Maca is the only known cruciferous crop from the Americas. Maca is traditionally cultivated at the upper altitude limits for agriculture only in the Central Peruvian Andes. No other crop plant, except bitter potatoes, gives reliable yields at 4400 meters. It is believed to possess fertility-enhancing properties. Interest in maca has been reactivated recently, as local people believe it improves physical and mental capacities, strengthens sexual stamina, and enhances the immune system. Capsules of dehydrated maca roots are available in drugstores in Lima, Peru.