The main leaf crops are arugula, lettuce, dandelion, endive, spinach, kale, mustard leaves, and radicchio, and each has a specific taste from bland, to bitter, from delicate to peppery. Even among the lettuces there is a wide variety of types: head forming like iceburg, butterhead, and romaine, and loose-leaf varieties. This link will take you to a taste description of each type of green. http://www.foodsubs.com/Greensld.html Greens like arugula and dandelion, which have strong tastes, are usually picked when the leaves are very young to help tame the taste.
Seed companies have become very smart in marketing leaf crops. Rather than buy one packet of one variety of leaf crop, you can now buy packets that mix them so you can grow them all together in one patch. However, even the selection of salad mixes has become an ever expanding group of seductive names like All-Star Gourmet, Encore, Mild Musclun Mix, and Wildfire, allowing you to truly enjoy a mixed to your taste salad bowl. When you pour some of the seed out into your hand, you will see the mix is usually very pretty, too, with black, white, red, and brown seeds in round, oval and thistle shapes.
Even the greenest gardener can grow lettuce. If you don't want a vegetable garden, then grow these tender leaves in large outdoor pots filled with potting soil. The plants are very decorative until you harvest a meal's worth of leaves, but even the de-leafed plants quickly come back. Two or three 14" containers would supply your family with plenty of dinner salads. Wash the greens, roll them in a dish towel and refrigerate them so they will become crisp. Enjoy your salad days!