5+ Reasons for Poinsettia Leaves Turning Yellow

The Poinsettias are grown for their traditional glossy red flowers and green foliage; therefore, you can tell something is awfully wrong with them when the foliage starts turning yellow.

Poinsettia (Euphorbia pulcherrima) is a beautiful tropical flowering plant from Central American forests.

Be wary about growing Poinsettia because the green foliage turning yellow is quite an uncommon sight.

Why are my Poinsettia Leaves Turning Yellow and Falling off? (Reasons & Solutions)

Although they bloom in winter, these plants are not cold hardy and may suffer in cold temperatures.

Similarly, inappropriate watering and lack of light and nutrition are other major culprits behind sickly yellow leaves.

Here are some root causes of problems Poinsettia plants and ways to mitigate or treat them.

1. Inappropriate Watering

Poinsettias are tropical plants that thrive in moist soil; hence, regular watering in the growing season is a must.

However, they despise sitting in a pool of water, which is more prevalent in houseplants.

Overwatering is the primary culprit behind yellowing leaves because too much water will deprive the plant roots of oxygen and nutrients.

Poinsettias need to dry out between each watering. Overwatering can invite fungal and root decay problems due to excess moisture.

As a result, the Poinsettia roots will falter, and leaves will turn floppy as they fail to produce food.

The leaf veins start turning lighter than the rest of the leaf as the discoloration gradually spreads throughout.

Like overwatered plants, underwatered Poinsettias will begin to wilt and turn yellow with browning edges.

However, there are seeming differences between the two.

• The underwatered leaves would curl but turn floppy like the overwatered plant.
• In addition, the yellowing will start from top-to-bottom as the leaves begin to turn crisp from transpiration (loss of water from the leaves).
• Moreover, the plant loses its upright structure and starts drooping; the soil may look dry and cracked.

Immediate Solutions

• For overwatered plants, immediately stop watering and set them in a warm place to recover.
• Prune off heavily affected foliage with excess yellowing and floppiness and flowers.
• If the condition does not improve in a week, inspect for root rot problems by sliding out the plant and checking for root decay signs.
• Trim off brown, mushy, and smelly roots, apply fungicide, and transplant in a fresh, well-draining potting mix.
• For underwatered plant, run the pot under the distilled or fresh water until excess starts to run out of the drainage holes and set it in a sunny location.
• Otherwise, submerge the pot in a container filled with water to allow the soil to absorb it through osmosis.
• Resume watering the plant when the top 1-2 inches of soil dries out.

Preventive Measures

• Make a schedule for watering your Poinsettia once a week with about 1 inch of water throughout the spring and summer.
• Use a soil moisture meter or insert your finger to check whether the top 1-2 inches of soil has dried before watering.
• Use distilled, rainwater, or freshwater for watering purposes.
• Cut back on watering in fall and winter to once every two weeks or only when the soil feels dry.

2. Cold Temperature

Poinsettias are not cold-hardy plants; therefore, they will suffer in freezing temperatures, usually below 50°F.

Remember, if you have kept your plant near a drafty window or on the patio where they are more likely to experience cold, especially in fall.

You would witness the leaves begin to droop as they change color from green to pale or whitish yellow.

Therefore, a cold, stressed Poinsettia is less likely to bear new foliage and flowers.

On the other hand, the warming temperature can have slightly different effects, making Poinsettia leaves turn crispy.

It is due to excess transpiration and lack of humidity essential to maintain a healthy, whole leaf.

Immediate Solutions

• Start correcting temperature issues: move your plant away from the drafty window, outdoor location, and near AC or heating units.
• Move them to a warm and humid indoor location, usually under LED grow light with a room humidifier, to adjust the temperature stress.
• Trim off heavily affected leaves to redirect the energy towards healthy growth.

Poinsettia leaves should begin recovering within a week. You can set them in an open window or area when the last spring frost passes.

Preventive Measures

• Poinsettias prefer an indoor temperature of a steady 65-75°F.
• Avoid keeping them close to direct sunlight or heating units, which can spike temperatures above 90°F.
• Add a room humidifier to maintain the ambient humidity level between 50-75%.

3. Not Enough Lighting

Poinsettia is a shade-loving plant that ideally grows in medium to bright light but in direct sunlight.

However, these plants are also photoperiodic, requiring extended periods of complete darkness to blossom.

Therefore, do not mistake their short demand for complete darkness for year-round lighting requirements.

Poinsettias deprived of optimal lighting will fail to produce chlorophyll, leading to green pigment loss on leaves.

These leaves often exhibit pale, yellow leaves that look droopy, and new growth will fail to flourish.

On the other hand, too much light will increase transpiration, leading to dried, curled leaves with browning edges.

In most cases, the yellowing of Poinsettia foliage is caused by a lack of sunlight.

Immediate Solutions

• Move the plant to the east-facing window for yearly light balance or a few feet away from the south-facing window.
• Remove the affected leaves (yellowed, curled, or excessively browned) using a sterilized pruning shear.
• If it is already winter, let them sit in the darkness to help bloom new flowers.

Preventive Measures

• Care to provide 8-10 hours of bright indirect sunlight throughout spring and summer.
• Avoid keeping them close to the south-facing window to prevent the risk of sunburn.
• Add drapes or shades in the window to filter the amount of light that passes to the plant.
• Alternatively, use full-spectrum artificial grow lights if the sunlight is scarce.

4. Excess Fertilization

Although providing a nutrient boost helps attain healthy growth and white, pink to red flowers, applying too much fertilizer, especially during winter, can stress the plant.

Remember, fertilizing the plant during the bloom or winter can lead to mineral buildup around the roots.

As the roots fail to obtain oxygen, water, and healthy microorganisms, the leaves will turn yellow with a crispy texture.

Sometimes, the affected young-leaved may fall as the plant fails to circulate water and oxygen.

Immediate Solutions

• The best solution is to flush excess nutrients by running fresh water throughout the soil multiple times.
• Cut back on fertilizing until the plant recovers or not until spring.
• Prune off excessively yellowed or wilted leaves to reduce stress on the plant.

Preventive Measures

• Avoid feeding your Poinsettias when they begin flowering, usually in winter.
• Provide formulated fertilizer with NPK 15-0-15 or 15-16-17 monthly in spring and summer.
• Dilute the fertilizer with water in a 1:1 ratio (1 part water, 1 part fertilizer) to minimize the risk of chemical burns.

5. Powdery Mildew

Although rare, homegrown Poinsettia may encounter powdery mildew when the growing conditions are wrong.

A relatively high humidity (greater than 90%), low light, and warm temperature may risk the chances of encountering fungal diseases like powdery mildew.

The white powdery substance will appear on the infected leaves, eventually turning yellow, brown, and falling off.

You are more likely to invite powdery mildew on Poinsettia when you wet the leaves when watering the plant.

Immediate Solutions

• Start with removing heavily infected leaves that look yellow or brown with a sickly appearance.
• Mix 1 tsp. Baking soda with 1-quart water and spray the solution over the plant to kill the fungus effectively.
• Alternatively, you can apply biological fungicides like Serenade to destroy fungal pathogens without harming the plant.

Preventive Measures

• Ensure optimal air circulation inside the room and use a room humidifier set at 60-70%.
• Avoid wetting the leaves when watering.
• Never water the plant in the noon or evening, which may lead to soggy soil.
• Choose a location with medium to bright light.

6. Pest Infestation

Be wary of common garden pests like aphids, whiteflies, spider mites, scales, and fungus gnats that feed on plant sap leading to the sickly-looking plant.

The infected foliage will produce spotted, yellow, and disfigured leaves that will lead to the deterioration of the plant.

These pests often lead to vivid signs on the plant, such as:

• A white web-like substance underside of the leaves indicates spider mites.
• Green waxy bumps on the leaf undersides indicate scale insects.
• Fungus gnats and whiteflies will conceal themselves in leaf axils and look like tiny cotton wool.

The Poinsettia leaves will become disfigured with tiny holes, drop new growth, and change color to yellow or brownish shade.

Immediate Solutions

• Start by trimming the heavily infected leaves.
• Dab the cotton swab in rubbing alcohol and wipe the infected.
• Otherwise, spray the plant with liquid insecticidal soap or a solution of 1 tbsp. liquid baby soap with 1 liter of water.
• Applying neem oil over the plant can stop pests’ spread and effectively kill the pest eggs.

Preventive Measures

• Avoid overwatering the plant, which invites soggy soil conditions.
• Maintain the humidity level below 70% to prevent wetting the foliage.
• Avoid bringing garden plants, freshly cut twigs, grasses, or weeds inside the house.
• Clean the plant leaves every 1-2 months using soapy water or neem oil to ward off any pests.