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Why Is My Lettuce Bitter? Here Are 4 Likely Reasons!

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After months of tenderly caring for your homegrown lettuce, the time for harvest has finally come. Anticipating a wonderful mouthful of crisp, delicious lettuce, you’re dismayed to find your lettuce tasting bitter. How frustrating! Why is my lettuce bitter?!

Bitterness in lettuce can result from many factors, including the cultivar, growing conditions, and storage methods. In this article, we will explore the common causes of bitter lettuce and provide tips on how to prevent it from happening in the future.

Sound good?

Then let’s continue!

Why Is My Lettuce Bitter?

planting lettuce seedlings in the backyard garden on a beautiful day
Few things are worse for a salad garden than bitter-tasting lettuce! But why does lettuce turn bitter in the first place? Usually, lettuce turns bitter due to hot weather, a lack of moist soil, and early bolting. There are also a few little-known reasons your lettuce can lose its delicious, sweet taste. Let’s brainstorm several of them, shall we?

Bitter lettuce can be a real downer but don’t despair – we’ll run through the reasons and solutions so you can grow delicious lettuce.

Lettuce is a cool-weather crop and doesn’t thrive in hot summer weather. High temperatures and direct sunlight can cause it to taste bitter, so try planting lettuce in partial shade or using shade cloth.

Nutrient deficiencies can also play a role in the bitterness of lettuce, as can water stress. Fertilize regularly and provide excellent garden soil – and water to combat these issues.

Bolting lettuce tastes bitter, too. Bolting is a critical issue in warmer climates. When lettuce bolts (goes to seed), it’s putting all its energy into producing seeds. It’s no longer focussing on its juicy green leaves. Bolting is a natural survival instinct, but unfortunately, once it bolts, it’s mainly used for seed saving – not eating.

Finally, pests and diseases can cause damage to lettuce and add a yucky bitter taste.

So, there you have it! Environmental conditions, nutrient deficiencies, pests, diseases, and the natural bolting process can all contribute to the bitterness of lettuce. Let’s look into each problem in detail and see what we can do to fix the issue.

1. Hot Temperatures

growing delicious and healthy lettuce in lovely and lush garden soil
Lettuce is a cool-weather crop that loves growing in 60 to 70-degree (Fahrenheit) weather. Lettuce grown in warm temperatures exceeding 75 degrees can turn bitter and lose its sweet taste. The reason is that in hot temperatures, lettuce bolts! When lettuce bolts – it stops focusing on vegetative growth and instead starts producing lettuce seeds. In other words – bolting lettuce tastes bitter. Luckily, we’ve had some luck reducing the bitter taste by washing and chilling the bitter lettuce leaves in a fridge. Give it a try!

Lettuce loves cool temperatures and tastes best when grown in the sixties. But summer heat can wreak havoc on lettuce, making it taste tart. When temperatures rise, lettuce tends to wilt and become stressed, which triggers a natural process called bolting. Bolting is when the lettuce plant begins to produce a flower stalk and sets seed – changing the flavor of the leaves.

Providing partial shade is a great way to keep your lettuce cool and prevent bitterness. If hot, direct sunlight hits your lettuce all day, consider shading it with a cloth or other cover to reduce the heat it receives. Shading will help keep the lettuce leaves chilled and sweet.

Secondly, watering is crucial to help keep your lettuce cool. It’s best to water your lettuce early in the morning or at night when the temperatures are slightly nippy. Frequent watering prevents the leaves from burning and wilting in the scorching heat. Remember to water consistently to ensure the soil stays moist.

Choosing heat-resistant lettuce varieties is also essential. Some lettuce varieties thrive in cooler weather and don’t hold up well in hot temperatures, making them prone to bitterness. Opt for heat-resistant varieties like arugula, romaine, and butterhead lettuce which can withstand heat better.

Finally, mulching is another way to keep your lettuce cool and prevent bitterness. Adding a layer of organic matter like leaves, straw, or woodchips to the soil helps sustain water and the sun out, creating a chillier environment for your lettuce to thrive.

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2. Lack of Water

growing lots of delicious romaine lettuce in a greenhouse
Here you see some beautiful Romaine lettuce growing inside a well-hydrated greenhouse. We don’t usually grow in greenhouses – but lettuce is the perfect greenhouse crop. Remember that lettuce is shallow-rooted, so it loves growing with damp moisture. (Maintaining consistently moist soil levels is straightforward in the greenhouse. That’s why we say lettuce is one of the perfect greenhouse crops.)

We want to mention a lack of water again because lettuce needs moisture. And lots of it! A common culprit of bitter lettuce is a lack of water. When lettuce plants don’t get enough water, they can become stressed and produce bitter leaves. Sometimes, the same issue results from overwatering, but it’s not as likely.

Symptoms of water-stressed lettuce include wilted or droopy leaves and leaf edges that turn brown or crispy. And a generally sad-looking plant.

Consistently watering your lettuce is the best way to avoid bitterness caused by water stress. The best way to water lettuce is directly on the soil or with a gentle misting from above.

Proper drainage is also vital to prevent water from oversaturating the soil. Too much water can cause root rot. Ensure your lettuce gets planted in well-draining soil with plenty of drainage holes in your container or raised bed.

3. Nutrient Deficiencies

tasty green and red lettuce ready for a homemade sandwich or salad
Luckily – growing sweet-tasting lettuce is surprisingly easy. Lettuce loves moisture, fertile soil, and cool temperatures in the sixties. It hates salinity, warm temperatures, and dry conditions. Regarding lettuce nutrients – we usually don’t go overboard when amending our salad garden’s soil. And we only use organic fertilizers, never synthetic varieties. Our favorites are chicken, cow, & sheep manure, worm castings, and natural compost. Work the organic compost into the garden soil a month before transplanting your lettuce for a nutrient boost. (We also found an excellent guide teaching how to use compost manure. The guide contains a chart sharing how much fertilizer or compost you need in various situations. We printed the chart for easy reference!)

Lettuce needs certain nutrients to grow happily and healthily. Nitrogen, potassium, and phosphorus are the vital trio every lettuce plant needs in abundance. Sometimes, lettuce can suffer from nutrient deficiencies, which can cause the leaves to become bitter-tasting.

Luckily, this is one of the less fussy problems to solve. It’s essential to fertilize your lettuce regularly with a good-quality fertilizer. I often fertilize my lettuce plants (and all other leafy greens) every two weeks with a fertilizer tea. I prefer an organic fertilizer with equal amounts of nitrogen, phosphorus, and potassium (NPK), such as 10-10-10 or 5-5-5.

We love organic fertilizer the best. Lettuce also responds well to a foliar fertilizer – a liquid you spray onto the foliage rather than applying to the soil. I find most leafy plants love foliar feed.

It’s essential to read the instructions on the fertilizer packaging. Some may be slow-release, and you may only need to apply it every few months. Others may have a weekly application rate.

Timing is vital, too. It’s best to apply fertilizer when the soil is moist and as the plants are actively growing. Avoid fertilizer application when the weather is hot and dry – doing so can burn the plants. Be careful with young seedlings, as it’s surprisingly easy to over-fertilize.

Don’t neglect nutrient deficiencies, or you could end up with a bitter head of lettuce no one will want to eat.

4. The Variety

green cos lettuce flowering and producing seeds in the garden
Here you see some Green Cos lettuce flowering prematurely in hot weather. This bolting lettuce will taste bitter! Luckily – we’ve noticed that some lettuce cultivars can handle the heat – and taste less tart overall. We’ve had the most luck with Saladbowl, Green Leaf, Buttercrunch, Crisphead, Red Leaf, Romaine, Saladbowl, and Butterhead. These cultivars seemingly withstand fast bolting and bitter tastes more than others. We also advise investigating which lettuce cultivar grows best in your region – as your results may vary! And finally – Crisphead lettuce is probably the worst salad crop for growing in warm temperatures. It bolts tremendously fast – and early!

There are many lettuce varieties – some are more prone to bitterness than others. Look for lettuce varieties described as sweet or mild to avoid a bitter flavor. In warmer climates, choose open-leaf varieties – not heart-forming types.

Open-leaf varieties are less likely to bolt, and you can start harvesting leaves when the plant is very young – great for a lunchtime sandwich!

  • Try growing lettuce specifically bred to be less bitter, such as “Buttercrunch” or “Jericho.”
  • Butterhead lettuce, also known as Bibb lettuce, is incredibly tender and has a milder flavor than other types. It’s perfect for salads or sandwiches.
  • Romaine lettuce often has a slightly bitter taste. It has sturdy leaves that hold up well in salads or as a substitute for bread in wraps.
  • Leaf lettuce is a frilly, delicate lettuce commonly used in salads. It comes in different colors and has a mild, sweet flavor.
  • Mesclun is a mix of different lettuces and greens that include baby spinach, arugula, kale, and radicchio, to name a few. It has different textures, flavors, and colors, making it perfect for complex salads.
  • Finally, iceberg lettuce is the most common type found in grocery stores. It’s crunchy and lacks a potent flavor, making it great for sandwiches and burgers.

Each lettuce cultivar has unique characteristics. You can choose a yummy variety for every occasion – whether you want a mild, sweet flavor or a slightly bitter crunch.

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02/14/2024 02:21 pm GMT
butterhead lettuce freshly harvested from garden

How to Prevent Bitter Lettuce

Yield: Sweet, Juicy Lettuce

Lettuce is generally easy to grow in your garden. However, it can become bitter, which is ultra disappointing! But don't worry; there are ways to grow non-bitter lettuce. Here are some steps to follow.

Materials

  • Non-bitter lettuce seeds (described as 'sweet' or 'mild'. Buttercrunch and Jericho are great.
  • Fertilizer suitable for lettuce. Balanced NPK.
  • Heat protection. (Partial shade or shade cloth)

Tools

  • Watering can or irrigation system.
  • Secateurs or scissors for harvest.

Instructions

  1. Buttercrunch lettuceChoose the right variety of lettuce. There are many varieties of lettuce; some are more prone to bitterness than others. Look for lettuce varieties described as "sweet" or "mild" to avoid bitterness. Alternatively, try growing lettuce specifically bred to be less bitter, such as "Buttercrunch" or "Jericho."
  2. Plant at the right time. Lettuce prefers cooler temperatures, so it's best to plant it in the spring or fall when the weather is mild. If you plant lettuce when it's too hot, it can become stressed and produce bitter leaves.
  3. Water regularly. Lettuce needs consistent moisture to grow properly. The lettuce can become stressed if the soil dries out which will cause it to produce bitter leaves. Always water your lettuce regularly, especially during dry spells or hot weather.
  4. Fertilize regularly. Nutrient deficiencies can cause lettuce to become bitter. Use a balanced fertilizer (10-10-10, 5-5-5, or similar) regularly. Avoid high-nitrogen fertilizers, which can promote rapid foliage growth and bitterness.
  5. Protect from heat. Lettuce doesn't cope well with hot temperatures. Provide partial shade in the right position or use shade cloth to provide protection.
  6. Harvest at the right time. Lettuce leaves become bitter as they mature, so harvesting them at the right time is super important. Harvest the leaves when they are young and tender; before they become tough and bitter. You can also harvest the outer leaves of the lettuce plant first, leaving the inner leaves to continue growing. Once the plant bolts, the leaves become very bitter, so try to harvest before this happens.
  7. Store properly. After harvesting, store your lettuce in the refrigerator to keep it fresh. If lettuce leaves become wilted or dry, they can become bitter. Use your lettuce as soon as possible for the best flavor.

Conclusion

Thanks so much for reading our bitter lettuce guide. We know that growing salad greens is a lot of work – but hopefully, our tips make it easier.

With these tips in mind, you’ll be able to enjoy fresh, sweet-tasting lettuce even in the hottest months of the year!

Thanks again for reading.

And have a great day!

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