zucchini turning yellow and rotting

Why Your Zucchinis Are Turning Yellow And Rotting (And 7 Other Zucchini Issues With Rot Free Advice)


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When your zucchinis are turning yellow and rotting, it’s time to take action. Also called courgettes, zucchinis are grown for their edible fruits, and they are usually found in home gardens. Zucchinis’ flowers are also consumable, and they are occasionally fried. When growing your own zucchinis, you may have this question: Why are my zucchinis turning yellow and rotting?

One reason why your zucchinis are turning yellow and rotting is because of poor pollination. Another factor is Blossom End Rot which is caused by a lack of calcium in the fruits. When zucchinis are turning yellow (leaves), the highly likely culprits are usually diseases or insects and, at times, diseases caused by insects.


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Let’s dig in more on the causes to find out why zucchinis are turning yellow and rotting, as well as on how to prevent such things from occurring. Some other concerns about growing zucchinis are also addressed in this article.

Zucchinis Are Turning Yellow
There’s a big difference between a yellow zucchini, and a green zucchini turning yellow. Make sure you don’t just have yellow zucchini before treatment.

How Do You Stop Blossom End Rot On Squash?

Even though blossom end rot is frequently deemed a problem affecting tomatoes, it affects squash plants. Squash blossom end rot is avoidable, and there are several tips to try for blossom end rot treatment. Remember that you must conduct these remedies before squash blossom end rot emerges; otherwise, you cannot correct the fruit once it rots. If your zucchinis are turning yellow already, it may already be too late for those particular fruits of the plant.(4)

The single most significant thing to do to stop blossom end rot is maintaining a consistent soil moisture level routine. This practice can be done through watering during dry weather, as vegetables need between one (1) inch and 1 ½ inch of water every week from irrigation or rainfall for them to grow well. When there’s a shortage of rainfall, water them once or twice a week. (5)

It is essential to water uniformly — not too much or too little. If the squash undergoes extreme variations in the amount of water it receives, it might not absorb the calcium it needs at the critical period when the fruit is being formed. Otherwise, the zucchinis are turning yellow or rotting, so it’s best to water with a pattern.


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Before planting, add a suitable variety of fertilizer — a low nitrogen fertilizer to the soil. Putting too much nitrogen will create a growing imbalance between the leaves and the roots. If the foliage grows too quickly, the squash does not have adequate roots to consume the fruit’s calcium.

Another way to stop blossom end rot on squash is to add lime in order to balance the soil pH or soil reaction if it’s too low. For optimum calcium absorption, the soil pH value must range between 6.0 and 6.5. Soils with pH values less than 5.5 are considered resolutely acidic.

Soil pH Testing Tip: Pick up a battery-free multi-tester and keep it handy so you can check and ensure your plant’s conditions are doing well. I use the Alkey Soil Moisture Meter – it’s a 3-in-1 unit I grabbed off Amazon and it works great. A good tester helps me when my zucchinis are turning yellow, so I can determine the cause and correct it.

Using gypsum, which is a soft sulfate mineral, will aid in adding calcium to the soil. Doing so will cause that nutrient to become more readily available. When the nutrient is more readily available you are less likely to face a situation when zucchinis are turning yellow. (4)

Once there’s a squash with blossom end rot, remove the affected fruit immediately and apply a calcium-rich foliar spray on the plant. This action will guarantee that the next batch of squash the plant forms will have ample calcium to grow properly. The reasons why there are squash end rots are pretty simple, and blossom end rot remedies are easy enough when the source of the problem is identified correctly.

organic round zucchini growing in Farmer Jer's garden in July of 2020
Several of the zucchinis had to be removed from this round zucchini plant growing in Farmer Jer’s garden in 2021 due to blossom rot. I said to my wife “My zucchinis are turning yellow!” and she ran over to the library to start research!

Why My Zucchinis are Turning Yellow And Rotting?

When your zucchinis are turning yellow and rotting it can be an unfortunately common problem for gardeners. There are a couple of answers as to why this rotting is happening, and some are more serious while others may be easy to address. You have to figure out well the reason behind it so you can provide the correct remedy.

One of the main factors of zucchinis turning yellow and rotting is pollination — poorly pollinated plants develop fruits that become yellow and drop, horticulturally known as fruit abortion. It is common for such problems to occur if the plants are not being pollinated. Generally, pollination is carried out by insects that are on a search for nectar.

In order to ensure insect pollination, gardeners should grow other plants near zucchinis. Sometimes the best thing to do when zucchinis are turning yellow is ensuring they have flowering friends nearby. This type of gardening design is known as “companion planting,” which can attract more pollinators to your zucchinis, and some good companions for zucchinis include oregano, nasturtium, and marigold. You can also try to hand pollinate your zucchinis which is usually the most certain way. (2)

Another major cause of why your zucchinis are turning yellow and rotting is Blossom End Rot, which acts on the squash family and chilies, cucumbers, eggplants, and tomatoes. The blossom end rot is due to a lack of calcium in the fruits, which is not always caused by soil deficiencies. Calcium inadequacy does not only result in yellow and rotting fruits but also small growth and malformed foliage.

As for zucchini leaves that are turning yellow, you might still be able to save your plants under some conditions. Either diseases or insects probably trigger this issue, and on occasions, by diseases caused by insects. Cucumber mosaic virus is among the more usual diseases brought by the presence of insect pests.

The disease, cucumber mosaic virus, generally exhibits itself as yellowing zucchini leaves along the veins. Sometimes it shows you when the zucchinis are turning yellow, but mostly it starts on the leaves. The culprit of such is the aphids feeding on the foliage’s undersides, and these tiny insects transmit the virus — resulting in overall stunted growth and poor fruit development. Regrettably, once the plants are infected, you can’t cure them anymore.

Gardeners can cease the progress of the disease by eradicating any infected plant parts. Preferably, check out your zucchinis for aphids before they are infected. It would be best to remedy any signs of these insects right away with insecticidal soap or neem oil. (6)


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Need to clear out some aphids or other pests? I used some organic soap and sprayed the pests. They came back a few days later, so I used some neem oil spray and that cleared them out. I’m not a fan of spraying anything and would normally order ladybugs, but alas, this year the ladybugs are all sold out. So, try using organic sprays that are safe for your veggies. Pests like aphids are a problem when your zucchinis are turning yellow. Too much stress and the plant will wither and die.

Another insect pest that makes the zucchini leaves yellow is the spider mite, as it sips the saps from the foliage. In addition, a fungal disease called Fusarium wilt can also infect your zucchinis, and fungicides are ineffective in such cases. They are being carried by cucumber beetles that affect either cucumbers or zucchinis.

The Top 3 Frequently Asked Questions About why Zucchinis are Turning Yellow And Rotting

How can I prevent my zucchinis from turning yellow and rotting?

There are several ways to prevent you from having to say ‘My zucchinis are turning yellow and rotting’. First and foremost, ensure proper pollination. Zucchinis that are not pollinated well will bear fewer fruits and fruits which turn yellow.

Careful garden planning can make your zucchinis have successful pollination; consequently, for you to have an abundant yield. Plant your zucchinis in full sun, placing them 12-15 inches apart to coax flowering and insect pollinators. One good way to enhance pollination rates and quality is by interplanting your zucchinis with blossom annuals that attract bees and other significant pollinators.

Another ideal way for your zucchinis to have proper pollination and avoid becoming yellow and rotting is to take matters into your own hands. As zucchini pollens are somewhat sticky, they don’t usually blow from one flower to another or by just shaking the plants. You must try to do the simplest hand-pollination method — ensuring that you’re not wasting your time by making it your first chore of the day. (3)

Blossom End Rot is a primary reason why your zucchinis are turning yellow and rotting. You can avert this from happening by ensuring that your zucchinis have sufficient calcium, as this nutrient holds the cell walls of plants together. Way before your zucchini plants are grown, add adequate calcium (garden lime and Epsom salt) to the soil. (2)


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In order to prevent yellow leaves on your zucchinis, one sure way is to plant disease-resistant varieties. Additionally, ensure that the bed is prepared well and modify the soil with compost or other organic matters before planting. You have to guarantee that the general soil structure is refined — lighten it if it’s dense or has heavy clay and upgrade drainage.

What are other common zucchini growing problems?

As gardeners, particular plant problems should be spotted as early as possible. Be sure to check out your zucchinis regularly and keep an eye on whatever potential problem they may have. Aside from when your zucchinis are turning yellow and rotting, there are other common problems you may encounter when growing such plants:

  1. Failure of seedlings to germinate

Zucchini seeds might fail to sprout if they are planted too deep, or the soil quality is relatively poor. It can also happen if there’s too much or too little water and if it’s too cold.

  1. Failure of seedlings to thrive

The seedlings have germinated; however, they are not looking outstanding. The seeds may seem discolored, like they’ve been soaked in water, and this is caused by fungus or mold.


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  1. Misshapen leaves

Zucchini leaves might start to curl or become deformed or distorted. When this happens, look for aphids or other pests and spray your plants well.

  1. Wilting parts

When some parts of zucchinis are wilting, there’s a pest problem in the garden. Make sure to sprinkle pest control, reapplying it whenever it rains or after the plants are watered.

  1. The powdery coating on leaves

White, powdery spots forming on leaves will eventually scatter until the entire zucchini plant seems like it has been sprinkled with flour. This disease is due to a fungus and can be addressed by using a sulfur-based fungicide.

  1. Falling off of flowers

The most common cause of flowers falling off the vine is that male ones had released their pollens and also because of poor pollination. In this case, ensure that zucchinis are adequately pollinated.

  1. No fruits

Zucchinis, having formed flowers yet with no fruits, is due to a pollination problem. Guarantee proper pollination by attracting more insect pollinators or by conducting hand pollination.

How can I make my zucchinis grow well?

In order to ensure your zucchinis can grow well, sow them in full sun. They prefer well-drained soil; consequently, it would make them happier if you plant them in hills or raised beds. Before planting, add aged compost to the sowing hole and ensure that your zucchinis have ample space. (7)

Zucchinis are frequently attacked early by pests such as cucumber beetles. Safeguard the seeds by putting floating row covers until they start to flower because they grow on short vines, train vines to stakes using horticultural tape or cloth ties, and make the fruits clean and enhance air circulation.


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Remember, if your zucchinis are turning yellow, use a process of elimination and try to optimize the soil and watering conditions first before doing anything more drastic.


  1. Zucchini plant and vegetable, Cucurbita pepo variety https://www.britannica.com/plant/zucchini
  2. zucchini Turning Yellow And Rotting https://growing-guides.co.uk/zucchini-turning-yellow-and-rotting/
  3. Why Do My Zucchini Turn Yellow While Growing? https://homeguides.sfgate.com/zucchini-turn-yellow-growing-102317.html
  4. Squash Rotting On End: Squash Blossom End Rot Causes And Treatment https://www.gardeningknowhow.com/edible/vegetables/squash/squash-blossom-end-rot-causes-and-treatment.htm
  5. Why Are My Squash Rotting? https://pender.ces.ncsu.edu/2020/03/why-are-my-squash-rotting/
  6. Zucchini Leaves Turning Yellow: Reasons For Yellow Leaves On Zucchini https://www.gardeningknowhow.com/edible/vegetables/zucchini/yellow-leaves-on-zucchini.htm
  7. Zucchini Growing Problems: Troubleshooting https://harvesttotable.com/zucchini_growing_problems_trou/

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