By Kim Snowdon, Colorado Master Gardener “Lettuce celebrate the goodness of greens!” — author unknown Cool-season salad greens are an easy garden crop for your raised bed or a container on your patio. A vegetable is considered a cool-season crop if it thrives in temperatures between 50 degrees and 70 degrees. And there’s nothing more satisfying than harvesting a few tender leaves as the basis for a fresh and creative meal. Lettuce, arugula, mizuna (similar to arugula but with a milder peppery taste), chervil, escarole, cress, kale and Swiss chard are some of the varieties of greens that can be sown for salads. Dark and colorful leaves are usually more nutritious, and you can grow more unusual varieties than are available at the grocery store. Sow in good quality potting soil as soon as the soil can be worked in the spring, about 3 to 4 weeks before the last frost (usually mid-May).…