The first time I tasted bitter lettuce from my garden, it put me off lettuce for a long time. Interestingly, I had harvested some tasty, crispy lettuce before, so I knew something was wrong. I was even more concerned about my health and the effects of eating bitter lettuce.
It is safe to eat bitter lettuce from the garden because lettuce gets bitter due to exposure to high temperatures and not because it is contaminated. Other causes include insufficient water, fast maturity, insufficient nutrients, and Aster yellows–a plant disease that makes lettuce bitter.
I’ll discuss the causes of bitter lettuce in detail, how you can still enjoy your lettuce, and ways to keep your lettuce crispy and tasty.
Why Lettuce Becomes Bitter
When you first discover that the lettuce in your garden is bitter, your first reaction is probably to dispose of your harvest. However, you shouldn’t do so because your lettuce is safe for use.
It may not be as tasty as you had hoped, but it is not bad for you either. The reasons behind the bitter lettuce are not harmful, so you need not worry about becoming ill.
Lettuce becomes bitter for several reasons.
Here are some of them:
It’s a Cold-Season Plant
Lettuce is a cold-season plant best planted immediately after the last frost. Fortunately, these vegetables also mature quickly and will be ready for harvest within 30 days. The summer heat will turn the lettuce bitter if you wait too long.
High Temperatures
High temperatures cause lettuce to snap into maturity. It will start developing stalks and flowers, resulting in a change in taste.
Insufficient Water
Lettuce has shallow roots, so they need to be watered frequently. It is best to keep the soil moist, up to at least 2 inches (5.1 cm) deep.
To avoid overwatering, check the soil, and if it is dry, give your lettuce more water. If they don’t get all the water they need, they will become bitter.
Poor Soil Nutrition
Lettuce grows fast, but it will take longer to mature, or the growth becomes stunted without proper nutrients. Fertilize your garden at least twice a month. You can use liquid fertilizer or slow-release granules.
High Nitrogen Levels in the Soil
Over-fertilizing can also cause bitterness in lettuce. So, when feeding your lettuce, try not to overdo it, especially when using nitrogen-rich fertilizer.
Aster Yellows Phytoplasma
Aster yellows is a common disease that attacks lettuce and causes them to become bitter.
Signs of aster yellows in lettuce include severe yellowing of the leaves, brittleness, vein clearing, and rolling leaves. The middle leaves remain short and develop thickened stubs. The lettuce will also have stunted growth. It is still safe to eat the leaves that are yet to turn yellow.
Delayed Harvest
Some people pluck only enough leaves for their regular daily consumption from their lettuce plant, leaving the rest on the ground. The practice leaves the plant to bolt with age and heat, becoming bitter.
What to Do With Lettuce That Has Gone Bitter
Bitter lettuce is safe to eat, but it is not as palatable as delicious lettuce. Fortunately, there are some tricks you can use to minimize the bitterness in lettuce. You don’t need to get rid of all the lettuce, especially if you prepare salads often.
You can do the following to make bitter lettuce tastier.
- Pick your lettuce from the garden early in the morning.
- Water your lettuce in the evening to help it cool down after the hot day.
- Soak the lettuce leaves in cold water for 10-15 minutes, dry them, and refrigerate them for a few hours before use.
- Add rich flavors to your salad, such as salad dressing. You can also use lots of toppings, like cucumbers, cherry tomatoes, cheese, and croutons, to mask the bitterness in the lettuce.
- Soak the lettuce in cold water overnight before using them. If you need to make a salad immediately, you can add ice cubes to make the water colder.
- Cook the lettuce. You can mix it with other greens, such as spinach. You can even make lettuce soup or stir-fried lettuce.
- Soak lettuce in water and add baking soda for a few minutes. Rinse the leaves and soak in cold water for a few minutes. Taste the lettuce. If it is still bitter, soak the leaves again until the lettuce is more palatable.
- Refrigerate the lettuce for 24-48 hours before using them.
If you have a large garden of lettuce that has gone bitter, you can also leave them in the garden. Allow the lettuce to flower and go to seed. Lettuce seeds take a long time to mature, but the blooms attract pollinators.
You can also use the bolted lettuce to trap pests, such as slugs, aphids, and snails.
How to Prevent Bitter Lettuce
Although bitter lettuce is sometimes due to fast maturity and it is impossible to fight nature, you can take measures to delay bolting in lettuce.
These tips will help you keep your lettuce from going bitter quickly:
Mulch Your Garden
The heat in the soil alerts lettuce that it is summer, time to mature and start producing flowers. Mulching will keep the soil cool, and it will help retain moisture in the soil for longer. The roots will feel cooler and will assume it is still spring, so the lettuce is unlikely to bolt and become bitter.
Interplant the Lettuce With Taller Crops
You can also keep the lettuce in your garden cooler by practicing companion planting. Crops taller than the lettuce will shield the lettuce from the scorching sun, especially during summer. Asparagus and tomatoes are examples of plants that provide natural shade for lettuce.
Add Wood Ash to the Soil
You can confirm the nitrogen levels by testing the soil. If the bitter lettuce results from high nitrogen levels in the soil, you should add wood ash to the soil.
Besides wood ash, you can also mulch your garden with dried wood or sawdust. They break down the nitrogen and suck it from the soil.
Follow The Required Growing Conditions
Before planting lettuce, you need to know the ideal growing conditions for this plant. This is one of the best ways to ensure you grow delicious lettuce without the bitter taste.
Basic growing conditions for lettuce include:
- Use slightly acidic, loamy soil with a pH level 6.0-6.5.
- Lettuce grows best in containers or raised beds.
- The optimum soil temperature ranges from 60-80 °F (15.5-26.6 °C). Lettuce may still grow in high temperatures, but the seeds will not germinate when the soil temperature is higher than 95 °F (35 °C).
- Plant lettuce seeds ⅛-¼ inch (0.32-0.64 cm) into the soil. Alternatively, lightly cover the seeds with soil or compost. These seeds need light to germinate. Planting them too deep may interfere with the germination process.
- Keep the soil moist but not soggy.
If your area experiences higher temperatures or if the growing conditions are unsuitable, you should:
- Plant in a shaded area.
- Use containers for easy movement to shady areas.
- Shield the lettuce from the sun using shade cloth.
Plant Heat-Resistant and Slow Bolting Lettuce Varieties
If you wish to have lettuce during summer, or if your region is not cold enough to grow delicious lettuce, you should consider planting heat-resistant lettuce.
Lettuce falls under four main categories.
- Crisphead or Heading
- Romaine or Cos
- Butterhead
- Loose-leaf
| Lettuce Categories | Features | Heat-resistant Varieties |
| Crisphead/Heading |
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| Romaine/Cos |
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| Butterhead (Boston & Bibb) |
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| Loose-leaf |
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Of all the lettuce categories, Crisphead varieties are the least tolerant to heat. Even though some types are said to be heat-resistant, they are not as forgiving as those in the other categories.
This video shows what you can do to eat lettuce during summer:
Signs Your Lettuce Is Bolting
Lettuce sometimes becomes bitter before you notice any signs of bolting. Lettuce will thrive within the optimal temperatures. When the temperatures go too high, the lettuce will show signs of bolting.
When a lettuce bolts, it goes into seed. Instead of using its energy to produce juicy leaves, it focuses on seed production.
The signs to look out for include the following:
- The lettuce grows upwards instead of forming a firm head.
- The lettuce leaves space out like kale.
- The central stalk becomes longer.
- The lettuce starts flowering.
- The leaves become bitter.
Conclusion
Bolting is a natural growth process in lettuce. High temperatures signify a change in season from spring to season, usually alerting the lettuce that it is time to go to seed. If you plant your lettuce in the wrong season, or if the conditions don’t support lettuce growth, expect to harvest bitter leaves.
Fortunately, you can reduce the bitterness and make your lettuce tasty.
