Sweet Violet and Ionone

The sweet violet has a peculiarity worth knowing. It contains a compound called ionone, which briefly disables the olfactory nerves on contact. You smell it, then it disappears, then it returns a few moments later as though nothing happened.

This is not your imagination. The violet keeps vanishing and reappearing, which accounts for centuries of people pressing their faces into the same patch of flowers wondering what happened to the scent.

Ionone — specifically beta-ionone — binds to the scent receptors and temporarily saturates them. The receptors shut down, the smell disappears. A few moments later, as the receptors recover, the scent returns. The cycle can repeat indefinitely. The violet has not changed. Your nose has.

The phenomenon was noticed long before the chemistry was understood. Culpeper noted the fleeting quality of the violet's scent. Perfumers have worked with ionone since the nineteenth century, prizing it precisely because of its vanishing quality — a perfume that fades and returns is more interesting than one that simply persists.

Sweet violets — Viola odorata — are at their best in March and April, low to the ground, preferring the base of a wall or a shaded bank. They are easy to miss entirely, which is part of the point. The scent is what finds you, not the other way around.

Herbalists used the flowers and leaves for coughs and sore throats throughout the medieval and early modern period, made into syrups for winter chests — a cold-weather remedy gathered and bottled in early spring, before the flowers closed. The syrup, when it comes, is a deep and rather improbable blue-purple. Add a few drops of lemon juice and it shifts to pink in seconds. The anthocyanins in the petals work as a natural indicator of acidity.

The Cottage Almanac covers seasonal plants, still-room recipes, and the natural history of the British countryside every Thursday. Subscribe free to get the Thursday letter.