Arugula is a peppery flavored salad green. In Roman times Arugula was grown for both it’s leaves and the seed. The seed was used for flavoring oils. On another interesting note, Rocket or Arugula seed has been used as an ingredient in aphrodisiac concoctions dating back to the first century, AD. (Cambridge World History of Food).
It can be directly sown into the garden though early August in successive plantings at about 5 inches apart. Hot weather causes it to go to seed, which is why successive plantings are a good idea. It is usually used sparingly in salads to add a sharp, nutty flavor. It can also be cooked or tossed into pasta.