6 Reasons Cucumbers Turn Yellow And What You Can Do About It

Cucumbers are a fairly easy plant to grow and can produce large quantities of firm, green vegetables. However, your harvest will sometimes be blighted by an unsightly (and unsavory) yellow cucumber. Unfortunately, there are several reasons your cucumbers might turn yellow. 

Letting your cucumbers become overripe on the vine is the most common cause of yellow cucumbers. Lack of water can also be a culprit, as is the lack of nutrients in the soil. Other reasons can be diseases or poor pollination.

Some of these issues can be easily rectified, but in some cases, you are better off pulling the entire plant and starting over.  

So, If your cucumber plants start to show signs of trouble, like fruits turning yellowish or orange color, knowing how to fix yellow cucumbers will keep your harvest on track.

Keep reading to learn more about how to identify what is causing the issue and how to deal with it.

6 Reasons Your Cucumbers Are Turning Yellow On The Vine

There are many factors that result in yellowing cucumbers and each type has different solution.

Let’s find possible reasons why your cucumbers are turning yellow and what can be done.

1. You Are Growing A Yellow Cucumber Variety

1. A Yellow Variety

Perhaps this might be obvious, but are you growing a yellow variety? Some cucumber varieties have yellow or white coloured skin when they are mature.

If this is the case, your cucumbers are supposed to be yellow and you have nothing to worry about.

If one of your plants starts producing yellow cucumbers, then maybe a seed from a yellow variety ended up in the wrong seed packet. If this is the case, you have nothing to worry about, so sit back and enjoy your colorful diversity. 

However, if you are finding one or two cucumbers scattered amongst the plants then there is probably something else afoot. Keep reading to find out the culprit.

2. Overripe Cucumbers

2. Overripe Cucumbers

The most common cause of yellow cucumbers is that they are overripe. The cucumbers that we eat or buy in stores are considered horticulturally mature which is when the flavour and texture are ideal for eating.

If you leave a cucumber on the vine, it will continue to ripen to become botanically mature and will start to produce seeds for future propagation. As a cucumber becomes botanically mature, the chlorophyll in the skin fades and the cucumber turns yellow.

From an eating point of view, a mature, yellow cucumber is considered overripe. It will be very bitter and not worth eating. 

Size is not generally a quality looked for in cucumbers, though some varieties can grow quite large. Instead, cucumbers are grown for quality and quantity.

Since most cucumber varieties are ready for harvest in 50 to 60 days after transplant, the best way to avoid yellow overripe cucumbers is to check your plants every day and pick them continually.

There are a few things you can do with overripe cucumbers if you find any:

things you can do with overripe cucumbers
  • If they are not too ripe, they can still be edible when turned into pickles or relish. 
  • If the yellow cucumbers are too bitter to eat, remember that they are becoming botanically mature.
  • Leave them on the plant and let them fully mature and then you can harvest them for seeds for next year’s garden.
  • The last option is to put them in the compost.

3. Nutrient Deficiencies

Cucumber Nutrient Deficiencies

Cucumbers are heavy feeders, which means they need a lot of nutrients to grow healthy and produce lots of fruits.

Growing cucumbers in poor soil, or in the same spot year after, year can quickly deplete the soil by using up all the nutrients. If the plant is not fed sufficiently, it can produce poor-quality cucumbers that can turn yellow. 

Cucumbers generally do best when the soil has a balance of nitrogen, phosphorus, and potassium. Nitrogen is responsible for promoting healthy vegetative growth.

Phosphorus is vital to plant growth and helps with photosynthesis and converting starch to sugar, while potassium affects how water, carbohydrates, and nutrients move inside the plant. It is important to keep a high level of these three nutrients in the ground.

Here are suggestions to keep your soil healthy and your plants well-fed.

  • The best solution is to start the year off right by adding lots of compost or well-rotted manure. Compost will add a healthy mix of nitrogen, phosphorus, and potassium, but most composted plant matter is especially rich in potassium. Animal manure is high in nitrogen, especially from equines and poultry. If you are composting animal manure, keep wood such as shavings to a minimum as these can absorb valuable nitrogen. Cow manure is also fairly high in phosphorus, and ironically so are burned cucumber skins. Rock phosphate is another good way to add phosphorus to your garden, but make sure you follow the recommended application rates.
  • Crop rotation is another valuable tool in maintaining soil fertility. When you grow cucumbers in the same spot, again and again, they will continually strip the soil of the same nutrients each time. By moving your cucumbers and growing something else in that spot, it will give the soil a chance to rest and recuperate. A 3 to 4 year crop rotation is recommended to give the soil time to recover from the hungry cucumbers. 
  • Grow legumes, such as peas and beans near cucumbers, will improve the nitrogen. As they grow, legumes take nitrogen from the atmosphere and put it in the soil in a process called nitrogen fixation. The legumes first convert the nitrogen into a form that is accessible to other plants and helps rebuild the soil. 
  • If you start finding yellow cucumbers amongst your plants, it is too late to worry if you should have added enough compost. In this case, you might want to consider adding a good quality organic fertilizer. Try to find a fertilizer that is well balanced between nitrogen (N), phosphorus (P), potassium (K). This will be represented on the front of the package by three numbers, such as 10-10-10 which correspond to the N-P-K ratio of the fertilizer. Remember that fertilizer is a band-aid solution that only feeds the soil for a short time and will not build healthy soil in the long run. Avoid using conventional fertilizers if possible as they add toxic chemicals to the soil and groundwater.

4. Lack Of Water

Lack Of Water (1)

Not enough water, or inconsistent water, can cause the cucumbers to wither and yellow. Cucumbers have a shallow root system and insufficient watering means there won’t be enough moisture available at the level of the roots.

Be particularly careful if you are growing in containers, as the soil in pots will dry out faster than it does in the garden. As a word of warning, make sure you do not over water your cucumbers since this can lead to certain diseases as we will discuss below.

However, there are many ways you can conserve water consumption and still keep the soil around your cucumbers damp.

  • Again, adding compost to your soil is the most important thing you can do. The final product of decomposing plant matter is called humus, which adds organic matter which retains moisture in the soil and makes it readily available to the plants’ roots. Humus also keeps the soil from becoming water waterlogged by aerating the soil and improving drainage, which helps prevent diseases from taking hold. 
  • Applying an organic mulch is a great way to help the soil retain moisture. The mulch, such as straw, cardboard, or newspaper will not only trap moisture in the soil but will also slow evaporation by blocking the sun and keeping the soil cool. 
  • Green manures are also a great way to help with water retention. Green manuring is the practice of undersowing a plant around your cucumber plants. When these plants grow, they shield the soil like mulch and the roots will help hold water. Green manures can then be ploughed under where they will decompose and add organic matter to the soil which will further improve water retention and overall soil health.

5. Plant Diseases

5. Plant Diseases

In most cases, the health of a cucumber is tied to the health of the vine itself. Cucumbers are susceptible to a whole bunch of different diseases, and there are several that can cause your cucumbers to yellow.

If any disease is particularly bad in your area, consider growing a disease-resistant cucumber variety.

Cucumber Mosaic Virus

Cucumber Mosaic Virus

The Cucumber Mosaic virus is one disease that can lead to yellow cucumbers. When the Cucumber Mosaic virus attacks your plant, the cucumbers produced will be stunted and have yellow and white mottling. You can also identify this issue as the leaves on the plant will also have a yellow “mosaic” pattern, hence the name.

There is no cure for the cucumber mosaic virus and any affected plants should be destroyed before they spread the virus to the rest of your plants. Do not put the disease plants into the compost. 

However, there is still hope. This virus is spread by aphids and beetles, so stopping the insects can stop the virus.

Here are three ways to protect your plants from aphids and beetles and help prevent the Cucumber Mosaic virus.

  • Aphids are particularly attracted to weakened and stressed plants. Lack of water, soil imbalance, and nutrient deficiencies will not only cause yellow cucumbers, but they will cause the plant to be stressed and more susceptible to aphids infestations and disease. Keeping your plants healthy will eliminate a whole host of problems. 
  • Attracting beneficial bugs is the most natural way to eliminate problematic bugs, such as aphids and beetles. Again, companion planting is the answer. Most pollinators are also predatory, and they will begin devouring any undesirable bugs. Alyssum is a flower that adds beauty to your garden and also attracts numerous good bugs. Dill is another excellent companion plant (and it pairs well with cucumbers in the kitchen, too). Planting pungent plants, such as onions or garlic, can also help repel some bugs with their scent. 
  • Floating row covers are oftentimes necessary to protect your plants from invading insects. Place floating row covers over your young plants but be sure to remove them when flowers form or they impede pollination.
  • Beetle traps might be used as a last resort. But use them with caution as they can also trap predatory bugs, and inadvertently cause more harm than good. 
  • As crop rotation helps the soil replenish nutrients, so it helps the soil reduce sicknesses and disease. If you continually grow cucumbers in the same plot, the Cucumber Mosaic virus can take hold and you will be fighting a losing battle year after year. By rotating your crops, and not growing cucumbers in the same spot for 3 to 4 years, you are removing the host of the virus (the cucumber plant) and the disease will not be able to take over.

Bacterial Wilt

Bacterial wilt could be another culprit for your discoloured cucumbers. It is generally caused by the striped cucumber beetle.

  • Since the striped cucumber beetle can overwinter in the garden, crop rotation is again the first course of action.
  • Floating row covers can be used on your plants. Again, be careful not to interfere with pollination. 
  • In the end, go through your cucumbers and hand-pick off the beetles.

Fungal Diseases

Many fungal diseases can cause your plants to produce yellow cucumbers. Fungal diseases can usually be helped by improving air circulation around your plants.

  • Make sure your plants are spaced at least 40 cm (16 inches) apart to allow air circulation and keep the soil and plants dry.
  • Training the vines to a trellis can keep them off the ground with good air movement.
  • If you water your plants, make sure you water the soil and not the leaves. If you need to water regularly, a drip irrigation system might be the answer.

6. Yellow Cucumbers Are Often Caused By A Lack Of Pollination

6. Poor Pollination

A cucumber will form behind a female flower. If this flower is not pollinated, or if it is pollinated poorly, the cucumber will yellow, shrivel, and fall off the vine.

Here a few ways to ensure your flowers are pollinated.

  • Your garden will always thank you with a bountiful harvest if you attract as many pollinators as possible. Plant flowers or flowering shrubs, install bee boxes, put up a hummingbird feeder, never use pesticides or herbicides, and maybe even leave a few of those pesky dandelions to flower before you dig them out. There are countless ways to attract pollinators, and try and find one that best fits your garden plan.
  • If you do use floating row covers, make sure you remove them before the flowering stage so the pollinators can do their work.
  • If no pollinators can be found, it is up to you to do the job. Get a small paintbrush and “paint” the inside of each flower to replicate a bee

Conclusion

The joy of vegetable gardening culminates in the abundant harvest, yet this joy will be tainted as you watch your cucumbers turn yellow and become inedible.

Hopefully, this article has given you enough information to identify the cause of your unsightly yellow cucumbers, and you will be able to fight this battle naturally and make your garden a cornucopia of healthy, delicious food.

Updated on by Amber Noyes

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.