Barrel cactus are always cylindrical or barrel shaped and are usually among the largest cacti of the North American deserts. They have prominent ribs and are fiercely armed with heavy spines. Their flowers grow at the top of the plant. Fruits become fleshy and often juicy when mature, but are not usually considered edible. The Barrel Cactus Postcard includes a seed packet, detailed planting instructions, and an information packet.