|'Philadelphia Oak Leaf' is an heirloom variety which is very hardy and will overwinter in cold frames in the North, and outdoors in the South. The plants are green in color, and grow into 24 inch rosettes. The leaves are heavily lobed, and have a lobe resembling a finger at the tip of each leaf. The seed is white. Start from seed 4 to 6 weeks before average last frost date. Sow seeds 1/4 inch deep in wide rows and thin to 8 to 12 inches apart. Thinned seedlings can be replanted. Keep soil moist but not soggy. Protect from rabbits and slugs. Extend the harvest season by planting successive crops. Summer heat causes lettuce to bolt. Pick outer leaves as they grow or harvest all at once. Harvesting when weather or day temperature is cooler will result in crisper leaves. Do not harvest lettuces until you are ready to use it.