Are white spots a sign of overwatering?
Written by
Nguyen Minh
Reviewed by
Prof. Charles Hartman, Ph.D.White leaf spots do not usually arise solely from the condition of overwatering. While the occurrence of soggy soil can damage roots, surface ailments like fungi or mineral deposits are usually what create the identifying spots. I have diagnosed gardens where panic-watering circumstances made outbreaks worse. Be aware of leaf textures, that is generally if a spot is crisp, it likely is related to environmental stress and not drowned roots.
Fungal Growth
- Powdery mildew thrives in humid, stagnant air
- Appears as flour-like dust on leaves
- Worsens with nighttime moisture
Pest Activity
- Spider mites leave stippled white dots
- Mealybugs create cotton-like residue
- Check leaf undersides with a 10x lens
Mineral Buildup
- Hard water leaves chalky residue
- Fertilizer salts crystallize on edges
- Wipe leaves with vinegar solution monthly
Edema
- Overwatered plants burst cells
- Creates water-soaked white blisters
- Improve drainage with perlite or sand
To avoid future outbreaks, water plants at the base. A client with a rose bush had to stop treatment for spots when switching to drip irrigation. When watering properly in the morning, the leaves should be drying up around noontime. Use pots made of terra-cotta for potted plants, they will wick moisture.
Treat confirmed fungal infections with the use of a baking soda mix. The simple recipe is the following: mix 1 teaspoon of baking soda, ½ teaspoon of soap, and 1 quart of water. Then spray every five days until the spots disappear. I saved a lavender plant after my neighbor's overwatering spread spores, and I treated the lavender plant this way.
Don't be tempted to water on a schedule. Instead, put your finger in the soil 2 inches, and if it feels damp wait before watering. Overwatering deteriorates roots, traps fungus gnats, and their larvae feed off rotting roots. If you have fungus gnat adults in the soil, place yellow sticky traps on top of the soil while correcting watering habits.
Read the full article: White Leaf Spots: Causes and Solutions
