This morning, I half-expected to see watermelons and peaches at the Greenmarket. Instead, in the blazing sun, hot mulled cider was standing by while shoppers peeled off a few layers. The sweet potatoes and turnips looked all wrong. The brussels sprouts seemed like a joke. But, even those of us plagued by seasonal affective disorder can get excited about crisp, juicy Asian pears, esoteric turnip strains, like the one called “MOO” at Yuno’s Farm, and on-the-cob popping corn.