Some people comb through neighborhood yard sales and secondhand stores to find that one-of-a-kind treasure. Agricultural Research Service plant geneticists used similar tactics — but on a much larger scale — in his search for distinctive varieties of Carolina collards. Collard, a cole crop related to broccoli, cabbage and cauliflower, has always been a local staple in the South. But its commercial cultivation expanded dramatically in the 20th century, and is now dominated by a few hybrid varieties.