The most commonly used species of catnip is Nepeta cataria. This species is used most prevalently for medicinal purposes and it has the most effect on cats compared to other species in the genus. The dried herb can often be found in pet or grocery stores being sold as a recreational substance for cats.
Dried herb meant for cat consumption tends to have a weak potency and many people attempting to use this form of catnip report that it has little to no medicinal or recreational value. Dried herb sold specifically for medicinal purposes tends to be more potent and effective, but the potency will vary with the age of the material, storage method, and the location from where it was harvested due to genetic variations and environmental factors.
The highest quality of catnip is obtained by collecting wild plants, properly drying, and properly storing them in an air-tight container. This ensures that the least amount of volatile active compounds will be lost.
Other species of catnip are used for medicinal and recreational purposes. Some of these species are also reported to have stronger medicinal properties, particularly the hybrid Nepeta x faassenii.