Farmers’ markets are open and fresh greens are center stage. And don’t we love ‘em? They’re one of the easiest ways to boost your immune system! There are seven green powerhouses that are especially efficient at this boosting job. For instance, seriously consider these seven greens and tips from the pros on how to prep them:

KALE: Noted as the darling of the greens world, and for so many good reasons. Curly kale is deep green with ruffled edges. Tuscan kale, aka dinosaur or black kale, has bumpy blue-green leaves. It is sweeter in winter, but it's packed with nutrients year-round. Just one cup of raw kale supplies a day's worth of vitamins A and C and six times the daily requirement of bone-boosting vitamin K.

Kale makes delicious snacking chips: Strip the leaves from the tough stems and tear them into 2-inch pieces. Toss with olive oil and salt and bake at 350°F for 10 to 15 minutes, or until crispy. Or, for a simple no-cook side dish, slice kale into one-inch ribbons, add a tablespoon each of olive oil and lemon juice and a dash of salt; then gently massage with your fingertips until the leaves are wilted. Top with freshly ground black pepper, nuts or seeds for crunch, and either avocado slices or a sprinkle of pecorino.

SWISS CHARD: Eye-popping red, yellow, orange, or white stalks signal freshness. This somewhat salty relative of the beet is a top source of vitamins A and C. And one cup of cooked Swiss chard delivers more than 20% of your daily quota for iron.

Both the stalks and the leaves are edible. To soften the leaves, blanch them for a few minutes; then sauté with olive oil and garlic and toss with golden raisins. Or wrap seasoned fish fillets in the blanched leaves and bake. For a side dish, cook the stalks, then chop each into three or four pieces and boil in water with a squeeze of lemon juice for five minutes. Toss with olive oil and Parmesan; then broil for 10 minutes.

COLLARDS: They resemble wide, flat cabbage leaves. Look for a deep green hue. Research shows that this mild green is better at lowering artery-clogging cholesterol than broccoli or spinach. Remove the stems and slice the leaves into two-inch pieces; meanwhile, fry turkey bacon in olive oil. Crumble bacon and sauté it with the collards and garlic. Add enough chicken stock to just cover the greens, reduce the heat to low, and simmer for an hour, or until tender. Finish the dish with a splash of apple cider vinegar and red pepper flakes.

BOK CHOY: Also known as Chinese cabbage, you want thick, firm stalks with bright leaves. This mild, slightly sweet cousin of cabbage is a super source of calcium because it's low in oxalate, a compound in many greens that blocks absorption of the mineral. It also has 25 kinds of cancer-fighting antioxidants called polyphenols.

Small, tender baby bok choy is great in stir-fries or tossed with oil, salt, and black pepper and roasted at 400°F for five minutes. You can make a delicious side dish with the stalks by chopping and sautéing them in oil with garlic, ginger, and reduced-sodium soy sauce for three to four minutes. Then add the leaves a few minutes before serving, so that the stalks are tender and the leaves are just wilted.

TURNIP GREENS: They’re on the delicate side. Avoid wilted or yellow leaves, or any that have slick dark green patches. They have a strong flavor and cabbage-like texture. Loaded with fiber and vitamin K, one cup of cooked greens fulfills 20% of the daily requirement for vitamin B6. Blanching them will soften their “bite."

Sauté them in olive oil with garlic and finish with a little lemon juice or apple cider vinegar. Or sauté garlic, onion, and lemon zest in olive oil; add the greens and white wine and simmer until soft. Then puree in a blender and serve as a dip with crusty bread.

WATERCRESS: The small, oval-shaped leaves should smell peppery. Watercress is loaded with vision-protecting carotenoids and compounds that inhibit the growth of breast cancer tumors.

To serve, trim stems, then add the leaves to sandwiches, frittatas, and salads. They’re wonderful paired with a sweet balsamic vinaigrette. Cress makes a lovely garnishing bed for roast chicken or beef.

And combined with a sauteed cubed potato and a diced onion, it makes a scrumptious soup. Just simmer the sauteed spud and onion in two cups each of low-fat milk and chicken stock for 10 minutes, or until tender. Then add two cups of watercress (leaves and stems), cook five minutes more, and puree until smooth. Garnish with fresh watercress leaves and low-fat sour cream.

ESCAROLE: You want tightly packed unblemished leaves. It looks like romaine, but unlike romaine, it has a firm texture, paler color, and slightly bittersweet taste. At just eight calories per uncooked cup, this nutrition superstar supplies fiber and heart-healthy folate, along with vitamins A, C, and K.

The inner leaves are sweet and mild, so they work well in salads. To prep, use a paring knife to cut off a thin slice on the stem end, then remove the core. Toss with olive oil, lemon juice, salt, and pepper and top with shaved Parmesan. The outer leaves provide nice texture and flavor when added to minestrone and turkey chili.