Iceburg Lettuce Seeds (Crisphead Type) 1775 Heirloom Vegetable. The classic heading lettuce was first introduced in 1894! A compact, medium headed lettuce with very few outer leaves and a large ice-white heart. Exceedingly crisp, succulent and tender leaves. An all-time winner! An even supply of soil moisture is essential for best head development. How to Grow 880 seed/gram. Lettuce is a sun-loving cool weather crop that grows best in organic, well drained soil. Sow as soon as the soil can be worked in the spring, then every two weeks thereafter to ensure a continuous supply. Sow about 3 mm (1/8″) deep in rows 45 cm (18″) apart. Gradually thin seedlings to 30 cm (12″) apart. An even supply of moisture during the entire growth period is imperative for success. Harvest head lettuce by cutting the head off the base just below the lower leaves. Once lettuce bolts (starts to produce a rapidly growing flower stem) leaves become bitter.
