As an avid gardener, seeing yellow spots or patches appearing on the leaves of your vibrant green plants can be distressing. However, yellowing leaves are often a symptom of an easily fixable issue. The key is to diagnose the underlying problem accurately and take appropriate action. Here are some of the most common causes of yellowing leaves and how to remedy them:
Overwatering – drainage
One of the most frequent culprits of yellow spots is overwatering. While most plants require moist soil, too much water deprives the roots of oxygen and can cause root rot. The solution is simple – allow the soil to dry out before watering again. For potted plants, you may need to repot with fresh well-draining soil to prevent excess moisture buildup.On the other end of the spectrum, yellow leaves can also indicate that the plant needs more water. Water the plant thoroughly until water drains from the holes in the bottom of the pot. The soil should be damp but not soggy. Watering needs will vary based on factors like plant type, pot size, and weather.
Nutrients lacking – fertilize regularly
A lack of important nutrients like nitrogen, sulfur or iron is a common cause of yellowing leaves. Use a balanced fertilizer once a month during the growing season to provide nutrients. For an iron deficiency, specifically, you can spray the leaves with a chelated iron foliar spray. The plant can then absorb the iron directly through the leaves.
Pests or disease – inspect, treat, remove
Yellow spots, especially if irregular or concentrated on leaf edges or leaf tips, can sometimes signal a pest infestation or fungal/bacterial disease. Inspect the leaves closely for signs like spots, lesions, webbing, stippling, mold or deformities. Treat insect pests with horticultural oil or insecticidal soap. Remove badly infected leaves. For disease, you may need to use a fungicide or bactericide, depending on the specific problem.
Light insufficient – move to sunlight
If lower leaves are turning yellow, the plant likely needs more light. Move the plant to a spot with direct sunlight exposure for at least 6 hours a day. South or west-facing windows are optimal. If outdoor light isn’t possible, supplement with a grow light placed 3 to 16 inches above the leaves. LED grow lights are energy efficient and can cover a few houseplants to an entire indoor garden. Provide 14 to 16 hours of additional light per day until the plant regains its green foliage.
pH unbalanced – test, adjust as needed
An improper soil pH prevents your plant from accessing nutrients, often shows as yellow leaves. The ideal pH range is 6 to 7 for most common houseplants. Test your soil using an electronic meter or strip tests 2 hours after watering. If the pH is not in the target range for your specific plants, you’ll need to adjust it using sulfur or lime.
To lower soil pH (make more acidic), sprinkle in 1 teaspoon of agricultural sulfur per gallon of soil and retest in 4 weeks. Retreat if pH remains imbalanced.
To raise soil pH (make more alkaline), use dolomitic lime at 1 teaspoon per gallon of soil. Retest in 4 weeks and reapply if below target pH.
Normal pH will permit proper nutrient absorption so your plant leaves regain healthy green coloration. Re-check pH at the start of each growing season.
By inspecting your plant closely, you can determine the likely cause of yellowing leaves and take steps to correct the issue. Address any problems with watering, nutrition, light or pest management and your plant should soon return to a healthy, lush green. With regular monitoring and care, yellow spots on leaves can usually be avoided or caught and solved early.