Why Does My Lettuce Taste Bitter?

Have the temperature risen above 80 degrees Fahrenheit?

Do you water your lettuce regularly?

Did you provide afternoon shade for your lettuce?

Did you fertilize your lettuce?

Are the leaves of your lettuce also deformed and discolored?

Did you leave your lettuce in the ground for several days after it had reached full size?

Did you store your lettuce near fruits after harvest?

Lettuce is known as a cool-season vegetable and thrives at temperatures between 60 and 70 degrees Fahrenheit. When temperatures rise above 80 degrees, the plant snaps into maturation mode and bolts — sends out a stalk and flowers. It’s during this process that bitter lettuce is produced. As a preventative measure, always plant lettuce during the cool spring and late summer to early fall to ensure that your crop receives ideal temperatures.

Too little water can cause bitter lettuce. The large, flat leaves need a large amount of water to remain full and sweet. Brown leaf edges are a sure sign that your lettuce is thirsty either from lack of water or root damage from close cultivation. Water regularly and well. Don’t let the bed become completely dry.

Lettuce is a full-sun to partial shade plant. Partial shade, especially during the warmest parts of the day, safeguards your lettuce crops and helps them from taking on a bitter flavor. Use taller crops in your garden to shield lettuce from full, direct sunlight.

Lettuce needs to grow fast. Without proper nutrients, growth becomes stunted, and bitter-tasting lettuce is the result. Fertilize regularly, but don’t overdo it. Some studies suggest that bitter lettuce can also be the result of too much nitrogen.

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. Not much to do if the plant gets this disease, except removing and discarding it.

The time when you harvest your lettuce crop plays a big part in flavor. Once lettuce reaches its full size, it is ready for harvest. Young, tender leaves have the best flavor. Lettuce that is allowed to remain in the garden past harvest time becomes bitter and woody in taste.

Never store lettuce in the same drawer with apples, pears, or bananas, as these fruits release a gas that causes lettuce to quickly turn and spoil. If you notice a bitter flavor in recently harvested lettuce, place it in the refrigerator at 32 degrees Fahrenheit and 96 percent humidity for two days. Afterward, some of the bitterness should have dissipated.

Some varieties of lettuce like "Boston" or "Butter" are highly susceptible to taking on bitter flavors if growing temperatures are not ideal. Chose varieties like “Romaine,” “Buttercrunch,” “Ruby,” “Salad Bowl” and “Ithaca” lettuce that tolerate heat well and resist bitterness.