Here is a cucumber a few days away from being ready

What Makes Cucumber Bitter Tasting?

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Cucumbers are easy to grow and provide tons of fruit, so they sound perfect, but homegrown cucumbers can have a dark side, a very bitter dark side. If you have ever bitter 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 be made bitter by incorrect pollination and or stress during growth. Stress can be caused by a range of issues such as under watering, overwatering, damage to the plant and disease.

The Science

The bitter flavour in cucumbers is caused by a toxic chemical called cucurbitacin. This is normally 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 badly ill! This isn’t just a problem for cucumbers though, you can find the same issues in all marrows.

Heritage Varieties

Old school cucumbers produce both male and female flowers. Only the female flowers will ever provide fruit, but if pollinated the female flowers can produce incredibly bitter cucumbers. Trust me you will know if this has happened, the taste is unbearable and feels as if it is intense enough to burn your tongue. These cucumbers can make you ill due to the high concentration of cucurbitacin and need to go straight in the bin, sorry.

To prevent this you need to remove the male flowers as soon as they appear, this is a bit of a boring job but it does solve the issue straight away. That’s all well and good I hear you say, but how can I tell the difference between a male and female cucumber flower? Thankfully this is really simple and I have attached a couple of photos below so you can easily see the difference.


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.

Outdoor Varieties

While not commonly grown here in the UK there are outdoor cucumbers that can be grown through British summers. These varieties will normally have both male and female flowers but will not require the male flowers to be removed. Confusing I know. Seed produces will commonly leave growing instructions on the seed packet including whether the male flowers need to be removed or not. So make sure to read the packet if you are at all confused.

Modern Varieties

If you are growing modern F1 hybrids or seedless cucumbers then these tend to only produce female flowers so this just isn’t an issue for you. However, that does not mean they will never produce bitter or slightly bitter cucumbers. The reason I say slightly bitter here is that these modern varieties could be bitter but it will never be anywhere near as bad as a pollinated cucumber on a heritage variety.

So if with modern varieties the bitterness is not caused by pollination then what does cause it? Well simply put, it is caused by stress during the fruit production stage of the cucumbers life. What stress exactly? well, there are lots of different factors that can cause this, let’s have a quick run-through of them.

  • 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.

My cucumber setup
My cucumber setup

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