Radishes!
Radishes aren't capsaicin spicy, but they are a member of the mustard family and can have a strong, peppery flavour.
Radishes contain natural chemical compounds called glucosinolates, which aren't firey by themselves. When a radish is bitten into, an enzyme called myrosinase is triggered, to break down the glucosinolates into various metabolites. This includes pungent compounds known as isothiocyanates, which produce the flavour.
In Oaxaca they hold a festival called Night of the Radishes, where large radishes are carved into various scenes.
I created this page because I had a craving for radishes, and I have fond memories of eating them from the garden when I was a child. Unfortunately, I cannot find any in the supermarket near me. If you can find radishes, you can eat them raw, in a salad, or with butter and salt (as I've heard the French do).
They may be spicy or mild, because it depends on the growing conditions; with warmer weather and stressful conditions producing more pungent radishes. Happy eating!