Answer: One other cause of bitterness in lettuce is slow growth--often caused by a lack of water. So be sure to keep plants well watered throughout their growing season. You could experiment with your soil theory by creating a raised bed, bringing in a load of topsoil from another source. Or try raising a crop to maturity in a container. You also might try planting a mix of lettuce, such as Burpee's Gourmet Blend, and taste-testing the different varieties..
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