Salad greens are usually picked at an immature size and coaxed into regrowing several times. They are a perfect choice for container gardening, as long as a good soil mixture is in place.
Season & Zone
Season: Cool season
Exposure: Full sun to partial shade
Seed every three weeks from March to September for a continuous harvest. Provide frost protection with a cloche or heavy row cover starting in late October, and many mesclun types and mixes will continue to grow all winter.
Plant in a block or in a wide row. Sprinkle the seeds evenly over prepared, moist soil. Try to space seeds about 1cm (½") apart. Cover lightly with soil, and firm them in. Four grams of seed will plant a 12m (40') row that is 7cm (3") wide, so don't plant the whole packet at once. For container growing, choose containers that are at least 10cm (4") deep. Wider is better. The most common mistake is over-planting.
Moderately fertile soil - particularly if you're planning mutliple harvests. Dig in 1 cup of complete organic fertilizer for every 3m (10') of row. For containers, use peat or coir based mix with compost added. Water regularly. If growth slows after harvest, use a bit of kelp or fish based fertilizer to provide a boost of nutrition for the next growth spurt.
There are two methods of gathering salad greens. You can use scissors to cut everything about 2-5cm (1-2") from the ground, when the plants are about 10-15cm (3-4") tall. Or, you can pick individual leaves as they're needed. The first cutting may contain more brassicas than lettuces (arugula, mizuna) but if you cut the mix back when the leaves are still small, the lettuce will catch up. The salad greens will regrow for a second harvest in another 2 or 3 weeks.
Diseases & Pests
Slugs love baby greens and flea beetles love brassica leaves.