Lettuce Farming Locations
Lettuce is used in the Chef profession and, much like a lot of the other more rare gathering materials can only be found in patches across the world. However Lettuce seems to have many more gathering locations than other rare cooking materials such as Grapes or Cauliflower. Most of the time I actually recommend you buy it from the Trading Post as Lettuce commonly goes for 4 - 8c each. Allowing you to buy a ton of it for dirt cheap prices.
Northern Caledon Forest Lettuce Location
This location for gathering Lettuce is in Northern Caledon Forest just north of Kraitbane Haven Waypoint.
Lettuce Gathering at Beetletun Farm
Located in Northeastern Queensdale just south of Cadeus' Manor Instance.