 Lettuce production methods , including all of the processes from growing to sales , have become much larger in scale during the 20th century . The majority of agricultural production is done with the application of large amounts of chemicals , including fertilizers and pesticides , but organic production makes up a growing percentage of the market – a trend that began with small growers but moved to a more industrial scale . More non @-@ heading types , mostly leaf and romaine lettuces , are also being grown . In the first years of the 21st century , bagged salad products began to hold a growing portion of the lettuce market , especially in the US . Processed from what was previously waste lettuce not considered acceptable for the fresh market , these products are packaged in a manner that makes them last longer than standard head lettuce after harvest . As of 2007 , 70 percent of the lettuce production in the US came from California ; in that country it ranks third in produce consumption behind tomatoes and oranges . 
