Cucumber Leaves Turning Yellow- Causes & Solutions

Cucumber growing
Cucumber leaves may turn yellow due to overwatering, inadequate lighting, nutrient deficiency and so on.

Cucumbers make one of the quickest growing crops as they are ready for harvest within 50 to 70 days of sowing seeds.

The lush green leaves and sizeable yields indicate that your Cucumbers are thriving, but keep an eye out for suspicious yellowing leaves.

Generally, premature yellow Cucumber leaves may indicate inadequate lighting, overwatering, iron deficiency, and disease infection. To fix yellow leaves, provide ample direct sunlight and warm temperature, correct watering schedule, feed iron-rich fertilizer, and keep an eye out for pests and diseases.

Yellow Cucumber Leaves
Cucumber leaves will turn yellow due to environmental change and moisture stress.

However, you can successfully revert yellowing leaves if you catch the symptoms early and apply immediate treatment.

Read on to find out what may cause yellowing Cucumber leaves and ways to treat them on time.

Is it Normal for Cucumber Leaves to Turn Yellow?

“Why are my cucumber leaves turning yellow and dying?” -if this question haunts you, you should know that seeing yellow leaves is quite normal.

The Cucumber leaves turning yellow with brown spots indicate that they are decaying, which happens once they mature, especially the bottom leaves.

Cucumber leaves turning yellow
It is normal for Cucumber leaves to turn yellow, as bottom yellowing leaves may indicate plant aging.

It is prevalent at the end of the growing season when the Cucumber plant demands the pruning of decayed foliage to conserve energy for long winter hibernation.

However, any yellowing seen on the leaves early in the growing season or anywhere between indicates a severe problem. In fact, it may not be expected at all.

The primary reasons why Cucumber leaves would prematurely turn yellow is due to deficiencies in the soil and light, deadly horticultural diseases and pests, and overly moist conditions.

Cucumber plants are warmth-loving crops that thrive in full sunlight with optimal moisture and iron-rich substrate.

Therefore, expect to find yellowing foliage and poor quality yields in your compromised Cucumber plants.

Why are my Cucumber Leaves Turning Yellow? (Causes & Solutions)

Cucumbers are friendly plant that requires enough warmth, fertile soil, and sunlight to thrive; you do not need to pay special attention or provide royal care!

However, things rarely turn out as you expect; hence, you have the problem of yellowing leaves on hand.

Here is the list of primary reasons that may cause yellowing cucumber leaves and their solutions.

1. Inadequate Lighting

The Cucumber is a fruit-bearing plant that requires full sunlight throughout the growing season to maintain healthy root and stem growth.

In fact, the vining Cucumbers’ roots can reach 36 to 48 inches deep, and stems can grow as tall as the trellis with bushier foliage and fruit growth.

These plants love the warmth and light, requiring at least 6 to 8 hours of sunlight daily.

Here is a quick overview of the importance of lighting duration for plants;

Sunlight DurationOutcome
<4 HoursPoor quality yields
4-5 HoursStalled growth with tiny fruiting
6-7 HoursEnsures healthy plant with good yields
8-10 HoursEnsures best growth with rich yields
>10 HoursLeads to transpiration and leaf loss

Therefore, robbing them of precious sunlight will prevent healthy fruit growth and green leaves.

Moreover, lack of chlorophyll is the primary culprit for yellowing Cucumber leaves.

However, leaving them high and dry in the scorching sun will burn the foliage with a visible hollow surface.

Solutions

  • Plant the Cucumber rows in the south-facing garden so that each sapling can get ample sunlight throughout the day.
  • Avoid planting them close to trees and tall plants, which may provide shade throughout the day.
  • Build an arbor or pergola around the Cucumber rows to ensure they get afternoon shade and prevent burn.
  • Plant them in mid-spring or early summer when the sunlight is at the fullest. The University of Maryland suggests providing 8 to 10 hours of sunlight per day.
  • Consider moving your Cucumber indoors under artificial LED light for at least 12 hours each day in areas with less sunlight.

2. Overwatering the Plant

Cucumber plants love regular watering but hate sitting in a pool of water.

They need consistent watering of about 1 to 2 inches a week and nothing more. Moreover, the soil should be well-drained to exert excess water into the ground.

Therefore, overwatering Cucumber plants may lead to moisture stress, which is indicated by yellowing foliage.

The overwatered Cucumber plant will choke in as the roots are deprived of oxygen and nutrients.

The leaves will be robbed of nutrients and oxygen required for food production, leading to a yellowing and wilting appearance.

Both inconsistent and overwatering can lead to choked roots and sometimes root rot due to excess moisture.

Cucumber plant in a pot
Overwatered Cucumber plants may display yellowing foliage.

Solutions

  • Start with following a watering schedule for your garden-grown Cucumber plant.
  • Introduce drip irrigation where drops of water trickle on the soil consistently to control water intake.

As a general rule, you will need to water your Cucumber plants every 2 to 3 days during the spring season and 4 to 6 times each week during the summer season.

  • Consider growing Cucumber in a raised bed with well-drained soil to avoid poor irrigation.
  • Use a soil-moisture meter every week or before watering (Anything above 6 indicates an overwatered plant).
  • Cut watering in monsoon when the rainfall is prevalent or add a canopy to prevent rainwater from seeping into the soil.

3. Nutrient Deficiency

Cucumber plants deprived of nutrients, especially iron or iron sulfate, will exhibit sickly-looking structures with yellowing leaves.

Iron deficiency may lead to young plants developing interveinal Chlorosis, where the foliage appears yellow with deep green veins.

You can tell your plant suffers from nutrient deficiency when the older leaves stay green, but the young leaves change color.

Similarly, nitrogen, calcium, and magnesium deficiency due to soil salinity, waterlogged soil, and a high supply of potassium or ammonium from over-fertilization may also cause yellowing leaves.

Yellow and stunted growth of Cucumber
Nutrient deficiency may cause yellow foliage and stunted growth of Cucumber.

The young leaves may look distorted and cup downwards or produce a light tan burn inside the yellow area.

Here is how each nutrient plays a role in plants growth;

NutrientsSpecification
NitrogenNitrogen is essential for the vegetative growth of the plant and also helps in the production of protein and enzymes.
PhosphorusPhosphorous assists in photosynthesis and is essential for healthy growth.
PotassiumPotassium is essential for the movement of water, nutrients, and carbohydrates in plant tissue.
Iron, Nickel, Copper-Boron, Zinc, Chlorine, and ManganeseIt helps in the bushier and healthier growth.
Assists in root development and encouraging soil microorganisms.
Calcium, Sulphur, and MagnesiumTrace elements help to maintain the plant’s immune system.
It boosts metabolism and helps retain nutrients.

Solutions

  • Introduce appropriate fertilizer for Cucumber plants such as Miracle-Gro 2000422 Plant Food or Jobe’s 09026NA Plant Food Vegetables & Tomato.
  • Use a fertilizer with a ratio of 5-10-10 to ensure optimal nitrogen intake without overfeeding.
  • Spray liquid iron on the foliage or use chelated iron in granular form on iron deficient plants.
  • Avoid using ammonium-based fertilizer such as chemical plant food.
  • Spray soluble magnesium nitrate or Epsom salt to the magnesium deficient plant once or twice until the condition improves.
  • You can also use coffee grounds or organic compost to avoid nitrogen deficiency in plants.

Avoid using excessive nitrogen-based fertilizers as it may result in excessive foliage and no fruits at all.

4. Poor Soil Condition

Cucumber plants thrive in loamy, well-draining soil as it promotes root development and controls water uptake.

Compact soil will deprive roots of oxygen and encourage bacterial and fungal growth leading to the sickly-looking plant and yellowing foliage.

In an ideal soil condition, the plant will grow 36 to 48 inches of roots; therefore, you should use the correct potting mix for garden and indoor-grown Cucumber plants.

Cucumber seedling growing in nutrient rich soil
The Cucumber plant thrives in a nutrient-rich loamy soil.

Solutions

  • Grow Cucumbers in a raised garden bed with a hand-prepared mix containing potting soil with peat-free compost, silt, perlite, and peat moss.
  • To prepare an organically rich soil mix, use organic compost or manure, preferably granules with a balanced NPK ratio of 10-10-10.
  • Water weekly to maintain good soil aeration and slightly moist condition.
  • Avoid using sand or clay potting mix that will harden over time.
  • Add lime to make the alkaline garden soil slightly acidic or neutral. It should be grown in rich organic soil with a pH between 6.0 to 6.5.

5. Low Temperature

Cucumbers are warmth-loving species that thrive in temperatures between 65 and 75°F (18 to 23°C) around the growing season.

Anything below 63°F will affect the fruit growth, and temperatures below 55°F will wither the plant, leading to cold stress.

Cucumber plants, especially those grown in colder climates, can succumb to temperatures low enough to cause a light frost overnight.

Yellowing of leaves, usually pale or whitish-yellow, can be an early indication of temperature stress.

When not treated in time, the plant will gradually fail to produce fruits or even die.

Solutions

  • Grow Cucumbers indoors if you are in USDA zones lesser than 4. USDA zones 4 to 12 are considered ideal.
  • Germinating Cucumber seeds require a temperature of 75°F, best attained in a warm location with ample sunlight or indoors under artificial grow light.
  • Germinate seeds indoors before moving them outside in late spring.
  • Choose raised garden bed located in a sunny location in the garden that receives at least 8 hours of sunlight each day.
Cucumber seedlings growing under grow light indoors
You can grow Cucumber seedlings indoors under grow lights.

6. Common Plant Pests

Yellowing Cucumber leaves may indicate pest infestation, like spider mites, whiteflies, potato leafhoppers, and aphids.

These sap-sucking insects feed on juicy Cucumber leaves, rendering yellowing hollow leaves.

The pests are more prevalent in spring and summer when the soil moisture is relatively high and plants are usually wet.

However, most pest infestations occur from using infected soil or introducing pest-infested plants.

PestsIdentification
AphidsCricket-like creatures with back legs that suck up saps from the undersides of leaves and stems.
MealybugsThey eat the leaves sap, causing stunted and deformed development.
ThripsSuck out plant's juice and leaves may appear pale, splotchy, and silvery before dying.
Spider MitesCausing leaves to turn yellow, brown, or gray and drop off.
Fungus GnatsSudden wilting, poor growth
Yellow coloration of leaves
Cabbage LoppersThey are small pale green caterpillars that chew holes in leaves.
Cucumber BeetlesLarvae feed on roots and adult insects chew leaves.
Damaged stems, leaves and petioles and scares in fruits.
Potato LeafhoppersThey inject watery saliva that damages the leaf surface
Yellowing and falling leaves

Solutions

  • Start with picking the visible insects from the leaves and dropping them in a soapy water solution.
  • Spraying the entire plant row with a mixture of Isopropyl alcohol and water may kill all kinds of pests.
  • Using a row cover may help prevent pests like Potato leafhoppers.
  • Otherwise, spray or wash the plant with insecticidal soap effective against all major bugs, but follow the guide to avoid killing beneficial bugs.
  • Make your garden clean and clear out all debris to avoid pest infestation.
  • Use horticultural and Neem oil to control the insect population.
  • Prune the infected plant to avoid further damage.

7. Horticultural Diseases

Although rare, horticultural diseases are often responsible for yellowing and yellowing spots on cucumber leaves.

The garden-grown cucumber plants are prone to get infected with seasonal diseases that will infect most vegetative plants.

Common Cucumber plant diseases include Mosiac virus, Verticillium wilt, Downy mildew, Fusarium wilt, Anthracnose leaf spot, and Powdery mildew.

Downy Mildew in Cucumber
Different fungal and bacterial infections may cause the yellowing foliage in Cucumber.

These diseases would mostly appear in Cucumber plants suffering from bacterial infection, infected soil, and wrong growing conditions.

DiseasesCausative Agent/ Symptoms
Mosiac virusIt is spread by aphids and other pests, leading to infected foliage with mottled appearance and yellow spots.

You would witness wrinkled and downward curves leaves
Verticillium wiltIt is caused by Verticillium fungi that survives in soil for years and activate whenever the soil is too soggy.

Chlorosis and red to purple discoloration of leaves are common indicators
Downy mildewIt is a type of water mold or foliar disease caused by Pseudoperonospora Cubensis that appears as fungi spread by spores.

You would witness light green to yellow angular spots on leaves
Fusarium wiltIt is caused by Fusarium oxysporum f. sp. cucumerinum that survives in soil for years.

It spread by water splash and infected tools, where you would see yellow around leaf edges
Anthracnose leaf spotAnthracnose leaf spot is a byproduct of Colletotrichum Orbiculare fungus, a pathogen that attacks cucurbits.

it may start with irregula water-soak leaf spots which turn yellow and later brown.
Powdery mildewPowdery mildew is a fungal disease that appears in warm and humid environment.

The spores can transfer to other plants via air and lead to powdery appearance on leaves, such as white patches and purple to reddish blotches.

Solutions

  • Start with quarantining infected plants in case of indoor plants and destroy or drop diseased plants as soon as possible.
  • Wash Cucumber plant leaves with a soapy water solution containing water and detergent.
  • Use systemic or contact fungicides, such as Bonide 811 Copper 4E Fungicide, early to prevent the progression of the disease.
  • Otherwise, use potent fungicides like Azoxystrobin, Flutolanil + Thiophanate-methyl, Tebuconazole, and PCNB to treat the infection effectively.
  • Clean the garden regularly and remove debris to prevent disease spread.
  • Prune weeds and sick-looking Cucumber leaves as a preventive measure.

Should I Cut Off Yellow Cucumber Leaves?

Yes, you can remove the yellow leaves on your cucumber plants.

Pruning yellowed and decayed leaves will help channel the energy towards healthy growth and fruits.

Removing spent leaves will help more sunlight reach the new fruits and foliage and improve air circulation for healthier fruiting.

However, you may need to determine the cause of the yellowing. The natural yellowing of leaves is normal around late summer or fall, which you can prune off.

Leaves completely yellowed or tanned should be removed immediately, but those with minimal yellowing can be reverted to green with immediate treatment.

Similarly, you should prune off pest and disease-infested leaves to prevent the further spread of diseases.

Encouraging regular pruning of Cucumber plants will help with healthy fruit production, but you must know what to cut off and what not.

Here are a few tips for pruning your Cucumber plant;

  • Prune the Cucumbers 3 to 5 weeks after they grow to allow vines to thrive well.
  • Remove decayed and yellow leaves regularly in spring and summer.
  • Remove leggy growth with small leaves and suckers every week.
  • Remove outside branches, leaves, and flowers, and develop fruits as needed.
  • Use isopropyl alcohol to sanitize the tool before and after pruning to prevent the spreading of fungal growth.

Tips to Care for Cucumber Plants

Cucumber plants are easy-to-grow and maintain annuals that will grow each year.

All you need to do is provide excellent care, essential maintenance, and a growth-appropriate environment.

1. Care Tips During Germination and Early Growth

  • Start with finding a south-facing site in the garden and create a raised garden bed with an appropriate soil mix.
  • Plant the seedling in spring when the risk of frost has already passed; otherwise, sow the seeds indoors for three weeks before transplanting them mid-spring.
  • Ensure the soil has organic matter, such as 2-inches of aged manure or compost, to a depth of 6 to 8 inches.
  • Ensure the soil temperature sits around 70ºF (21ºC), which is more like in mid-spring.
  • Plant each seedling 1 to 2 feet apart to allow proper growth and spread.

2. Care Tips During Fruiting and Later Growth

  • Ensure the plant gets 6 to 10 hours of sunlight each day.
  • Introduce trellis along the row if you are growing vining Cucumber plants.
  • Prune decayed foliage, flower, and fruits in the outer branch every week to improve fruiting.
  • Water early morning or afternoon, about 1 to 2 inches weekly, but avoid wetting the leaves.
  • Cover plants using row covers if bugs are prevalent in your garden.
  • Fertilize the plant with 5-10-10 solutions rich in iron and magnesium every three weeks in spring and summer.
  • For best results, maintain a humidity level of 85 to 95% in the garden by regularly spraying a fine mist of water around the plant.
Growing cucumber
Healthy Cucumber products will arrive within 50 to 70 days of sowing.

3. Care Tips During Harvesting

  • Pick fruits every couple of days in summer as they will proliferate.
  • Ensure to pick all the fruits before foliage turns yellow, making the fruits bitter in taste.
  • Pick regular slicing Cucumbers when they are about 6 to 8 inches long and burpless Cucumbers when they are about 10 inches long.
  • Remove all the fruits and decayed leaves before winter sets in to prepare for hibernation.

Conclusion

Yellowing of Cucumber leaves is expected due to Chlorosis and natural aging. However, excessive yellowing or browning with spots may indicate problems with watering, lighting, moisture, and pests.

Early intervention will help mitigate the problems and revert yellowing to avoid further damage.

Follow this guide to determine what may cause yellowing in Cucumber leaves, early diagnosis, and treatments.

Read more about other yellowing leaves problems in other houseplants.

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