(Lactuca sativa) We acquired this dark green classic Pennsylvania Dutch winter lettuce in 1994 from the well-known lettuce collector Mary Schultz of Monroe, Washington. A Pennsylvania Dutch selection of the now-extinct late 1700s variety known as White Tennisball, this is one of the hardiest, most frost-resistant lettuces we have ever grown. It even survived the Polar Vortex during the severe winter of 2013-2014. Each head reaches 11 to 12 inches in diameter with a loose butterhead appearance. Plant 14 inches apart in early September for salad greens through December and January.