Romaine or cos lettuce (Lactuca sativa L. var. longifolia) is a variety of lettuce that grows in a tall head of sturdy dark green leaves with firm ribs down their centers. Unlike most lettuces, it is tolerant of heat. In North America, romaine is sold as whole heads or as âheartsâ that have had the outer leaves removed and are often packaged together. Commercially sold romaine lettuce has occasionally been the subject of product warnings by both U.S. and Canadian health authorities warning that consumer supplies can become contaminated with or host pathogenic E. coli bacteria.
Iceberg lettuce doesn't set deep roots, so it requires proper irrigation to keep the root zone moist. Watering the bed when the top inch of soil feels dry is usually sufficient. Depending on how cool and moist the weather is, the lettuce may require watering every five to 10 days.
Feed lettuce plants every two weeks with a balanced water soluble or granular fertilizer, such as a 10-10-10 or a 5-5-5, diluted to half strength.
Check the seed tray every day, and water the seeds whenever the soil feels dry. You want the soil to be moist but not soaked. If there's standing water on top of the soil, the seeds could rot. In five to ten days you should see the lettuce beginning to sprout.
Site Needs. Lettuce thrives in the cool spring season so it requires planting in early spring once soil temperatures are above 60 degrees Fahrenheit. Iceberg lettuce also makes a suitable fall crop when planted in early fall after temperatures begin to cool.
Because they have shallow roots, most lettuce varieties will grow well in long and shallow containers.
