Next week we turn to specialty and gourmet markets in search of seasonal produce and other ingredients. We'll return to Union Square with springtime's ramps and fiddleheads; in the interim, stalwart Greenmarketers can look forward to a winter's worth of greens, onions, garlic, potatoes, and apples — not to mention fragrant rosemary garlands, cranberry-pecan sourdough, guinea hens, Christmas trees, and jars of golden pear chutney.