Catmint, better known as catnip (Nepeta cataria), is a hardy grey-green mint whose softly downy, heart-shaped leaves give off a musky, camphor-and-mint aroma when bruised. Long grown in kitchen and physic gardens, its leaves and flowering tops were used fresh or dried as a homely minty tea and pot-herb — and as a stand-in for garden mint — while the same volatile oil that flavours it famously sends many cats into a rolling, euphoric frenzy.