Proboscidea louisianica aka Ram's Horn

Proboscidea louisianica is an annual native from the United States to Mexico. Kew places it in the family Martyniaceae. Its common names include devil's claw and common unicorn plant. These names draw attention to its horned seed capsules. Its native range includes the central and southwestern United States. It also extends across much of Mexico. The plant grows in subtropical regions, along riverbanks and on disturbed ground.

Plants reach about 3.3 feet [1 metre] in height. Each plant completes its life cycle in one growing season. Flowers appear from July to September. Each flower has both male and female organs. The seed capsules bear long, pointed horns. These horns provide material for dark patterns in coiled baskets. The pods also yield a black dye. This gives the plant a craft use beyond the garden.

Grow this species in a warm, sheltered spot with full sun. It needs moist soil that lets excess water drain away. Sandy, loamy and clay soils can all suit it. It accepts mildly acid, neutral and mildly alkaline soil. Good drainage matters more than any one soil texture. PFAF lists USDA zones 9–11, but the plant cannot withstand frost. In Britain, gardeners can grow it as a half-hardy annual. Sow seeds under glass in spring, with warmth. Move seedlings into separate pots once large enough to handle. Plant them outside after the risk of frost has passed.

The species has sometimes served as a food crop. Pick young fruits while a fork can still pierce them. Sliced fruits can help thicken soups. They can also be briefly boiled and served as vegetables. Another use is to pickle the young fruits in vinegar. The seeds can be eaten raw or cooked. They contain protein and oil, and yield an edible oil. PFAF also lists the root as edible, without preparation details.

The plant suits cultivated beds where warmth and drainage meet its needs. Its unusual capsules also supply useful craft materials. It has escaped cultivation and become a weed in Portugal and southeastern Russia. That history warrants care where it might spread beyond garden beds. PFAF reports no known hazards, but this does not establish safety for pets. It lists no known medicinal uses. The supplied sources give no specific pest or disease problems.