Leaves curling is one of the most commonly seen problems in plants and Zinnias are no exception.
Although stunning flowers are the main reason for growing zinnias, healthy foliage also has a role in the overall attractiveness of the plant.
The most prevalent cause for zinnia leaves curling is pest attack and inadequate watering. If these two issues are not present, then lack of proper light, overfertilization, temperature stress, or lack of moisture in the air could be the reason.
Now, let’s go through each of these causes in detail with possible solutions so that you know what to do to reverse the curling as fast as possible.
1. Pest diseases
Since zinnia plants are mostly grown outdoors, the number one reason for zinnia leaves curling is pest diseases.
The commonly found pest is the Leaf Curl Virus which is very rapid in terms of action. Within a few days of exposure, the entire plant may get affected. The other pests include aphids, mealybugs, thrips, and whiteflies.
All the vital nutrients required for the healthy growth of leaves are sucked out of the plant sap by these flies and insects. If the infection is severe, the leaves may lose their ability to receive nutrients from the stem to the leaves, causing them to droop and curl.
These pests typically hide beneath the leaves, making it difficult to locate them. It is advised to buy a portable LED lamp so you can occasionally check the plants. Considering how tiny spider mites and other similar insects are, it might be wiser to use a magnifying lens when inspecting your zinnia plants.
Different types and concentrations of insecticides are required for various pests. To begin with, though, you can clean the harmed leaves and stem with diluted neem oil, insecticidal washing solution, or peppermint oil.
When an infection is particularly bad, you should look for insecticides that are manufactured specifically to resist such pests. These are highly developed chemical compounds which should be used only if necessary.
2. Too much or too little water
If you don’t see any pests, then the curling of zinnia leaves is probably due to a fault in its care routine or the environment it is in.
Among the care and environment issues, lack of proper watering is the number one reason for zinnia leaves curling. Watering issues include both underwatering and overwatering.
The biological element known as turgor, which is in charge of making the living plant tissue rigid, will be lost if your zinnia plant is getting very little water. Unless the tissue in the leaves is stiff, it will begin to curl.
On the other hand, if your zinnia plant is getting too much water, the roots of the plant start to rot and the leaves will curl.
The best way to fix the overwatering or underwatering problems is by fixing a proper watering schedule based on the external climate conditions. Always check that the top two inches of soil are totally dry before watering.
Additionally, it is strongly advised that you keep a record detailing your zinnia plant’s watering schedule and keep it in a visible location to ensure that you never forget.
3. Lack of proper light
It is not a surprise to see a lack of proper light among the top reasons for zinnia leaves curling. Along with water and soil, light is essential for plant functions.
The photosynthetic cells of the leaves can be harmed by too much strong light, which causes the leaves to curl and finally dry.
On the other hand, too little light prevents plant cells from doing photosynthesis, which results in dull-looking leaves and the entire plant.
It is not difficult to determine whether the curling leaves on your zinnia are caused by temporary stress or not. All you have to do is simply look at which way the leaves curl.
Your zinnia plant is not receiving enough light if the curl is pointing directly at the source of illumination. On the other hand, if they start to curl away from the light source, it is too bright.
It is very common among beginner gardeners to over feed their plants in an effort to increase the nutrient content in the soil so that the plant will grow faster and bloom quicker.
When your zinnia plants get too much fertilizer, the excessive chemical buildup in the soil suffocates the roots and as a result, some roots will rot.
Once a major chunk of roots is rotten, the healthy roots cannot solely support the plant’s requirements. When the requirements of the whole plant are not met, leaves start to curl, turn yellow or droop depending on the severity of the issue.
To remedy this, stop fertilizing for a while and replace the soil around your zinnia plant. You may either mix your own soil or just get it from a nearby gardening supply store. The new soil can then be fertilized with a modest mixture of nitrogen-rich fertilizer once a month during the growing season.
5. Lack of nutrients
We just saw that overfertilization can cause zinnia leaves to curl, but according to many reports, under-fertilization can also trigger the same issue.
Instead of under-fertilization, the correct phrase to use is nutrient deficiency. Zinnia leaves curling is mostly due to the deficiency of nitrogen.
Nitrogen deficiency always affects the lowest or oldest leaves first before new leaves. It is because the plant diverts nutrients from the existing leaves when the new leaves don’t receive enough from the soil to support their growth.
The best way to prevent nitrogen deficiency is to provide a continuous supply of nitrogen to your zinnia plant by having a proper fertilizing schedule.
6. Heat & humidity stress
According to The University Of Maryland Extension, even when there is sufficient soil moisture, heat and humidity stress can cause flowering plants’ leaves to curl.
When external temperature is very high, zinnia roots are not capable of supplying the required water to the leaves and as a result, the leaves curl and droop. This happens because the zinnia roots are unable to keep up with the rate at which moisture is evaporating from the zinnia leaves.
The logic behind humidity stress is also similar. When the humidity is too low, the moisture content from the leaves is sucked by the air quickly making the leaves curl temporarily.
It is not easy to fix both temperature and humidity stress. The maximum you can do is to move the plant to a better spot where the temperature is a little less.
7. Natural curling
The curling of zinnia leaves is not always caused by a fault in the care routine or its growing environment.
Sometimes, it can be simply natural.
It’s normal for the older leaves of your zinnia plants to occasionally curl, and turn yellow. During the growing season, your plant will be putting out a lot of new growth. In such instances, the plant will be spending its focus and energy on new growth instead of old mature leaves.
It is recommended to prune the curly leaves on your zinnia plant with a pair of gardening shears. When you get rid of these leaves, the plant can easily focus on new growth. As a result, it will look healthier and more vibrant.
Zinnia Leaves Curling – Frequently Asked Questions (FAQs)
When you notice curly leaves on your zinnia plants, it’s very natural to have many doubts. In this section, we will be answering some of the most commonly asked questions on internet forums about zinnia leaves curling so that you don’t have to search for them separately.
Can zinnia leaves recover from curling?
Unlike yellowing or browning, the curling of zinnia leaves can be reverted easily with correct measures taken on time.
Why are my zinnia leaves curling only upwards?
When your zinnia plant does not get enough light, its leaves start to curl towards the light source to attract more light. In outdoor conditions, the light source will be the sun, as a result, the leaves curl upwards.
Why are my zinnia leaves curling only downwards?
Your zinnia plant is most certainly receiving too much light if all of its leaves are curling only downwards. In general, plant leaves begin to curl downwards away from the light source when the plant is receiving excessive light.
Should you cut off curly zinnia leaves?
Since curly zinnia leaves can be recovered, there is no need to cut them off. However, if a lot of leaves are curly and are making the plant look dull, then you can prune some of the leaves to make the plant attractive while other leaves recover.
Zinnia leaves curling is not a serious problem, in fact, it’s just a small clue that something is wrong with the growing condition of your plant.
Sit back and analyze what have you done wrong. Is that overwatering or overfertilization? Once you can pinpoint the real issue, you can easily solve it and prevent it from happening in the future.
To back up the information we provide in our articles, the Plantials team only uses high-quality sources published in peer-reviewed university or scientific research journals.
- Effect Of Growth Parameter & Quality Of Zinnia Bedding Plants, International Journal Of Horticultural Science & Technology.
- Effects Of Water Stress During Growth In Zinnia Elegans, International Society Of Horticulture Science.
- How To Grow Zinnia Plants, Flower Breeding & Genetics Book.
- Cut Flower Zinnia Production In Greenhouse, University Of Florida.
- Heat Stress Symptoms On Flowering Plants, University Of Maryland Extension.
- Pests In The Urban Landscape, UC Statewide Integrated Pest Management Program.