Growing lettuce-Lettuce grows best in cool weather. Plant as early as possible and successively every 2 weeks in spring and again in late summer for a fall crop. Head lettuce may be started indoors for earlier harvest. Iceberg or head lettuce are the types most commonly purchased in the grocery store. They tend to be more heat sensitive than other types. Our Calmar variety is widely adapted and well suited for growing in home gardens. A packet contains about 1000 seeds except where noted and will sow 50 feet. An ounce = 300 feet of row. There are approximately 20,000-25,000 seeds per ounce. Plant more than one variety for a longer harvest season.