Why Is My Lettuce Bitter? What To Do About It

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Did you excitedly harvest your lettuce crop then found it was too bitter to eat?

Ugh! This problem happened to me, so I researched to find out what went wrong.

To help you with bitter lettuce problems, read this guide that clarifies what chemical in lettuce causes bitterness and why your homegrown lettuce is bitter. I also offer creative ways to use bitter lettuce and explain if eating bitter lettuce will make you sick.

Once you understand more about bitterness in lettuce, you can make the changes necessary in your home garden to avoid this common issue!

What Makes Lettuce Bitter

Lettuce grown for commercial or personal use is from the species Lactuca sativa, a close family member to wild lettuces that naturally have a more bitter taste.

Why are they more bitter? Lactuca species of lettuce create a milky-looking latex inside a set of special cells called laticifers. The chemicals in this latex liquid contain the bitter compounds sesquiterpene lactones, which will overwhelm with bitter flavor when formed in abundance in lettuce leaves. 

Like radicchio and chicory, relative to lettuce retain more of these compounds in their leaves, and we expect them to have a bitter taste. Whereas in what we commonly think of as “salad” lettuce, we are programmed to expect a more sweet or neutral flavor as these varieties have become popular because of their lack of bitterness.

Unfortunately, all lettuces can become bitter when you grow them under specific conditions, as explained in the section below.

Why Is My Garden Lettuce Bitter?

Here are common reasons your home garden’s lettuce is bitter and ways to fix the problem:

Variety 

Don’t randomly grab packets of lettuce seed for your garden because you like the leaf color or the look of the foliage on the picture, as many of them are going to be bitter no matter how well you tend to them.

The lettuce varieties most home gardeners should select are romaine or crisphead (iceberg) that, when grown correctly, will have a pleasing and gentle flavor. Other common homegrown varieties that are only slightly more prone to becoming bitter are red leaf, green oakleaf, and butterhead lettuces. 

Stick with the two naturally sweeter varieties when you first start growing lettuce at home to increase your chances of success.

Once you grasp regional conditions and harvest times that impact bitterness, you can safely branch out to other varieties. 

Sun And Heat

Lettuce growing in hot, sunny conditions will trigger a process called bolting. Bolting is when the plant matures and sends out a stem that flowers. During this time, cells release more of the bitter compounds which flood the leaves.

Lettuce is a cool-season crop, but most beginning gardeners think late spring and summer are ideal times to grow all vegetables and are left with a bitter lettuce harvest when the plant goes through the bolting stage too soon. 

I love fresh salad all year and found it’s best to use a heavy mulch layer and use shade cloth over your lettuce beds during late spring and summer.

The fabric reduces the heat level enough to keep the crop tasty and extends the time it takes for the lettuce plant to mature and bolt, which means more leaves to harvest.

Water

Lettuce requires a ton of water to keep the leaves plump and sweet. Letting your lettuce dry out even a little bit, which you will notice by limp leaves or browning edges, will cause bitterness as it condenses the bitter chemicals inside the leaves that the water was offsetting.

The trick to keeping lettuce sweet is to monitor and maintain moisture levels rigorously with a soil tester, especially if you live in a warm, sunny region. 

Nutrients

When everything else looks okay in your garden (variety, shade, water), but your lettuce is bitter, chances are the crop is lacking in nutrients. Lettuce grows extremely fast and needs ample nutrients to develop properly. 

Always start with enriched garden soil and fertilize regularly throughout the growing season since the plant can quickly deplete soil nutrients. 

Disease

Lettuce hit by aster yellows phytoplasma disease will taste bitter. You can identify this issue by your whole plant looking misshapen, and the center of the leaves lose its color.

To prevent spreading the disease to other lettuce heads, you must remove the plant, surrounding soil, and any weeds in the plot as no pesticides can cure it. 

What To Do With Bitter Lettuce

So you have a batch of bitter lettuce. Now what?

Before tossing it in the compost heap or trash in frustration, try these suggestions that either reduce the bitterness or disguise it:

  • Soak the leaves in cold water with a touch of baking soda for 10 minutes. Rinse and soak in clear water five minutes more, then drain and eat.
  • Pick lettuce directly after a rain, when leaves are fully plump.
  • Cook or blanch the leaves.
  • Refrigerate for 24-48 hours before use.
  • Always pick lettuce in early morning after a late evening watering.
  • Add the leaves to smoothies where sweet fruit offsets the flavor.
  • Add to soups as a flavor enhancer.

Is Bitter Lettuce Safe To Eat?

Yes, it’s perfectly safe to eat bitter lettuce, but many people find it too unpalatable to swallow. 

The latex compounds that cause bitterness in cultivated lettuces are not toxic to humans. On the other hand, wild lettuces have much higher concentrations that are not poisonous but can induce gastrointestinal discomfort.

An interesting fact is that the Lactucarium found in all lettuces has a mild opiate-like effect on the brain that can cause sleepiness or a general sense of well-being.

In Summary

There is no need to worry about why my lettuce is bitter if you can prevent it from happening in the first place. Growing lettuce takes some trial and error, so even if you end up with a batch or two of bitter lettuce, put it to good use by following the tips above. 

Now that you understand what causes bitter lettuce and how to fix it, you can manage your next crops with confidence!