The main difference between a turnip and a rutabaga is that the turnip dates back to Paleolithic times. The rutabaga is an 18th-century invention, a cross between a turnip and a cabbage.
Rutabagas are larger than turnips. Their flesh is yellow and features a purple top; the yellow becomes brighter after cooking. Their texture is rough, and they contain more starch than turnips. They also have a sweeter flavor than turnips. Rutabaga season is generally September to June, though they are available year-round.
Turnips are smaller than rutabagas. Their flesh is white and features a purple top. The flesh stays white during cooking. Turnips have a smoother texture than rutabagas. Their flavor is more bitter. Turnip greens, or the tops of the turnip, are more commonly used than rutabaga greens. Turnip greens can be cooked or served in salads. Turnip season is generally October to March, though they are available year-round.
Nutritionally, turnips and rutabagas are similar. A 100-gram serving of turnip has 28 calories, while 100 grams of rutabaga contains 38 calories. They are both good sources of vitamin C, with a serving of turnip fulfilling 35 percent of the daily value. A serving of rutabaga fulfills 41 percent of the daily value. Rutabagas do have more potassium, sugar and dietary fiber than turnips.