The Chile de árbol (Spanish for tree chilli) is a small and potent Mexican chilli pepper also known as bird’s beak chilli and rat’s tail chilli. These chillies are about 5 to 7.6 cm long, and 0.65 to 0.95 cm in diameter. Their heat index is between 15,000 and 30,000 Scoville units. The peppers start out green and turn a bright red colour as they mature. Chile de árbol peppers can be found fresh, dried, or powdered. As dried chillies, they are often used to decorate wreaths because they do not lose their red colour after dehydration.
In cooking substitutions, the Chile de árbol pepper can be traded with Cayenne pepper (30,000–50,000 Scoville units) or Pequin pepper (100,000–140,000 Scoville units). The seeds and white arches can be removed from the pepper to tone down its hotness.