554 VEGETABLE GARDENING 



Eclipse or Express, Dwarf White Heart and Paris 

 White are excellent varieties of the cos type (also known 

 as the Romaine). Hanson, Iceberg,* and Brittle Ice are 

 well-known varieties of the solid, "crisp-head" lettuces. 

 The butter varieties are best represented by Dutch But- 

 ter, All Seasons, California Cream Butter, and Deacon. 

 Big Boston is grown most largely as a head lettuce in the 

 open ground. Other varieties valued for field planting 

 are May King, All Heart and Sensation. Grand Rapids 

 is the most popular loose-leaved bunching variety grown 

 in the western greenhouses. The various strains of 

 Tennis Ball meet with the greatest favor among eastern 

 greenhouse growers. 



There are over loo distinct varieties of lettuce, which 

 show the widest variation in size, color, solidity, texture, 

 leaf-formation, flower, quality, disease resistance, tender- 

 ness to heat or cold and time required to attain maturity. 

 The three best-known and most largely grown varieties 

 in America are Big Boston, Black-Seeded Tennis Ball 

 and Grand Rapids. . 



490. Climatic requirements. — Lettuce is a cool weather 

 plant. It stands cold much better than heat. The 

 tendency of many varieties is to produce seed shoots 

 prematurely when an attempt is made to grow them in 

 midsummer. The large markets are supplied by various 

 regions which furnish the best conditions as the season 

 advances and by the use of glass and artificial heat dur- 

 ing the winter. When properly hardened the young 

 plants will stand even lower temperatures than cabbage 

 plants. A drop of 20 degrees below freezing will cause 

 no injury if the plants have been fully hardened. The 

 matured crop is more easily damaged by severe freezing. 

 Notwithstanding the fact that lettuce is a cool weather 

 plant, it is grown all summer in most parts of the North, 

 due largely to the adaptation of varieties to various 

 climatic conditions. The young plants are wintered 



