Why Are My Vinca Leaves Turning Yellow [Causes & Fixes]

The Vinca leaves turning yellow is uncommon and can be concerning because it indicates many underlying problems with the plant, including slow death.

Do not confuse it with natural aging and dormancy, which may also invite the yellowing of Vinca leaves.

Continue reading to discover what may cause Vinca leaves to turn yellow, how to identify them, and proven treatments.

5+ Reasons Behind Vinca Leaves Turning Yellow (With Solutions)

Vinca, also known as Periwinkle, is a popular evergreen plant widely grown in landscaping because of its intricate glossy green foliage and colorful flowers, which provide ample ground coverage.

But, sometimes, their leaves can turn yellow, especially potted Vinca. Remember, these plants do not turn yellow unless approaching winter (dormancy) or dying from old age.

Therefore, you must inspect the wrong growing conditions or environmental factors to diagnose untimely leaf yellowing.

1. Inappropriate Watering

Inappropriate watering is a significant concern for Vinca, as this drought-tolerant evergreen shrub efficiently preserves water.

Be wary about overwatering your Vinca plants, which can quickly lead to waterlogging, oxygen deprivation, and fungal rot.

Without timely treatment, the plant roots will turn dark and mushy, emitting a foul odor, further inviting the yellowing of foliage, stunted growth, and failed blooms.

The transpiring leaves can lead to drying and yellowing of foliage, sometimes accompanied by a browning and crispy appearance.

Treating Overwatered Vinca

• Pause watering immediately to allow the soil to dry out and prevent further damage.
• Remove any standing water from the Vinca plant’s saucer or pot.
• Inspect the roots by sliding the plant out of the pot and check for a dark, mushy, and smelly appearance.
• If the damage looks minimal, trim the infected roots, apply some fungicide, and repot in a fresh potting mix.
• Remove damaged and decayed leaves, flowers, and stems to save the plant’s energy.

Treating Under-watered Vinca

• Water the Vincas thoroughly until the excess water seeps out of the drainage holes.
• Throw away the water in the cachepot and let the plant dry naturally.
• Trim any damaged or crispy leaves, flowers, and stems to save the plant’s energy.
• Once the plant has recovered, adjust the watering schedule to prevent future issues.

For outdoor Vincas, water only when the soil feels dry one inch down or depending on the weather and season.

2. Too Much Sunlight

These drought-tolerant plants prefer full or partial sun, but it is given that exposure to intense sunlight will turn their leaves yellow or brown from excess transpiration.

You need not worry about some yellowing of garden-grown Vinca leaves in summer, which will revert to their original appearance later.

However, be careful about keeping potted plants in full sun during summer as they are more prone to drying and severe yellowing and wilting of foliage.

Sunburn can damage the plant and may cause the leaves to fall off.

On the other hand, growing them in the complete shade is an absolute No-No because their leaves will fail to produce chlorophyll or generate flower buds.

Quick Treatment Tips

• Move the potted plant to a shadier location or provide some shade to garden plants with a screen or cloth in high summer, usually zone 11 a or above.
• Remove any leaves or stems damaged by sunburn to prevent further stress on the plant.
• Water the plant because they need regular watering during hot or dry weather to compensate for the lack of moisture in the air.
• Apply a layer of mulch whole around the base of the Vinca to help retain moisture and keep the soil cool.

3. Wrong Soil pH

The wrong soil pH can affect Vinca plants in various ways, including causing nutrient deficiencies and limiting the plant’s ability to absorb essential minerals.

So, you should be wary about what soil mix and fertilizer you choose for your plant and how often you change the soil.

If the soil pH is wrong, the Vinca leaves will turn yellow due to nutrient deficiency, stunted growth, and poor flowering.

Quick Treatment Tips

• Test the soil pH: Use a soil test kit to determine the pH level of the soil to determine if it is too acidic or alkaline.
• Adjust the pH: If the soil is too acidic, add lime or wood ash to raise the pH level. If it is too alkaline, add sulfur or aluminum sulfate to lower the pH level.
• Re-test the soil: After adjusting the pH, re-test the soil to ensure it has reached the desired pH level.
• Amend the soil: If the potting mix or soil is too compacted or lacking in nutrients, add compost or other organic matter to improve the soil structure or consider repotting in a fresh mix.
• Create a perfect soil mix: Make a potting mix of mainly 50% compost, 25% sand, and 25% soil or any other recommended mixes.

4. Lack of Humidity

Vinca plant is a tropical species that thrives in moderate to high humidity levels, ideally around 50% to 70%.

They can tolerate various humidity levels, including moderately humid indoor environments.

You will likely witness browning leaf edges and yellowing of outer leaves when the humidity drops below 40%.

As the problem spreads, the leaves begin to transpire and change color to yellow and droop.

Be careful! High humidity levels, combined with poor air circulation, can lead to issues with fungal diseases, which invite root rot and yellowing of bottom leaves.

Quick Treatment Tips

• Place a room humidifier near the plant to increase the moisture levels in the air if you’re growing Vinca plants indoors.
• Ensure good air circulation around the plant by opening windows or adding a portable fan.
• Trim away decayed, dried, or brownish leaves to prevent further damage.
• Place the outdoor potted plant on a humidity tray to boost the humidity level in the air.

5. Nutrient Deficiency

The lack of nutrients will affect the plant’s overall growth, development, and flowering.

Remember, Vinca is very susceptible to iron and magnesium deficiencies, which leads to chlorosis or yellowing of leaves.

• Iron chlorosis begins at the tip of the leaf, while magnesium chlorosis is prevalent from the bottom.
• Vinca is also very sensitive to nitrogen deficiency and nutrient toxicities caused by over-fertilization.
• Similarly, a plant appearing stunted or failing to bear flower buds may indicate phosphorus and potassium deficiency.

On the other hand, over-fertilized Vincas are likely to bear yellow leaves with dark margins, leading to wilting and sometimes even death.

Quick Treatment Tips

• A soil application of elemental sulfur and iron chelates or a foliar spray of chelated iron helps treat iron chlorosis.
• Dissolve Epsom salt for Vinca in water and spray onto the leaves using a foliar spray to treat magnesium chlorosis.
• Apply a formulated nitrogen-rich fertilizer, such as 28-0-0 or 12-0-0, only once or twice to combat nitrogen deficiencies.
• Once the plant recovers, apply the best fertilizer for Vinca, such as All-purpose Fertilizer,  every 2 weeks or every 2-4 months from spring to early fall.

6. Cold Stress

Anything less than the minimum temperature will invite cold stress, which can leave vivid signs.

The prolonged stress can slow the growth and invite premature wilting and drooping of leaves.

You must step in early because plants exposed to cold temperatures will likely witness another season.

Quick Treatment Tips

• Immediately move your plant from the shade to a warmer location with direct sunlight, such as a south-facing window, patio, or garden.
• Cover the plant outdoors with a frost cloth or blanket to protect it from cold temperatures.
• Mulch the soil around the plant with manure, compost, or bark to help insulate the roots and protect them from the cold.
• Trim the affected leaves and stems only in spring when the plant grows actively.

7. Pests and Diseases

Indoor-grown Vinca plants are less susceptible to pests and diseases, but the same cannot be said for their outdoor counterparts.

These tropical plants are susceptible to sap-sucking and egg-laying pests like spider mites, aphids, mealybugs, scale insects, and whiteflies.

They can cause severe damage to your garden Vinca plants, often leading to yellowing leaves, stippling, mottling, distorted growth, and wilting.

Sometimes these pests are visible on the plant, and other times they leave visible damage on the leaves, stems, and flowers.

While outdoor Vinca is more likely to get infected, houseplants sharing space with outdoor plants are equally likely to get infected.

Quick Treatment Tips

• An early solution is to treat the plant with insecticidal soap, horticultural oil, or neem oil.
• Spraying with water to remove pests and eggs may also work sometimes.
• Use pesticides only if the infestation seems widespread and likely to damage other crops (Follow the manufacturer’s guide).
• Applying systemic fungicide on the affected leaves can also treat leaf spots and powdery mildew.

As a preventive measure, regularly inspect the plant for signs of infestation, trim bushy growths to allow air circulation, and maintain fertilizer intake to keep them healthy.