Dealing with begonia problems? From brown flowers to pests and mildew, here’s how to diagnose issues and fix them fast to keep your begonias thriving.

Buds Drop Usually Because of Improper Moisture; Temperature Changes

Bud dropping may be caused by too much or too little water, especially if plants are allowed to completely dry out between waterings. Although tuberous begonias do best when the soil surface dries out slightly between waterings, try not to let them dry out completely. A sudden temperature change from hot to cold or vice-versa also causes buds to drop.

Flowers Spotted; Petals Transparent Caused By Improper Watering

Begonia flowers can be damaged by water spots due to improper watering. Petals show brown spots or transparent blotches where water drops have soaked in. Shield blossoms when misting containerized plants. Outdoors, water tuberous begonias in the garden with a drip system or a hose than drips directly into the soil. Avoid overhead sprinkling.

White Coating On Leaves Caused By Powdery Mildew

Powdery mildews are caused by fungi that live on the surface cells of plants. Infected begonia leaves will be covered with a white or ash-gray powdery mold. Badly infected ones become discolored and distorted, then drop off. Powdery mildews thrive in both very humid or very dry weather. Spray affected plants thoroughly with wettable sulfur once or twice at weekly intervals starting as soon as the whitish coating of the fungus appears. Allow ample spacing between plants and collect and discard all above ground refuse in the fall. Many newer varieties are resistant.

For more information see the file on Controlling Fungal Disease

Leaves Covered With Gray Mold Caused By Gray Mold

Gray mold is a fungal disease that often results from poor ventilation, insufficient light or high humidity. Remove faded flowers, a common spawning ground for the disease. Plant begonias in a well-ventilated location in light, rather than deep, shade. If the growing season is especially humid, gray mold may appear despite precautions. In such a case, destroy infected plant parts, and spray buds and blooms with flowable sulfur fungicide every 3 to 5 days.

For more information see the file on Controlling Fungal Disease

People aslo ask:

Why Are My Begonia Flowers Turning Brown?

Begonia flowers can turn brown due to several common issues:

1. Overwatering & Root Rot – If the soil stays too wet, roots rot, leading to brown, limp flowers. Fix: Use well-draining soil and let the top inch dry out before watering.
2. Underwatering & Drought Stress – Dry soil causes brown, crispy spots on petals. Fix: Keep soil consistently moist but not soggy.
3. Fungal Diseases (Botrytis Blight, Powdery Mildew) – Brown, fuzzy spots on flowers often mean fungal infections thrive in humid conditions. Fix: Improve air circulation, remove infected flowers, and apply a fungicide.
4. Sunburn & Heat Stress – Direct sunlight can scorch petals, turning them brown. Fix: Move begonias to bright, indirect light and avoid mid-day sun.
5. Low Humidity – Dry air causes flowers to brown and shrivel. Fix: Increase humidity with a pebble tray or misting.

Prevent begonias from turning brown by balancing water, avoiding direct sun, and controlling humidity.

What Are Begonia Diseases?

Begonias can suffer from various diseases caused by fungi, bacteria, viruses, and nematodes.

Here’s how to identify and manage them:

1. Fungal Diseases (Most Common)

• Powdery Mildew – White, powdery coating on leaves and stems.
  Fix: Improve airflow, reduce humidity, and use a sulfur-based fungicide.
• Botrytis Blight (Gray Mold) – Flowers turn brown with fuzzy gray mold.
  Fix: Remove infected parts, improve ventilation, and apply a fungicide.
• Leaf Spot Diseases – Brown or tan spots on leaves, often caused by Cercospora begoniae.
  Fix: Remove affected leaves and avoid overhead watering.
• Root & Crown Rots – Wilting, decline, and plant collapse due to Rhizoctonia or Pythium rot.
  Fix: Ensure well-draining soil and avoid waterlogged conditions.

2. Bacterial Diseases

• Bacterial Leaf Spot – Small, blister-like lesions on leaves.
  Fix: Remove infected leaves and avoid splashing water.

3. Viral Diseases

• Impatiens Necrotic Spot Virus (INSV) – Brown ring spots and mottled yellow leaves.
• Tomato Spotted Wilt Virus (TSWV) – Leaf curling, discoloration, and stunted growth.
• Cucumber Mosaic Virus (CMV) – Mottled, distorted leaves.
  Fix: Remove infected plants; no cure exists for viral diseases.

4. Nematode Problems

• Foliar Nematodes – Yellowing, leaf lesions, and necrosis.
• Root Knot Nematodes – Galls on roots, stunted plant growth.
  Fix: Use nematode-resistant soil and remove severely infected plants.

Prevent Begonia Diseases: Ensure good airflow, avoid overwatering, and regularly inspect plants for early signs of disease.

What Causes Brown Spots on Begonia Leaves?

Brown spots on begonia leaves are often caused by watering issues, fungal infections, pests, or environmental stress. Overwatering leads to root rot and fungal growth, while underwatering causes dry, crispy spots.

Too much direct sunlight can scorch leaves, leaving brown patches, while poor air circulation and sudden temperature changes can also stress the plant. Pests like mealybugs and whiteflies feed on plant sap, creating brown spots as damage spreads.

To fix the issue, keep soil moist but not soggy, provide bright, indirect light, inspect for pests, and use a fungicide if needed. Ensuring good airflow and stable conditions will help keep your begonias healthy and spot-free.

Why Are My Begonias Dying?

Begonias often die due to overwatering, which leads to root rot, causing wilting, yellowing, and mushy stems. If the soil stays too wet, the roots suffocate, leading to plant decline. On the other hand, underwatering can cause dry, crispy leaves and overall weakness. Always check the soil moisture before watering—the top inch should feel dry but not completely parched. Using well-draining potting mix and pots with drainage holes can prevent water-related issues.

Light and humidity also play a key role in begonia health. Too much direct sunlight scorches leaves, while too little makes them leggy and weak. Bright, indirect light is ideal, and maintaining moderate to high humidity prevents leaves from drying out. If your environment is too dry, use a humidifier, pebble tray, or occasional misting to keep the air moist.

Pests like mealybugs and aphids, along with fungal diseases, can weaken begonias, leading to stunted growth and browning leaves. Regularly inspect your plants, remove infected leaves, and use appropriate treatments like insecticidal soap or fungicides. By balancing water, light, and humidity while keeping an eye on pests, you can revive your begonias and prevent future issues.

• Begonia Buds Turn Black
• Tuberous Begonia Fell Over While Being Watered
• Begonia Leaves Are Curling
• Begonia Leaves And Stalks Are Turning Red
• Begonias From Garage Have Large Sprouts
• Begonia Leaves And Flowers Turning Black At Edges
• Begonia Leaves Are Very Pale
• Begonias Have Started To Topple With Stems Just Falling Off Main Plant