Catnip (Nepeta cataria L.) is a perennial herb that is found in Europe, Central Asia, and North America. Catnip is not native to North America, but it is well acclimatized in many areas of the United States. Catnip is used as a cat toy filler and medicinal tea. We determined the effects of three irrigation regimes on the physiological, anatomical and growth traits of catnip. In one experiment, plants were irrigated every two days, five days, and 10 days for 12 weeks. Irrigation regime did not affect leaf dry weight, the ratio of root to shoot dry weight, and specific leaf weight. Root and shoot dry weights were lowest in plants irrigated every ten days and averaged 142 and 19 grams per plant, respectively. Average total leaf area of plants irrigated every ten days was the lowest and averaged 934 cm2. Leaves from plants irrigated every five days had the thickest palisade layers. In another experiment, plants were irrigated every other day, five days, and ten days for six weeks. Irrigation treatment affected leaf maximal fluorescence. Plants irrigated every 10 days had stomatal conductance rates that were reduced to as little as 82% of plants watered every other day. We conclude that plants watered every ten days accumulated the least dry mass. Irrigation regime affects both physiological and anatomical traits of catnip. Effects of those three irrigation levels on the accumulation of essential oils in catnip are being investigated.

Key words: Catmint, Chlorophyll Fluorescence, Drought, Labiatae, Nepeta cataria