Do you spot curling leaves on your tomato plants, and you don’t know why it’s happening?
Tomato leaves curl because the plant is in distress from watering, nutrient, or disease issues. Luckily, there are ways to solve and correct the problem and watch the plant go on to produce a healthy harvest.
However, learning how to spot why your tomato leaves are curling takes practice and a keen eye.
I hope the information below helps you catch tomato leaf curling issues in time to keep your plants alive and your garden free of disease or pests so you can enjoy juicy, sweet tomatoes fresh from your garden season after season!
What Causes Tomato Leaves To Curl?
These factors are often the cause of the curling of tomato leaves:
- Uneven plant development
- Improper watering
- Diseases or Pests
- Weather
- Fertilization or herbicide issues
Let’s dig into each reason and highlight the signs that can help you pinpoint why your tomato leaves are curling, so you know how to treat it.
Growth Imbalance
Tomato plants that grow quickly often have dense upper foliage but lack the root system to support it and begin to falter.
This growth imbalance is a prevalent cause of leaf curl. Any root damage, such as during transplanting or weeding, can stress the plant’s upper part, making leaves curl.
When the root system is weak, the leaves will remain green, but the lower leaves will curl upward on the outer edges while the leaf’s inner part will curl downward.
As the condition worsens, the tomato plant’s upper leaves will begin to curl as well.
Too Little or Too Much Water
Like any plant, too little water will cause distress, which you’ll see in leaves that curl up on the edges, begin to look dry, and the plant begins to droop.
Roots of thirsty tomato plants must maintain a consistent moisture level in the soil for continual water uptake into the plant. When plants go without water for even a short time, leaves will begin to curl up.
Overwatering can lead tomato leaves to curl downward, which indicates the plant cannot take in any more moisture.
Downward curling tomato leaves are a sign of possible root rot.
Diseases or Pests That Cause Curling
A common disease that attacks tomato plants is the Yellow Leaf Curl Virus. As the name suggests, the virus will cause curling of the tomato leaves and turn them yellow. Another sign is that flowers never form or develop into a fruit.
In arid areas of the US, Curly Top Disease causes tomato leaves to not only curl up but also twist, making it easy to identify.
Bacterial Wilt causes tomato leaves to curl and slightly wilt during the hottest part of the day, but the leaves often recover as the temperatures cool. As the disease progresses, the leaves remain green, but more will curl and wilt on the plant.
Shade-loving Broad Mites (Polyphagotarsonemus latus) are a tiny pest that leaves behind toxins as they feed on tomato flowers and small leaves. As a result, the leaves will curl and bend in all directions and take on a reddish-brown tone on the shady underside where they like to live.
Weather Conditions
Tomato plants react very fast to weather conditions, especially high heat, high winds, dusty wind, and low humidity.
These weather issues will cause tomatoes to curl up their leaves to protect the plant as part of its natural defense mechanism. The more the plant feels in danger, the tighter the leaves will curl up.
Problems that affect the body of the tomato plant cause this physiological leaf curl, which is a way for the plant to stop any more water loss from adverse weather conditions.
Herbicide Exposure
Tomato plants are extremely sensitive to certain chemicals found in herbicides, fungicides, and insecticides with a hormone base.
Even if you follow organic gardening practices, your tomato plants can still have exposure to herbicide drift from farms nearby.
The drift of chemicals can reach up to a mile in low wind conditions, with stronger winds pushing them much further, giving them a chance to land in your garden.
Store-bought compost and mulch can carry traces of these chemicals. Garden plots can retain residue from herbicidal treatments for up to 18 months.
The impact on your tomato plants will occur in the form of leaves rolling downward at the tips and sides and slightly twisting. Splitting stems is another sign that often happens along with the leaf curl.
How To Treat Tomato Leaf Curl
Treating tomato leaf curl will vary depending upon how severe the damage is to the plant.
In many instances, proper watering and protection from the elements can help tomato plants regain health and continue to produce fruit.
Water Correctly
Tomato curl happens when plants don’t receive deep waterings.
Short watering sessions every day or two encourage plants to grow a shallow and weak root system that has to work harder to hydrate the foliage and prevent the leaves from curling.
Begin watering the plants deeply every few days, which will stimulate roots to grow deeper while also providing enough consistent moisture to the leaves. Wait until the top two inches of the soil is dry, which is easy to do by using a moisture meter.
Watch Tomato Plant Spacing
Tomato plants growing too close together will also stunt proper root development and cause an even worse leaf curling issue as they fight with each other for water.
Keep individual plants 24-36 inches apart for ideal growth that will result in a better tomato harvest.
Watch Your Use Of Fertilizer
For tomato plants, use a fertilizer low in nitrogen.
Too much nitrogen will cause the foliage growth to explode, stressing the root system and causing leaf curl from lack of moisture.
Weather Protection Tips
Tomato plants are sensitive to the effects of wind, especially in dry, dusty regions. As the air passes over the leaves, it pulls moisture from the plant, causing leaves to curl.
If you see tomato plant leaves curling, and you know you’re watering correctly, and there’s no sign of pests or disease, add a windbreak around your crop.
For a quick and inexpensive fix, you can use garden stakes and a barrier cloth to reduce harsh winds and give your tomato plants a chance to recover.
For future planting, consider placing tomatoes in a greenhouse or in your yard where there are already windbreaks in place, such as near:
- Fences
- Walls
- Hedges
- Buildings
Tackle Disease Issues Quickly
When tomato leaf curl is from pests or disease, the best way to treat it is to remove the plant immediately from your garden before it spreads to other plants.
For safer results, follow this how-to on removing tomato plants suffering from Tomato Leaf Curl Virus from your garden.
Trying to treat the tomato plant with herbicides or pesticides is usually a waste of time and money, so pull the plant and focus your energy on the rest of the crop.
Using topical treatments may save the plant, but rarely will it develop fully and produce an average amount of flowers and fruit.
Protect Tomatoes Against Herbicide Damage
If you rule out all other possible causes of curling tomato leaves, your plant is most likely suffering from the effects of a herbicide.
Never use herbicides directly in your vegetable garden, as even a small amount can lower tomato crop yield.
Trying to combat herbicides blowing in the wind can be challenging. Even glyphosate herbicides commonly used in weed and feed treatments on lawns can damage your tomato plants.
You can grow tomatoes in a greenhouse, which will help deter windborne herbicides from getting on the plants. You can also use the windbreak suggestions above to lower herbicide contamination.
If you see curling leaves from herbicide exposure in young plants, it’s wise to remove them from the garden as they will produce a low yield.
Older plants with flowers or small fruits should survive this exposure, even if the leaves don’t look ideal during the rest of the growing season.
If you use herbicides in certain areas of your garden, always burn any plant remains at the end of the growth cycle. Burning of the ground and plants will help herbicide residue decompose quicker.
