Growing your own zucchini can be a rewarding and economical experience.
But like any garden endeavour, it can come with its fair share of challenges.
One of the common issues gardeners face is yellowing zucchini leaves.
If your zucchini plants are turning yellow, don’t panic! It usually is a sign of a treatable problem.
Possible Causes of Yellowing Zucchini Leaves
Yellowing leaves can be caused by various factors, some more serious than others. Here are a few possibilities:
Nutrient Deficiencies
Like any other plant in your garden, zucchini plants require a balanced supply of nutrients to thrive.
Zucchini leaves may turn yellow if they lack essential nutrients, particularly nitrogen, iron, or magnesium.
Overwatering or Poor Drainage
Zucchini plants love well-drained soil.
Overwatering or poor drainage can lead to waterlogged roots and yellowing leaves.
Natural Aging Process
As zucchini plants mature, it’s normal for older leaves lower on the plant to turn yellow and eventually drop off.
Common Zucchini Plant Diseases
Several pests and diseases can cause zucchini leaves to turn yellow. Here are a few, along with potential treatments:
Aphids
Aphids are small, sap-sucking insects that can cause zucchini leaves to turn yellow and curl.
You might see them on the undersides of leaves.
To control aphids, spray the leaves with a strong jet of water to knock them off, or use an insecticidal soap or neem oil.
Spider Mites
These tiny mites are hard to see with the naked eye but can cause significant damage.
Spider mite-infected leaves might look speckled or mottled before turning yellow.
They thrive in dry conditions, so increasing humidity can help. In severe cases, use an insecticidal soap or miticide.
Squash Bugs
Squash bugs can cause yellow spots that eventually turn brown, and you might also see wilting.
Handpick these bugs and their eggs off plants, or use an insecticidal soap.
Powdery Mildew
This fungal disease causes a white, powdery substance on the leaves, which can eventually turn yellow and brown.
Ensure good air circulation around your plants, and avoid watering from overhead to keep leaves dry. Fungicides can help in severe cases.
Bacterial Wilt
This disease is spread by cucumber beetles, causing plants to wilt and leaves to turn yellow.
Unfortunately, once a plant is infected, it often can’t be saved.
Remove and dispose of infected plants, and control cucumber beetles with insecticides or floating row covers.
Verticillium Wilt
This soil-borne fungus causes older leaves to yellow and wilt.
If you suspect this disease, you may need to remove the infected plant and avoid planting in the same area for several years.
How to Fix Yellowing Zucchini Leaves
You can begin treating your plants once you’ve identified the possible cause.
Here are some home remedies to fix yellowing leaves on zucchini plants:
Nutrient Deficiencies
Improve the nutrient content of your soil by adding organic compost or a balanced vegetable fertiliser.
- For nitrogen deficiency, consider adding a nitrogen-rich organic fertiliser or composted manure.
- Consider using a foliar spray with the deficient nutrient for iron or magnesium deficiencies.
Overwatering or Poor Drainage
Adjust your watering schedule based on the weather and the plant’s needs.
Zucchini plants typically require an inch of water per week.
Your zucchini plant’s watering needs may need to be increased during hot, dry weather and decreased during periods of heavy rainfall.
If drainage is an issue, consider amending your soil with organic matter to improve its structure and water-holding capacity.
Natural Aging Process
If only the older leaves are yellowing and the plant is otherwise healthy, you likely don’t need to do anything.
Companion Planting for A Healthy Zucchini Plant
Companion planting can significantly benefit your zucchini plants.
Good Companions for Zucchinis
Beans
Beans are excellent companions for zucchinis as they help fix nitrogen in the soil.
However, avoid planting too close as both plants need space to spread.
Corn
Corn and zucchinis work well together in the classic “Three Sisters” companion planting method (with beans as the third sister).
The corn provides a natural trellis for the beans, and the zucchini provides ground cover, reducing weed growth and maintaining soil moisture.
Nasturtiums
Bright nasturtium flowers add beauty to your garden and help repel several pests that can bother zucchini, including aphids and squash bugs.
Marigolds
Like nasturtiums, marigolds can help keep pests away from zucchinis.
They’re particularly known for deterring nematodes, tiny soil-dwelling pests.
Radishes
Radishes planted around zucchinis can deter squash vine borers, a pest that can devastate zucchini plants.
Peas
Like beans, peas help enrich the soil with nitrogen, aiding zucchini growth.
Plants to Avoid Near Zucchinis
Potatoes
Potatoes and zucchinis compete for nutrients and space.
They’re also both susceptible to blight, so keeping them apart helps prevent the spread of this disease.
Pumpkins
Zucchinis and pumpkins can easily cross-pollinate because they are members of the same plant family.
This can lead to less-than-desirable fruits. They also compete for space and nutrients.
Cucumbers
Cucumber plants attract the same pests, so keeping them apart is a good idea to prevent infestations.
In addition to using companion plants, remember to rotate your crops every year to prevent the buildup of diseases and pests in the soil.
When to Consult a Professional
While most causes of yellow zucchini leaves can be resolved with home remedies, it might be necessary to seek the advice of a professional gardener.
Persistent Problems
If you’ve tried the above remedies and your plants are still struggling, it may be time to call in a pro.
They have the knowledge and resources to diagnose and treat more complex issues.
Significant Pests or Disease Outbreaks
If your zucchini plants are experiencing a significant pest infestation or disease outbreak that you cannot control, a gardening professional can provide the appropriate treatment and advice.
Overall Garden Health
When your zucchini leaves turn yellow, it can indicate deeper issues with your garden, such as poor soil quality or improper pH levels.
A gardening expert can conduct a thorough analysis of your garden and provide tailored solutions.
FAQs About Yellow Zucchini Leaves
What do overwatered zucchini plants look like?
Overwatered zucchini plants often have yellowing leaves that may look wilted or lifeless.
Despite this wilting appearance, the leaves often feel soft and bloated due to excess water.
Zucchini plant roots of overwatered plants may become waterlogged, leading to root rot, further deteriorating the plant’s health.
Should you remove yellow leaves from zucchini plants?
If the yellowing of leaves is due to disease, pest infestation or nutrient deficiency, you should remove them.
This can prevent the spread of disease and help the zucchini plant direct its energy towards healthier leaves.
However, make sure to sanitise your tools before and after to prevent any spread of disease.
If the yellowing is just due to natural ageing, removing them is unnecessary as the zucchini leaves will drop on their own.
Why does my zucchini keep turning yellow?
If the fruit itself is turning yellow instead of the usual green, it could be due to a lack of pollination.
Zucchini plants have separate male and female flowers, and if the female flower is unpollinated, the fruit will start to grow but will turn yellow and eventually wither.
Improving zucchini pollination by attracting pollinators or hand-pollinating can help.
In some cases, specific varieties of zucchini are supposed to be yellow.
So make sure you know what variety you’re growing!
Why does my zucchini plant have yellow flowers?
Zucchini plants naturally produce yellow flowers.
They have separate male and female flowers on the same plant.
Male zucchini flowers usually appear first and are on longer, thinner stems.
The female flowers have a small swelling (a tiny, immature zucchini) at the base and are usually on shorter, thicker stems.
Both types of flowers are bright yellow and are perfectly normal and necessary for the plant to produce fruit.
