The salad garden can include many varieties of leafy plants, lettuce, spinach, kale, Swiss chard and many others, including many varieties of each of those plants.
Lettuce;
Crisp heads, 90 days to mature (best for fall crops)
Butter heads, 60-95 days to mature
Romaine’s (cos lettuce), 75 days to mature (good all season long)
Loose-leaf, 40-60 days to mature. (Can be continuously harvested)
Lettuce can be sown indoors about 4 weeks before last frost, and tolerate light frost. You can also plant seeds directly in the garden around mid-May. Lettuce does best with rich soil. Try to space seeds about every 3-4 inches apart for loose leaf varieties, 6-8 inches for romaine and butter heads and 12-16 inches for crisp heads. To get the most out of your lettuce, try planting seeds every few weeks, otherwise you'll harvest it all at once. You can start sowing seeds in mid-may up until mid-august. Remember once your lettuce starts to bolt (grow upwards into a stall plant) it’s going to seed. Lettuce that goes to seed become very bitter tasting and not something anyone enjoys eating. Roots are shallow so keep free of weeds and water lots! Leaf lettuce can be harvested by picking off some of the outer leaves as needed or by cutting the entire head about 1 inches from the soil. Heading lettuce is best when still soft. The firmer the head the more bitter it will taste. So harvest when still young. Lettuce will keep well for about a week in the fridge.
Kale
Kale is a biennial and won't bolt the same year like spinach and lettuce do. Grow kale the same as you would lettuce, but don't worry about bolting. You can harvest kale throughout the year as a cut-and-come again green, or purple or whatever colour or variety of kale you happen to be growing!
Spinach
Grow spinach just like lettuce or kale. It does bolt fairly early though. You can also cut spinach as needed by cutting outer leaves when young. You can also harvest the entire plant, leaves are tastiest when small.
Exotic greens;
Arugula
Arugula grows well in almost any soil type. They grow best in spring and fall or in a shady spot during summer. If you keep your seeds spread out arugula spreads over the ground, but sown thickly it tends to grow upward. Leaves are tastiest when 2-6 inches tall. Stores like lettuce.
Corn salad
Very sweet tasting lettuce, and can be grown even in October. Light frost can actual help intensify the sweet flavor! Corn salad can be sown outdoors as soon as the soil is workable, and it loves a well-watered bed. Plant about 4 inches apart and harvest the leaves in about 45-60 days. Even when corn salad bolts it doesn't become bitter. You can plant corn salad in late July and still receive a nice fall crop.
Purslane
Spreads quickly and can over take a garden best grown alone or separated. Purslane has a mild citrus flavor. It loves heat and is drought resistant, Can be sown in late May, and harvested as a cut-and-come again vegetable. Around mid-August you may notice the leaves get tough, they often lose their flavor when this happens. They are a good self-seeder so if you don't want more next year, Dig 'em up!