The Cause of Bitterness in Lettuce


There are a lot of different kinds of lettuce and it is doubtless that people love to eat lettuce for everything from green salads to toppings on burgers. However, sometimes the lettuce has a bitter taste, even if it is home-grown. There are several reasons that this can happen.

Origin of lettuce

Though it isn’t clearly proven, the lettuce we use today mostly likely was derived from wild lettuce This is a plant that is edible and yet the flavor tends to be bitter, greatly owing to the milky sap or latex that it contains. The greater the amount of this fluid, the more bitter it often tastes. Through the years, head lettuce and the commonly sold types of leaf lettuce were bred and don’t have as much of the bitter latex. This is especially notable in head lettuce, which is often considered to be a bland lettuce. It is safe to say that for this very reason a lot of people like head lettuce for green salads.

One of the reasons for the bitterness, though, is simply that some plants might revert in part to their original ancestors. They can simply produce more latex, along with the bitter substances it contains. Domestic lettuces aren’t immune to reverting back to the originators.


Lettuce is a cool weather crop that loves plenty of water, in well-draining soil. All lettuce plants probably contain the bitter latex with head lettuce having among the lowest amounts, but with increased water, these substances can be diluted. Conversely, it would make sense that if the developing plants didn’t get enough water, bitterness would likely increase. The bitter juices also transport nutrients to the leaves and when the plant suffers from inadequate water, the plant often counters by sending as much of the nutrient-rich juices to every leaf. As a result, the leaves can become bitter.

High temperature

As already stated, lettuce is a cool weather crop. It doesn’t grow very well, as a rule, when the temperatures soar. High temperatures can stress lettuce plants. This is probably most notable in commercially grown lettuce. Stressed lettuce often produces more of the latex, which makes the lettuce bitter. This is a point of survival for the plant, since the plant can die if the leaves don’t have nutrients and moisture.


When lettuce starts putting out flowers and seeds, the plant generally puts most of its energy into creating the seeds that will be the next generation of lettuce. This isn’t uncommon for plants in general, but it means that the amount of the milky sap often increases in order for the plant to nourish the flowers and seeds. The sap is bitter in flavor, and it can start increasing before the blossoms are apparent. The result, if the lettuce is harvested at this time, it is usually bitter-tasting lettuce.

There are a lot of reasons for bitter-tasting lettuce. Some of them can’t be easily corrected, such as reversion to traits of wild lettuce. Most can be controlled, though, by such means as growing the crop in cooler weather and making sure that the plants get plenty of water. Avoiding stress when growing lettuce can help greatly, however this sadly isn’t always possible in commercially grown lettuce. Still, there are reasons that lettuce can end up tasting bitter.




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Posted in food and plants and tagged , , , , by with 2 comments.


  • Ah ha! Thanks for directing me to this article. I’ll try lettuce again. 🙂 I prefer the leaf varieties over head lettuce. It contains many more vitamins. I’m thinking that maybe it was too hot. We have very hot summers here. I’ll try it now that it’s spring. @rextrulove

    • rextrulove says:

      @kimdalessandro, it could have been the heat, especially if the lettuce bolted quickly. Around here, the biggest problem is improper watering.

      I prefer leaf lettuce, too. One big reason why is that I can pick however many leaves I want without pulling up the plant, so it just keeps furnishing me with leaves. 🙂

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