One of the easiest salad greens you can grow is arugula. Even if all you have is an 8" pot on your back porch, you can grow it. All you need is an area that gets at least 6 hours of sun. It will grow in less, but the leaves aren't quite as flavorful. And what a wonderful flavor! Arugula adds a nice peppery bite to salads, sandwiches and pasta.
Arugula seeds should be sown directly in the ground when temperatures are cool. In my zone 7 garden I grow arugula in the spring and fall. If you live in an area where summers are mild you can grow arugula continuously over the season by sowing seeds every week or two.
Sprinkle the seeds in narrow furrows that are 5 inches apart and cover with 1/4 to 1/2 inch of soil. Keep the soil evenly moist and the seeds will germinate in about 10 days. The plants are ready to harvest in 5 weeks when the leaves are about 4 to 6 inches tall and just beginning to form lobes. If the leaves become too mature they can taste bitter.