Brown Spots on African Violet Leaves: Multiple Causes, One Careful Diagnosis
African Violet (Streptocarpus sect. Saintpaulia (formerly Saintpaulia ionantha))
Symptoms
- Brown spots or patches of varying shapes on the leaf surface
- Concentric ring-pattern brown spots (ring spot from cold water)
- Irregular tan-to-brown water-soaked spots with a gray fuzzy center in wet conditions (Botrytis)
- Bleached then brown areas on the side of leaves facing a window (sunburn)
- Brown leaf tips or margins (fertilizer salt burn or low humidity)
Causes
Cold water contact causing ring spot (most common)
Ring spot is the most common cause of brown spots on African Violet leaves. Cold water droplets on the warm, velvety leaf surface create ring-shaped or irregular pale brown to tan marks where the temperature differential kills leaf cells. These marks are permanent but cosmetic. The pattern — clear rings or patches matching the shape of water droplets — is distinctive.
Botrytis cinerea (gray mold) in humid conditions
Botrytis causes tan or grayish-brown water-soaked spots that develop a characteristic gray fuzzy spore coat in moist conditions. It typically starts on damaged, dead, or weakened tissue — spent flowers left on the plant, damaged leaves, or injured tissue from cold or drought — and spreads. Unlike ring spot, Botrytis spots may spread and merge, affecting healthy surrounding tissue.
Direct sunlight burning leaf tissue
Direct afternoon sun through a south or west window creates bleached then brown zones on the leaf surface facing the window. These marks are harsher in appearance than ring spot — more of a bleaching or scorching rather than a ring pattern — and are concentrated on one side of the plant.
Fertilizer salt burn on leaves or roots
Splashing fertilizer solution on leaves or using too-concentrated fertilizer can cause brown spots or tip burn. Salt accumulation at the leaf margin (from wicking of concentrated fertilizer) produces brown edges and tips progressively over time.
How to Fix It
- 1
Identify the spot pattern before treating. Concentric rings or circular patches matching water drops = ring spot (cold water). Gray fuzzy coating = Botrytis. One-sided bleached-to-brown zone = sunburn. Brown leaf margins from inside outward over time = salt burn.
- 2
For ring spot: spots are permanent. Remove badly marked leaves, switch to room-temperature bottom-watering permanently. New growth will be spot-free.
- 3
For Botrytis: immediately remove all affected leaves, spent flowers, and dead tissue from the plant and dispose of them outside. Apply a fungicide (thiophanate-methyl, mancozeb, or copper-based) to the plant. Improve air circulation around the growing area. Reduce humidity at the plant level.
- 4
For sunburn: move the plant away from direct sun or add a light-diffusing filter, since African Violet's fuzzy leaves scorch faster in direct rays than a smooth-leaved plant would. The burned spots themselves are permanent, but leaves that unfurl after the light is corrected will come in clean.
- 5
For fertilizer salt burn: flush the soil thoroughly with plain water to wash out accumulated salts. Reduce fertilizer concentration to one-quarter to half the label rate. Remove damaged leaves.
Prevention
- Bottom-water only, using room-temperature water — prevents ring spot completely
- Keep in bright indirect light without direct sun hitting the leaves
- Remove spent flowers promptly — dead flower tissue is the most common Botrytis entry point
- Maintain good air circulation to prevent Botrytis-favorable humid stagnant air
- Fertilize at half strength or less to prevent salt accumulation
Quick Summary
| Plant | African Violet (Streptocarpus sect. Saintpaulia (formerly Saintpaulia ionantha)) |
|---|---|
| Category | Disease |
| Likely causes | Cold water contact causing ring spot (most common), Botrytis cinerea (gray mold) in humid conditions, Direct sunlight burning leaf tissue, Fertilizer salt burn on leaves or roots |
| Fix steps | 5 steps — see above |