Tomato leaves turning purple can be alarming for gardeners. However, in most cases, it is not a cause for concern and can be easily remedied. This comprehensive guide examines the various reasons why tomato leaves may turn purple, and provides useful tips to treat and prevent the problem.

What Causes Purple Tomato Leaves?

There are several potential causes of purple discoloration on tomato leaves:

Phosphorus Deficiency

A phosphorus deficiency is one of the most common causes of purple tomato leaves. Phosphorus is an essential nutrient that aids in important processes like photosynthesis and fruit development.

Without adequate phosphorus, tomato leaves can take on a purple or reddish-purple hue. Lower leaves typically show symptoms first. The edges and undersides of leaves often turn purple first, eventually spreading across the entire leaf surface.

Cold Temperatures

Exposure to cold temperatures can turn tomato leaves purple. Nighttime temperatures below 55°F (13°C) can trigger purpling of the leaves.

The pigments anthocyanins accumulate in the leaves in response to cold stress. This acts as a protective mechanism, but leaves will turn purple temporarily until temperatures warm up again.

Genetics

Some tomato cultivars are genetically predisposed to having purple foliage. Varieties like ‘Black Krim’ and ‘Cherokee Purple’ naturally develop intense dark purple leaves due to high anthocyanin content.

If leaf purpling is isolated to a single plant, there’s a chance it could be caused by genetics rather than nutrient issues.

Herbicide Damage

Certain herbicides like paraquat can cause tomato leaves to turn red, purple, or brown if the plants are exposed. Always take care to prevent herbicide drift during application.

Viral Diseases

Some viral tomato diseases produce purple leaf discoloration, such as tomato spotted wilt virus and tomato mosaic virus. However, there will be other viral symptoms present as well, like stunted growth and mottling.

Normal Older Foliage

As lower tomato leaves naturally age and senesce, they can take on a purple tinge before falling off completely. This is normal and not necessarily indicative of any nutrient deficiencies.

How to Fix and Prevent Purple Tomato Leaves

If your tomato leaves are turning purple, here are some tips to remedy and prevent the issue:

Test Soil and Apply Phosphorus

Since phosphorus deficiency is a leading cause of purple leaves, test your soil to determine if phosphorus is lacking. Optimal soil phosphorus levels for tomatoes are between 45-60 ppm.

If soil phosphorus is insufficient, work bone meal or rock phosphate into the soil. Compost and manure also contain phosphorus.

During the growing season, you can apply a phosphorus-containing fertilizer or foliar spray. This will provide a quick boost.

Check Soil pH

Soil pH profoundly impacts nutrient availability. Tomato plants absorb phosphorus best when the soil pH is between 6.0-7.5.

Use a soil test kit to check the pH. If it is too acidic or alkaline, apply amendments like lime or sulfur to achieve the ideal range.

Provide Adequate Calcium

Along with phosphorus, calcium deficiencies can also cause tomato leaf purpling. Ensure calcium levels are sufficient by blending organic matter like crushed eggshells into the soil.

Liquid calcium sprays applied to leaves can help. Choose calcium nitrate or calcium chloride formulas.

Increase Ambient Temperatures

If nighttime temperatures are too low, bring plants indoors or use row covers to protect them. Provide heat sources like cloches to maintain warm conditions.

Once temperatures increase, the purple foliar pigmentation should disappear.

Evaluate Varieties

If one tomato plant has purple leaves while others do not, it may be a varietal trait. Certain heirloom types like black tomatoes are prone to anthocyanin accumulation.

Choose alternative varieties if the purple foliage is undesirable. Or embrace it as characteristic of that particular cultivar.

Rule Out Herbicide Damage

Thoroughly wash leaves to remove any herbicide residue if exposure is suspected. Avoid spraying weed killers near tomato plants, and always shield them during application.

The damage cannot be reversed, but new foliage should return to normal once the plant is no longer exposed.

Monitor Other Symptoms

Carefully check plants for signs of viral infection, like leaf mottling and curling, growth abnormalities, and mosaic patterning. Have a plant lab test for viruses just to be safe.

Remove and destroy any infected plants right away. Sterilize tools after handling to prevent spread.

Remove Older Growth

Prune off heavily purpled lower leaves that are naturally senescing. This spurs new growth and allows the plant to focus energy elsewhere.

As long as purpling is limited to older foliage, it is likely just a product of normal aging.

When to Worry About Purple Tomato Leaves

Purple tomato leaves are not necessarily a major concern if caused by cold exposure, genetics, or aging. However, quick action is required if phosphorus deficiency or viral infection is suspected:

If soil tests confirm very low phosphorus levels, begin treatment right away to prevent stunted growth and reduced yields.
If purple discoloration appears across most of the plant at once, a virus may be spreading rapidly. Remove and destroy affected plants immediately.
Watch for other symptoms like wilting, spotting, yellowing leaves, or necrotic lesions which could indicate a more serious underlying problem.
Monitor purple lower leaves closely to see if the symptoms progress upward and intensify. This can signify a major nutrient deficiency.
Take note if flowering and fruit production seem reduced. This means the purpling foliage is impacting the plant’s overall vigor.

While temporary or varietal leaf purpling is no cause for alarm, significant color changes across multiple plants demands quick action to ward off nutrient deficiencies and viral culprits.

FAQs About Purple Tomato Leaves

Here are answers to some frequently asked questions about purple discoloration in tomato foliage:

Are Purple Tomato Leaves Always a Problem?

No, leaf purpling does not automatically indicate a problem. Some varieties naturally develop anthocyanins resulting in purple pigmentation. Exposure to cold and herbicide drift can also cause temporary purple coloration. Only when widespread among multiple plants is it a real cause for concern.

Can You Still Eat Tomatoes If the Leaves are Purple?

Yes, purple leaves do not affect the safety or flavor of the tomatoes themselves. As long as the fruits are ripening normally, they are still perfectly fine for consumption. Simply focus on diagnosing and resolving the underlying issue causing the foliar discoloration.

Do Purple Leaves Affect Tomato Production?

If caused by cold exposure or varietal traits, purple leaves should not significantly impact tomato yields. However, extensive purpling from phosphorus deficiency or viral infection can impair photosynthesis, reducing flower and fruit production. So it is important to identify and treat the cause.

Should Purple Tomato Leaves Be Removed?

Lightly pruning older lower leaves that naturally turn purple is fine, but wholesale defoliation is not necessary. As long as newer upper foliage looks healthy, the plant can still gain ample energy via photosynthesis through those leaves.

How Do You Fix Purple Tomato Leaves?

Test soil nutrient levels and pH. Correct any phosphorus deficiencies by applying bone meal or rock phosphate. Ensure optimal soil pH between 6.0-7.5 to maximize phosphorus availability. Rule out viral diseases. Increase temperatures if cold is suspected. Evaluate tomato varieties prone to anthocyanins.

What Tomato Plants Have Purple Leaves?

Black varieties like ‘Black Krim’, ‘Cherokee Purple’, and ‘Indigo Rose’ commonly exhibit purple foliage. Many other heirlooms like ‘Brandywine’ may also show a purple tinge on leaves. Siberian and other cold-tolerant cultivars adapt to cooler climates by accumulating protective anthocyanins.

Conclusion

While tomato leaves turning purple may look disturbing, it is not always a major threat to plant health. Cool weather exposure, genetics, aging, and phosphorus deficiencies are common culprits. To ensure optimal tomato growth, maintain adequate soil fertility, ideal pH, sufficient phosphorus levels, and protect plants from temperature fluctuations. Monitor for viral diseases and weed killers as well. With attention to proper culture and nutrition, purple foliage can be prevented and treated if it does occur.

Why Are My Tomato Leaves Turning Purple? – FAQs

What causes purple or red leaves on tomato plants?

The most common causes of purple tomato leaves are phosphorus deficiency, cold temperatures, genetics, herbicide damage, viral diseases, and normal aging of lower leaves.

How can I fix purple leaves on my tomato plants?

Test and amend the soil pH to between 6.0-7.5. Ensure sufficient levels of phosphorus and calcium. Increase temperatures if cold is the issue. Rule out herbicide exposure and viral infections. Prune older purple foliage.

When should I be concerned about purple leaves on tomatoes?

Monitor for spreading purple discoloration across multiple plants, as this indicates a phosphorus deficiency or viral disease requiring quick action. Also watch for other symptoms like wilting, spots, and poor flowering/fruiting.

Can I still eat tomato fruits if the leaves are purple?

Yes, the tomatoes themselves are still perfectly safe to eat. The purple foliage does not affect the flavor or quality of the fruits.

Should I remove tomato leaves that turn purple?

Light pruning of older lower leaves is fine, but extensive defoliation is unnecessary. As long as upper new growth looks healthy, the plant can still photosynthesize through those leaves.

Why do some tomato varieties have genetically purple foliage?

Purple pigmentation in certain tomato cultivars results from a high accumulation of anthocyanin antioxidants. This acts as a protective mechanism against stresses like cold temperatures and sun exposure.

Can cold temperatures turn my tomato leaves purple temporarily?

Yes, chilly weather below 55°F (13°C) triggers anthocyanin production in the leaves as an adaptive response. Foliage will return to normal once warmer conditions prevail again.

How can I prevent purple tomato leaves from appearing?

Test soil fertility and pH annually. Apply phosphorus fertilizer and calcium amendments if needed. Use row covers and heat sources to maintain ideal temperatures, especially at night. Select tomato varieties less prone to purple pigmentation.

What are the optimal soil phosphorus levels for preventing purple tomatoes leaves?

Tomato plants grow best with soil phosphorus levels between 45-60 ppm. Applying compost or bone meal can help supply phosphorus if deficient.

Should I have my purple tomatoes tested for viruses just to be safe?

Yes, submitting samples to a plant diagnostic lab can definitively rule out viral diseases. Catching them early allows for removal of infected plants before they spread.

Why Are My Tomato Leaves Turning Purple?

Introduction

Purple or reddish discoloration in tomato foliage can raise concerns for gardeners. However, leaf purpling is not always detrimental, and may be caused by genetics, weather, or normal aging. This article examines the common reasons behind purple tomato leaves, when action is required, and how to remedy and prevent the issue through proper care.

Reasons for Purple Tomato Leaves

Many factors can potentially lead to purple pigmentation showing up in tomato leaves:

Soil Nutrient Deficiencies

Phosphorus – Insufficient levels of phosphorus typically cause the most common cases of purple leaves. This vital nutrient aids photosynthesis and fruit formation. Deficiency causes reddish-purple discoloration first seen on oldest leaves.
Calcium – Along with phosphorus deficiency, inadequate calcium can induce tomato leaf purpling. This mineral supports cell structure and growth.

Environmental Stresses

Cold Temperatures – Chilly weather below 55°F (13°C) triggers accumulation of purple anthocyanin pigments in leaves. This acts as protection against cold stress until warmth returns.
Herbicide Damage – Drift from nearby applications of paraquat or other weed killers can make tomato foliage turn purple or brown.

Diseases

Viral Infections – Tomato spotted wilt, mosaic virus and other pathogens may produce leaf purpling along with other symptoms like mottling, stunting, and lesions.

Genetics

Anthocyanins – Some heirloom varieties have naturally high levels of anthocyanins resulting in dark purple foliage as a varietal trait. Examples are Black Krim and Cherokee Purple types.

Normal Senescence

Lower Leaf Aging – Lower mature leaves often take on a purple hue before dropping off as part of the normal aging process. This is not problematic in itself.

Diagnosis and Solutions

If tomato leaf purpling occurs, here are tips to identify the cause and restore healthy foliage:

Check soil nutrients – Test levels of phosphorus and calcium and amend if deficient. Ideal pH is 6.0-7.5.
Increase temperatures – Protect plants from cold under row covers or cloches if purple occurs during cool weather.
Rule out herbicides – Wash off any chemical residue on leaves and prevent future drift exposure.
Monitor for viruses – Watch for multiple symptoms. Have plants tested at a diagnostic lab for confirmation.
Prune old leaves – Remove heavily purpled lower leaves to focus growth on new foliage.
Select varieties – Avoid types like black tomatoes prone to anthocyanin pigments if undesirable.

When to Worry

Purple tomato foliage due to cold, aging, or genetics is not concerning. However prompt action is required if:

Multiple plants exhibit spreading purple discoloration, signaling phosphorus deficiency or viruses.
Leaf purpling is accompanied by wilting, spots, poor flowering and other abnormalities.
Overall tomato vigor appears weakened, with stunted plants and reduced yield.

Preventing Purple Leaves

Follow good cultural practices to avoid purple tomatoes leaves:

Test and amend soil annually to maintain optimal pH and nutrient levels.
Add phosphorus fertilizer or bone meal if deficiency is suspected.
Ensure sufficient calcium levels.
Use row covers, cloches, or other protection to prevent cold injury.
Select resistant varieties less prone to developing leaf purpling.

Conclusion

While purple tomato foliage may look troubling, it is not always detrimental. Cool weather, plant genetics, and lower leaf senescence commonly induce temporary or varietal leaf purpling without major impact on plant health or fruit productivity. However, phosphorus deficiency and viral diseases can lead to lasting damage, so immediate action is required if tomato leaves turn purple across multiple plants or do not recover. With vigilance and attentive care focused on soil fertility, temperatures, and variety selection, gardeners can prevent or resolve purple discoloration in tomato leaves.

Why Are My Tomato Leaves Turning Purple? – FAQs

What causes purple or red leaves on tomato plants?

The most common causes of purple tomato leaves are phosphorus deficiency, cold temperatures, genetics, herbicide damage, viral diseases, and normal aging of lower leaves.

How can I fix purple leaves on my tomato plants?

When should I be concerned about purple leaves on tomatoes?

Monitor for spreading purple discoloration across multiple plants, as this indicates a phosphorus deficiency or viral disease requiring quick action. Also watch for wilting, spots, poor flowering/fruiting.

Can I still eat tomato fruits if the leaves are purple?

Yes, the tomatoes themselves are still perfectly safe to eat. The purple foliage does not affect flavor or quality of the fruits.

Should I remove tomato leaves that turn purple?

Light pruning of older lower leaves is fine, but extensive defoliation is unnecessary. As long as upper new growth looks healthy, the plant can still photosynthesize.

Why do some tomato varieties have genetically purple foliage?

Purple pigmentation in certain tomato cultivars results from a high accumulation of anthocyanin antioxidants. This acts as protection against stresses like cold and sun exposure.

Can cold temperatures turn my tomato leaves purple temporarily?

Yes, chilly weather below 55°F (13°C) triggers anthocyanin production in the leaves as an adaptive response. Foliage will return to normal once warmer conditions prevail again.

How can I prevent purple tomato leaves from appearing?

What are the optimal soil phosphorus levels for preventing purple tomatoes leaves?

Tomato plants grow best with soil phosphorus levels between 45-60 ppm. Applying compost or bone meal can help supply phosphorus if deficient.

Should I have my purple tomatoes tested for viruses just to be safe?

Yes, submitting samples to a plant diagnostic lab can definitively rule out viral diseases. Catching them early allows for removal of infected plants before they spread.