Heat tolerant variety for hearts. The most tipburn resistant, Helvius Romaine makes heavy, dense hearts. Ideal for midseason harvest. Packet: 30 seeds. Days to Maturity or Bloom: 44-58 CULTURE: Lettuce is hardy and can be planted as early as the soil can be worked. It is a cool weather crop and makes its best growth at temperatures of 60-65°F (16-18°C). Careful variety selection is important for hot weather crops. Sow every 3 weeks for a continuous supply of fresh lettuce.