What Makes Cucumbers Bitter Tasting?

Cucumbers are easy to grow and provide a bounty of fruit, but homegrown cucumbers can have a dark side - a very bitter one. If you have ever bitten into an intensely bitter cucumber, then you will know just how disgusting they can be, but what causes this bitter taste? And once we know that, how do we stop it from ever happening again?

Cucumbers can become bitter due to incorrect pollination and/or stress during growth. A range of issues, including underwatering, overwatering, plant damage, and disease, can cause plant stress.

The Science

The bitter flavour in cucumbers is caused by a toxic chemical called cucurbitacin. This is usually found mainly in the leaves of the plant as a way of stopping grazing animals from chomping on its leaves. Sometimes, however, they end up in the cucumbers themselves in high quantities. This doesn’t just make the cucumbers taste bad but can also make you ill!

Reason (1) Pollinated When They Shouldn't Have Been!

Modern all-female cucumbers, and also some in betweeny hybrids, do not need pollination from male flowers to produce fruit. These are known as parthenocarpic plants (bit of a science lesson for you there!).

If a male flower pollinates these cucumbers, then they will create an abundance of cucurbitacin, rendering the cucumber inedible. Trust me, you will know when this has happened; it isn't just slightly bitter, it is overwhelmingly so. I experienced this when I first started out, and the taste was so bitter that it felt like it was burning my tongue. This is a good thing, as eating these cucumbers would make you ill!

This all depends on variety, so make sure you know what you are growing at the start of the season.

All female cucumbers shouldn't produce male flowers, but can do so under stress. If you see any male flowers, then remove them immediately.

Old school ridge, or outdoor cucumbers, produce both male and female flowers. These types of cucumbers do need the male flowers to pollinate the female flowers to produce fruit. You can see how this can get confusing quickly!

How To Tell Male & Female Flowers Apart

So, let me explain what is going on here. The female flower has a tiny fruit behind it just waiting to grow. Whereas the male fruit at the bottom has no fruit behind it at all. It is really easy to tell the difference between the two once you are up close and personal. You will also notice that the male flowers are growing in a sort of “clump” of flowers. This is another quick way of finding them.

Reason (2)

Your cucumbers being pollinated when they shouldn't have been is not the only reason why your cukes have become bitter; there are actually quite a few other causes that fall under one general umbrella of stress. These tend to cause slightly bitter cucumbers, whereas the pollination issue I talked about above causes very bitter cucumbers.

Well, simply put, it is caused by stress during the fruit production stage of the cucumber's life. When the plant is stressed it tends to create more cucurbitacin leading to that bitter taste.

• Too hot
• Too Cold
• Lack of nitrogen
• Pests
• Disease
• Damage

As you can see there are lots of different stresses that can cause this to happen. And with everything listed here, you may think cucumbers are hard to grow, but in reality, they really aren’t. Make sure they are always well watered and pruned and you will be 90% of the way there. If you use fresh grow bags every year you will have enough nutrients in the soil to keep them going for a full year too.

Pests and disease can be an issue but if you keep the cucumbers well pruned so there is lots of airflow then you can really reduce this risk.

Reason (3) Leaving Your Cucumbers Too Long

This is often the cause of bitter cucumbers for many people. They are left on the plant for too long and become very large, usually becoming bitter-tasting.

If your cucumber has become massive, then this is likely the cause of the poor taste. It is much better to harvest cucumbers regularly and at a smaller size than waiting for them to get huge.