Long pepper is a spice from the plant of the genus and species Piper longum, which has been used for centuries in the Mediterranean, and in Indian, African, and Indonesian cooking. This unusual plant has a peppery taste similar to black pepper, though most consider it hotter, and in fact P. longum is a relative of the black pepper plant, P. nigrum. Today long pepper is mostly used in the countries mentioned above. Popularity of new world peppers largely replaced the use of long pepper in European cooking.
The plants on which long pepper fruits grow are quite unusual. They are flowering vines with large catkin flowers. Within each flower lie tiny black spikes, each comparable in size to a poppy seed. These spikes make up the spice long pepper, and the catkin is usually harvested whole, then dried for use in cooking. Significant use of this type of pepper extended from India, where it was likely first cultivated, to parts of Asia and most of the Middle East. Greek references to long pepper date back to the 4th century BCE. Medieval Europe certainly made use of the spice, both as food flavoring and for its supposed medicinal properties.
As with many ancient herbs and spices, long pepper had a dual role as a medicinal and as a cooking ingredient. In Aryuvedic medicine, long and black pepper and ginger are used together to created trikatu, a base ingredient for thousands of medical remedies. Alone, P. longum might be used to help with coughs, colds, fevers, and a variety of stomach conditions.
It was also believed that spices had a role in masking the flavor of spoiled or spoiling meats. In the past, refrigeration was either not available, very expensive, or not very effective. This meant that keeping food fresh was difficult. While it was once thought that spices were used to cover up the taste of bad meat, this theory has been disproved.
Both Attila the Hun and Alaric the Visigoth demanded ransoms of long and black pepper when they besieged Rome in the 400s CE. These spices were currency, in addition to providing food with flavor. Given the importance of long pepper, you would expect it to be in continual use in the present day. In fact it isn’t, even in Indian cooking. A few recipes in traditional Indian dishes, like pickles, call for the pepper, but it is now used less frequently.
It’s therefore difficult to find, though you may have some luck purchasing it at Indian run grocery stores. It’s also available on sites like Amazon — expect to pay a lot for it. A few ounces can cost over $10 US Dollars (USD). Of course, you should plan to use the spice more sparingly than black pepper since it imparts much greater heat.