often salivating copiously. Some cats will also growl and meow. This reaction only lasts for a few minutes before the cat loses interest. It takes up to two hours for the cat to "reset" and then it can come back to the catnip and have the same response as before. Young kittens and older cats are less likely to have a reaction to catnip. Lions and tigers are also sensitive to the effects of catnip.[3]
Catnip contains nepetalactone, a terpene. Nepetalactone can be extracted from catnip using steam distillation[4]. Cats detect it through their olfactory epithelium and not through their vomeronasal organ [5]. At the olfactory epithelium, the nepetalactone is hypothesized to bind to one or more G-protein coupled receptors on the surface of sensory neurons which are found in the sensory layer of the organ. Via a signal transduction pathway (probably involving a G-protein and a transient receptor potential channel) an influx of calcium ions that occurs creates an action potential along the axon of the neuron. The sensory neurons from the olfactory epithelium project to the olfactory bulb where multiple neurons (each expressing a single receptor type) synapse at special neuropil called glomeruli. Here the neurons synapse with mitral cells which, in turn, project to various brain loci, including the amygdala, where the signals are integrated into behavioural signals. There is some evidence of projections to the hypothalamus, which in turn regulates a neuroendocrine response via the pituitary gland. These hormones would mediate the "sexual response." The chemical probably hijacks the pathway normally influenced by a cat pheromone.
Other plants that also have this effect on cats include valerian (Valeriana officinalis) and plants that contain actinidine or dihydroactinidiolide (Smith, 2005).
Species
Nepeta cataria (Catnip, True Catnip, Catmint or Field Balm) is a 50–100 cm tall herb resembling mint in appearance, with greyish-green leaves; the flowers are white, finely spotted with purple. It has been introduced to many countries, and is now a widespread weed in some areas, including the United States. A lemon-scented cultivar, N. cataria 'Citriodora' looks exactly like true catnip, but has the scent of lemons, and can be used like Lemon balm.
Nepeta grandiflora (Giant Catmint or Caucasus Catmint) is lusher than true catnip, and has dark green leaves and dark blue, almost purple flowers.
Nepeta × faassenii (N. racemosa × N. nepetella; Faassen's Nepeta or Faassen's Catnip) is mostly grown as an ornamental plant. This hybrid is far smaller than either of above, and is almost a ground cover. It has greyish-green leaves and light purple flowers.
Some Dracocephalum, Glechoma and Calamintha species were formerly classified in Nepeta.
Nepeta species are used as food plants by the larvae of some Lepidoptera species including Coleophora albitarsella.
- Selected species
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Natural hybrids
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References
- ↑ Funk & Wagnalls New Encyclopedia, Vol. 5 (ISBN 0-8343-0051-6)
- ↑ Feeding deterrent effects of catnip oil components compared with two synthetic amides against Aedes aegypti. Chauhan, Kamlesh R.; Klun, Jerome A.; Debboun, Mustapha; Kramer, Matthew. BA, PSI, Chemicals Affecting Insect Behavior Laboratory, USDA-ARS, Beltsville, MD, USA. Journal of Medical Entomology (2005), 42(4), 643-646. Publisher: Entomological Society of America, CODEN: JMENA6 ISSN: 0022-2585. Journal written in English.
- ↑ [1]
- ↑ [2]
- ↑ [3]
- Jacobs, Betty E.M. Growing and Using Herbs Successfully. Garden Way Publishing. Pownal, Vermont, 1981.
External links
- Flora Europaea
- Flora of China
- Flora of Nepal
- Liber Herbarum II page on Nepeta cataria
- Catnip Repels Mosquitoes More Effectively Than DEET - reported at the 222nd national meeting of the American Chemical Society
- The Straight Dope: What is it with cats and catnip?
- What is in catnip anyway? Nepetalactone
- Catnip- Just for Cats?
- How does catnip work? HowStuffWorks, Inc. 1998-2005.
- Smith, L. Catnip. Penmarrie Cornish Rex. 1996-2005.
- Catnip Plants
