Irrigation Amounts

• Lettuce should receive about 1 inch of water per week during warm summer weather, as National Gardening Association experts suggest. If it rains less than 1 inch during a week, provide supplemental irrigation for lettuce plants. In the spring and fall, some geographic areas will get enough rainfall that lettuce will not need extra irrigation. Since lettuce grows best in temperatures below 70 degrees Fahrenheit, plant lettuce in somewhat shady areas to keep them cool and prevent irrigation from evaporating quickly during hot weather.
  
  

Irrigating Lettuce Seeds

• After planting lettuce seeds, mist them regularly to keep them moist while the germinate. Do not mist them so much that the seeds sit in saturated soil, but keep them evenly moist. Once the seeds sprout into small seedling plants, start watering them instead of misting them.
  
  

Irrigation Technique

• Lettuce plants have shallow roots, so they do not tolerate droughts well. Stay on top of waterings to keep lettuce from drying out when the top layer of soil dries out. Water lettuce plants frequently and shallowly to help them grow quickly. Do not overwater or soak the soil, because lettuce plants do not grow well when their roots sit in water. To check whether lettuce plants need more water, stick a finger in the soil to see if it feels dry to the touch beneath the surface.
  
  

Considerations

• Water lettuce in the morning, as a University of Maryland plant expert recommends. Morning waterings give the plants time to dry off during the day. If lettuce plants stay wet overnight, they are likely to develop fungal or other disease problems. Also water lettuce more during warm weather than cool weather, and water it more in sandy soils with rapid drainage than in heavy clay soils with slow drainage.