What Causes Bitter Cucumbers and How to Prevent it?

If you’re wondering what causes bitter cucumbers and how to prevent it, chances are you’ve grown cucumbers that had a bitter taste.

It’s no fun. You’ve just plucked that long awaited homegrown cucumber, eager to bite into the first one of the season, only to discover that your cucumber is unpleasantly bitter. It’s disappointing to say the least. We’ve had this happen too and will cover some of the causes and solutions.

Causes of Bitter Cucumbers

Too much stress can cause cucumbers to turn bitter. Stressed conditions are related to the growing environment and weather conditions. In fact, these factors are typically what causes crop stress and failure in general.

Stressed cucumbers create a bitter compound in much the same way that stressed humans produce more of the stress hormones cortisol.

Cortisol is designed to help us survive in much the way cucurbitacin is designed to help cucumbers survive stressful conditions. But, just as too much cortisol can increase stress and anxiety, too much cucurbitacin can create bitter cucumbers.

Stress Factors That Cause Bitter Cucumbers

• Heat – too hot
• Sun – not enough sunlight
• Water – a lack of water from dry weather or from uneven watering
• Soil – poor soil quality
• Variety of cucumber – some varieties are more prone toward bitterness if stressed in these ways

While any cucumber can become bitter under stressful growing conditions, some varieties are less prone to bitterness. So choosing non-bitter cucumber varieties will help insure your cukes are not bitter.

Choose Non-bitter Cucumber Varieties

• Aria
• Burpless Hybrid
• Burpless Sweet
• Chelsea Prize
• Chinese Snake
• County Fair 83
• Green Fingers Persian
• Holland
• Jazzer
• Lemon
• Marketmore 80
• Muncher
• Striped Armenian
• Summer Dance
• Suyo Long (or Soyo Japanese variety)
• Sweet Slice
• Sweet Success
• Wautoma

Choosing non-bitter cucumber varieties will help you to avoid bitter cukes. Burpless varieties are bred to produce fewer cucurbitacins and thus be less bitter. However, there are no guarantees. If growing any other than the specifically non-bitter gene varieties, optimize for the best possible growing conditions.

The best defense is to reduce the occurence of cucumber stressors listed above, to the extent possible.

Cucurbitacin can be found in many common garden plants, including zucchini and broccoli of the Cucurbita pepo and Brassicaceae families.^[1]https://en.wikipedia.org/wiki/Brassicaceae

A Little is Medicine, Too Much is Toxic

Cucurbitacins are tetracyclic terpenes with steroidal structures that are isolated from plants of the family Cucurbitaceae such as pumpkins, gourds, and cucumbers. Ancient peoples used cucurbits medicinally, but they also recognized their toxic properties. Medicinal uses included emetics, narcotics, and antimalarials.
SOURCE: ACS.org^[2]https://www.acs.org/content/acs/en/molecule-of-the-week/archive/c/cucurbitacins.html

Medicinal Benefits of Cucurbitaceae Plants

Cucumbers Are Beneficial for Health Issues Such as:

• inflammation
• cancer
• atherosclerosis
• diabetes

While more research is needed to sort this all out, it is known that Cucurbitacins have potent medicinal benefits, that can be toxic in large quantities. However, the quantity of Cucurbitacins in Cucurbitaceae plants is generally too small to cause harm via food consumption, and in fact can be very beneficial.
SOURCE: NCBI Cucurbitacins Study^[3]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4441156/

It’s no accident that “bitter medicine” is a term for many medicinal herbs and plants, such as dandelion leaves, have bitter properties that are a part of their healing properties.

What To Do With Bitter Cucumbers

Bitterness in cucumbers accumulates most in the leaves, skin and stem ends.

How to Reduce Bitterness in Cucumbers

• Peel cukes
  • Alternately, Cut of cucumber ends, then scrape a fork down length of the outside of the whole cucumber. Rinse
• Cut off and discard 1-2″ of the stem end
• Soak peeled cucumber slices in a little vinegar and salt
• Cut end off cucumber and rub it around the open cut end until you see a whitish foam. Repeat on the other end, then rinse off cucumber.
  • Alternately, slice cucumber lengthwise. Sprinkle with salt and rub open sides together until you see the white foamy substance. Rinse and enjoy… it’s said to be less bitter.

Never Give Up

Don’t give up. Each season in the garden is about learning more and growing better… not bitter!

Beginner gardeners are sometimes baffled by how things they grow aren’t as perfect or as tasty as store bought. There are a number of reasons for this. Sometimes, it’s just that the taste is better and fresher but they’re not used to it. For instance, arugula, a.k.a. “rocket”, tastes much more tangy and peppery fresh from our garden than anything we buy. We think it’s delicious, but to someone not used to really fresh vegetables, the strong flavor might be overpowering at first.

The most common reason for bitterness in cucumbers is somewhat the same cause of bitterness in people: it’s from a lack of something.

The most common reasons for cucumber bitterness is either too much or too little of something.
~GardensAll.com

How to Prevent Bitter Cucumbers

PROBLEM: When it’s too Hot for Cucumbers

One of the most common causes for bitter cucumbers is due to heat stress. If a plant is stressed from heat, it may start producing more cucurbitacins, which will cause cucumbers to be bitter.

SOLUTION: Mulch

One way to protect cucumbers from heat is with mulch. Mulch helps keep plants warmer when it’s cool and cooler when it’s hot. So when it gets really hot, you could try piling up some cool composting leaf mulch, a la deep mulch gardening style. 

Best Temperatures for Cucumber

Cucumbers do best below 90℉/32℃, so if your temps get over the low to mid 90’s, cover with a cloche or grow in an area with afternoon shade.

PROBLEM: Uneven Watering of Cucumbers

Another possibility for what causes bitter cucumber is when a cucumber plant goes through alternating periods of drought and overwatering. The stress from this can cause the plant to produce bitter fruit.

SOLUTION: Drip Irrigation

Best solution to this we’re loving is the drip irrigation. So much better than the sprinklers, but if you need to go with a sprinkler for now, this is currently the best selling sprinkler on Amazon.

PROBLEM: Temperature Fluctuations

If the temperature fluctuates dramatically from one extreme to another over an extended period of time, the plant may start producing bitter cucumbers.

SOLUTION: Straw Bale Gardening and Hoop Covers

If you live in a zone with high fluctuations, you might try straw bale gardening and hoop covers to work with reducing the dramatic temp differences.

PROBLEM: Heredity

Perhaps the most frustrating reason why a cucumber is bitter is simple genetics. There is a recessive trait that can cause a plant to produce bitter fruit from the start. You may plant seeds from the same packet and treat them all the same, only to discover one of the plants produces bitter cucumbers.

SOLUTION: Choose Non-bitter Varieties

Like people, our vegetables need a good environment and ideal growing conditions. Try some of the non-bitter cucumber varieties such as those listed above.

The very best remedy for bitter cucumbers is ideal growing conditions.

Wisdom from the Community

Here’s a remedies from the GardensAll community.

“Mix one part milk with 2 parts water in a sprayer and spray plants. Old timey, but effective remedy for bitter cucumbers.”

We use a power sprayer when spraying a lot of plants or plant area.

Bottom line? Don’t give up! As in life, there are always wins and losses, failures and successes in the garden. The winner is s/he who doesn’t give up.

Cucumbers are a wonderful summer fruit (yes, botanically, cucumber is classified as a fruit!), that refresh salads, are essential to gazpacho, make awesome green juice, and of course… pickles! 

And, if you haven’t tried Mexican gherkins… also known as cucamelons, you might want to give those a go this season. We love them! And… when your cucumber crop is awesomely abundant, you can make fermented cucumbers, aka refrigerator pickles, and/or you CAN freeze cucumbers!

If at first you don’t succeed… grow, grow again!