Why Zucchini Plant Leaves Turning Yellow?

Zucchini leaves are one of the most versatile plants that a home gardener and plant enthusiast can ever decide to grow in their backyard. If you are one of them, then you must be aware of the problems that come along with growing zucchini plants.

One of these is chlorosis, or the zucchini leaves turning yellow. While some people know how to tackle this situation, most of them remain aloof of the causes that contribute to these plant leaves turning yellow and the solutions that follow.

While there can be a lot of reasons why your plant leaves turn yellow, some of the most prominent of them arise from nutritional deficiencies of manganese, iron, and sulfur. Not many people are aware of this fact, making them turn a blind eye towards these important dimensions of their plant.

However, the answer to why your zucchini plant leaves have started turning yellow cannot be sufficed in a few lines, and requires a much in-depth analysis. Without any further ado, let us explore all the possibilities.

Why Zucchini Plant Leaves Turning Yellow?

Here are some of the most common reasons why your zucchini plant leaves have decided to turn yellow all of a sudden. Analyzing your plant problem is important since it helps you adopt a relevant treatment strategy accordingly.

Inadequate Sunlight

Inadequate sunlight usually has a lot to do with the lack of sunlight that is given to the plant, as opposed to the excess of it. When your zucchini plant does not receive proper sunlight, it becomes difficult for the plant to prepare food due to the lack of chlorophyll, required for photosynthesis.

On an average, a zucchini plant needs approximately 6 to 8 hours of sunlight to thrive and grow. It gives the plant enough time to produce chlorophyll and further food, thereby giving the plants their original colour.

Nutritional Deficiency

As mentioned in the beginning of this article, nutritional deficiencies contribute to yellowing of zucchini plant leaves to a great deal. Absence of nutrients like nitrogen, calcium, potassium, sulfur, and magnesium or the improper absorption of them by any part of the plant can have detrimental effects on the health of the plant.

Not only this, but a very slight chemical composition imbalance in the nutrient profile of your soil can contribute to chlorosis or yellow leaves of the zucchini plants. To get the most accurate profile of which nutrient is to blame for the underlying situation of your plant, a lab test is recommended.

Check this out: Is Cow Manure Good for Potatoes?

Improper watering techniques

Improper watering techniques include watering your plant either too much or too little, and this may be one of the most common mistakes that is undertaken by anyone. It is difficult to analyze the exact watering needs of your plant, but with experience and the right set of skills, one can easily achieve it.

Many people indulge in the practice of overwatering, thinking that it can curb the problem of under watering in their plants. However, the process of transpiration barres it from happening, therefore contributing to plant dehydration eventually.

Check this out: How Often to Water Cabbage?

Root damage

The root system is most important for any plant. A damage to the roots is directly observable in the form of yellow leaves of the plant. When the roots are damaged, they lose the ability to absorb adequate nutrients, thus making it difficult for the plant to survive. A key result is the dying leaves.

Some events that can stimulate root damage in zucchini plants include the recent transplantation of plants to a new location, or the rigorous digging of soil very close to the plant base.

A disappointing news is that root damage cannot be readily treated naturally. All you can do is give your roots enough time to recover and not stress it further. Patience is the key to bounce back from this issue.

Also Read: Best Soil for Growing Sweet Potatoes

Shock from transplant

Yellowing of leaves from a transplant shock is usually not a big deal and requires just a little time and patience to let the plant recover from the damage.

When you change the growing conditions of your plant suddenly, either from outdoors to indoors,or vice versa, it requires some time to adapt to the new environment. During its adaptation process, it cannot give sufficient attention to other functions of the plant, thereby resulting in some of the leaves turning yellow.

Plant disease

If you cannot spot any of the reasons from the aforementioned points, there are high chances that your zucchini plant has caught any of the following diseases, causing it to turn yellow. Here are three of the most common and dangerous plant diseases that can cause significant damage to your zucchini plant, yellow leaves being one of them:

The Cucumber Mosaic Virus is a common disease that is spread by a virus easily attracted to zucchinis. The symptoms of this disease can be easily picked up. The leaves will turn yellow, but in a splotchy way and the growth will be stunted for a long time, despite all the measures taken by you.

Fusarium Wilt is one of the most infamous diseases that has infected almost all the varieties of vegetable plants. It attacks the root system of the plant, thus weakening the entire plant functioning, and making the leaves yellow. An unfortunate ordeal about the fusarium wilt is that it is not affected by the cold weather and is almost always spread by the cucumber beetle.

If you are familiar with algae, then you would have also heard of the downy mildew. It looks remarkably similar to algae and gives its best shot in humid and cold weather. If the underside of your leaves display fungal pores and yellow spots, then it is highly likely that your plant is affected by the downy mildew. A good news with the downy mildew is that it is not always fatal and its effects drift away once the conditions normalize.

Insect infestation

We might not be aware of it but zucchini plants can sometimes become home to some of the most dangerous insects. They attract a host of insects, primarily because of their taste and odor. These insects do the job of eating up the leaves, thus making them wilted and yellow  brown.

Insects like aphids, squash bugs, spider mites, and squash mine borers suck the sap of the zucchini plants, thus draining all the important nutrients from it, and making it vulnerable to die.

How to treat yellow zucchini plant leaves?

In order to beat the nutritional deficiency of your zucchini plant, it is important to take into consideration a few remedial steps. These are as follows:

Treating the nutritional imbalances

Adding a well-rotted manure or compost is one of the most naturally proven ways to treat your plant for any nutritional deficiency. Adding a naturally prepared or commercially available compost will help your plant to fulfill its phosphorus and potassium needs. Adding compost allows your plant to absorb nutrients slowly, thereby making it a sustainable option to combat any deficiency.

While adding compost is an easy way out, making the pH levels of your soil balanced is another related way in which the nutritional problems can be treated. The ideal pH levels in which your plant thrives is 6.5 to 7 and adding a manure that is very well rotten can do wonders for your soil and the plant.

Watering your plants right

A common belief is that zucchini plants are intrinsically made of water so they might need more water to thrive. To the surprise of our readers, this is far from being true. Zucchini plants need only 2-3 cm of water once every week and not more than that. This is similar to the watering needs of most other house plants.

On the other end of the scale is underwatering. Not giving enough water to your plant results in withering and dying of plants, thus making them yellow. Do not overcome this situation by watering them immensely. Start in moderation and stay in moderation. Nothing more than 1 inch per week.

Further, many people water the plants from right above the leaves. This should be avoided if you are not looking for active invitations to fungal diseases and bacteria. Instead, drip irrigation is almost always supported. This method not only ensures that water reaches straight to your root system, but also helps in its wastage.

Provide adequate sunlight to your plant

One of the simplest ways to treat your plant for yellow leaves is by exposing it to 7 hours of direct sunlight every day. To do so, make sure that your plants are not rooted in a shady region of your garden. It can make things difficult for you at a later stage.

If you are growing your zucchini plant in a greenhouse or indoors, then it is important to install sufficient artificial lights to make up for the natural light deficiency. You can also make sure to pot your plants near a window, where the sunlight exposure is optimum.

Treating transplant shock

A transplant shock is generally considered a reflex of the plant towards new growing conditions and there is not really much that you can do about it.

However, you can certainly reduce the after effects by making sure to not transplant zucchinis until they are completely matured and hardened. Doing this can minimize the shock since it becomes less taxing for mature plants as compared to the amateurs.

Treating damage from insects and diseases

It is not easy to treat your plant if an insect infestation or disease has already made their way to it. But, you can try the most efficient methods like attracting beneficial insects that will eat up aphids and spider mites, thus reducing your problem.

Another way of getting rid of the disease damage is to spread pesticides on your plants after removing all the rotten and damaged parts of the plant. It is important to detach and discard them in a way that they do not come in contact with other plants and infect them.

Using floating row covers is a natural way to keep insects and diseases away from your zucchini plants. These fine mesh sheets repel undesirable insects and pests, thus keeping them at bay.


While it is true that zucchini plants are the easiest to grow, the fact they come with a set of problems of their own is also true. Their leaves turning yellow is just one of these problems that requires immediate attention and treatment solutions.

With the points mentioned in the preceding article, it should not be difficult for a newbie or a professional gardener to figure out what they need to do once their zucchini plant leaves turn yellow.

Additionally, you can also look up to the general steps that will help in taking care of the overall plant in the long-term. With the right amount of time, energy, and equipment, your zucchini plants can thrive for as long as you want.

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