You waited until the last spring frost and quickly sowed the seeds for your lettuce bed. Within weeks, the head lettuce was ready to be thinned and the loose leaf varieties were ready for their first gentle harvesting. Nothing tastes better than crisp lettuce straight from the garden. Soon, spring passed, summer heat arrived, and gardening websites like this one are inundated with questions: Why is my lettuce bitter? Why does lettuce turn bitter? What makes lettuce turn bitter? Is there any help for bitter tasting lettuce?
Common Causes of Bitter Lettuce
Most gardeners will tell you that bitter lettuce is the result of summer heat; lettuce is known as a cool season vegetable. When temperatures rise, the plant snaps into maturation mode and bolts — sends out a stalk and flowers. It’s during this process that bitter lettuce is produced. This is a natural process that can’t be stopped, but it isn’t the only answer to what makes lettuce bitter.
Too little water can also cause bitter lettuce. Those large, flat leaves need a large amount of water to remain full and sweet. Brown leaf edges are a sure sign that you lettuce is thirsty either from lack of water or root damage from close cultivation. Water regularly and well. Don’t let the bed become bone dry.
Another answer to why does lettuce turn bitter is nutrition. Lettuce needs to grow fast. Without proper nutrients, growth becomes stunted and bitter tasting lettuce is the result. Fertilize regularly, but don’t get carried away. Some studies suggest that bitter lettuce can also be the result of too much nitrogen.
Lastly, aster yellows phytoplasma, commonly called aster yellows, is a disease that can cause bitter lettuce. With this infection, the interior leaves lose color and the outer leaves become stunted. The whole plant can become deformed.
Why is My Lettuce Bitter and What Can I Do About It?
Most likely, your bitter lettuce is the result of the maturation process. There’s no way you can completely stop Mother Nature, but there are ways you can delay the result.
Mulch your lettuce to keep the roots cool and fool the plant into thinking its still spring. Interplant your lettuce with taller crops to provide shade as the weather warms. Succession planting will also help extend the season.
If you think nitrogen might be the cause of your bitter tasting lettuce, add a small amount of wood ash to your soil.
Some people have found it helpful to soak their bitter lettuce prior to using. If you would like to give this a try, separate the lettuce leaves, put them in a bowl of cold water and add a small amount of baking soda. Let the leaves soak about five to 10 minutes, rinse thoroughly in cold water and then soak them again for a few more minutes. Drain and use.
You can also try refrigerating the bitter lettuce for 24-48 hours before serving.
Note: Although the biggest cause for bitter lettuce is temperature, along with the other possible reasons listed above, additional factors such as one’s region, current growing conditions and even variety can all play a role in the bitterness of lettuce plants.