Catnip is a mint. That is the least interesting true thing about it, and also the most useful place to start, because almost everything people get wrong about the plant comes from treating it as a novelty rather than as a herb with a specific chemistry.
The plant is Nepeta cataria. The compound that matters to cats is nepetalactone, an essential oil stored in tiny glands on the leaves and flowering tops. Crush the plant, and those glands rupture. The cat smells it. For about two in three cats, that is enough.
What the plant actually looks like
Catnip is a perennial in the mint family, Lamiaceae, native to Europe, Asia, and parts of Africa, and now naturalised across much of North America. Heart-shaped, grey-green leaves with scalloped edges. Small white or pale lavender flowers in late summer. An upright, slightly weedy habit that can reach about a metre if you let it.
It is not the same plant as ornamental catmint, even though both sit in the Nepeta genus and garden centres mix the names constantly. Catnip is the one with the oil. Catmint is the one with the purple spikes.
The oil concentration is highest in the leaves and flowering tops, which is why those are the parts worth drying and the parts worth putting in a toy. Stems and powder made from the whole plant are weaker, and they fade faster.
How nepetalactone works
When a cat inhales the oil, the molecules bind to receptors in the nasal tissue. Signals travel to the olfactory bulb, then to the amygdala and the hypothalamus, the parts of the brain that handle emotion and behavioural response. The plant is, in effect, mimicking feline pheromones.
That is why the reaction looks social and physical rather than like a simple scent preference: rubbing, rolling, vocalising, grabbing, then a stretch of calm. Sniffing tends to excite. Eating a small amount tends to skip the excited phase and go closer to sleepy.
The whole sequence lasts about 10 to 15 minutes. After that the receptors stop responding for somewhere between 30 minutes and two hours, and no amount of fresh herb will produce a second round. That refractory period is normal, not a sign that the catnip has run out.
Who responds, and who does not
Sensitivity to nepetalactone is inherited. Around two in three cats have it. The remaining third do not, and nothing about freshness, quantity, or enthusiasm will change that. They are not being fussy. They are missing the receptor response.
Kittens usually do not react until they are between three and six months old, even if they will later. A young kitten ignoring catnip proves nothing.
For the third that never respond, the useful next plant is Silver Vine (Actinidia polygama). It works through a different set of compounds, mainly nepetalactol and actinidine, and it reaches about three quarters of the cats that ignore catnip completely.
What people actually use it for
The honest list is shorter than most articles make it.
Play. A pinch of dried herb, or a toy that holds enough of it, is a reliable way to start a hunt indoors. The cat still has to be able to grab and kick something. Smell gets them there; the object has to finish the job.
Scratching. Rubbing catnip into a new post, or spraying it, makes the post more interesting than the sofa for long enough that the habit can transfer.
Settling. After the 10-minute peak, most cats go quiet. That is useful before a car journey or in a new room, provided the cat is a responder and you time it so the excited phase is over before you need them calm.
People. Catnip tea has a long history as a mild evening drink. That is a different use of the same plant, and pet-aisle catnip is not food.
It is also a reasonably effective mosquito and fly repellent, which is probably why wild cats that roll in these plants pick up a useful coating. That is a side effect, not a reason to buy it.
Safety, in one paragraph
Catnip is not toxic, not addictive, and not a drug in any useful sense of the word. A cat that eats a large pile of dried leaf may vomit or have loose stools. That is fibre, not poisoning, and it passes. Offer it a few times a week rather than leaving it out, both to avoid habituation and to keep the oils from evaporating.
What to look for if you are buying it
Bright green, a sharp minty smell, and a named part of the plant. Brown, hay-like, or labelled only as "catnip" with no indication of leaf or flower is usually spent or padded.
In a toy, quantity is the thing most products hide. Under 5g of herb, bulked out with synthetic wadding, is common, and those toys are quiet within a fortnight. A fill of 30g or more, kept in a sealed jar between sessions, behaves completely differently.
That is why we put at least 30g of organic catnip buds, plus Silver Vine fruit, inside Le Croissant. The buds stay whole until the cat bites them, so the oils release during play rather than on the shop shelf. Reinforced OEKO-TEX cotton, hand-stitched in the South of France. The second herb is there for the cats that catnip cannot reach.