As its name suggests, Green Oak Leaf lettuce has the appearance of Oak leaves – linear, lobed and loosely serrated. The leaves form a semi-tight rosette at the base, growing upward and outward. Red Oak Leaf lettuce has a buttery texture and an incredibly mellow, nutty and sweet flavor, which rarely becomes bitter, even in hotter climates.. Mature Size: 10″ x 10″. Full Sun (6+ Hours).