Your monstera’s leaves are turning yellow. Your pothos has brown spots. Your fiddle leaf fig is dropping leaves like confetti. Before you panic — or worse, overcompensate with more water — let’s diagnose what’s actually happening.

Here are the 10 most common houseplant problems, what causes them, and exactly how to fix them.

1. Root rot

Symptoms: Yellowing leaves starting from the bottom, mushy brown roots, soil that stays wet for days, a sour or musty smell from the pot.

Cause: Overwatering or poor drainage. The roots suffocate and fungal pathogens (usually Pythium or Phytophthora) take over.

Treatment:

  • Remove the plant from its pot immediately
  • Trim all brown, mushy roots with sterilized scissors
  • Let the remaining roots dry for 1–2 hours
  • Repot in fresh, well-draining soil with a pot that has drainage holes
  • Don’t water for 5–7 days, then resume with a reduced schedule

Prevention: Always check that the top 1–2 inches of soil are dry before watering. Use pots with drainage holes. Add perlite to soil mixes for better drainage.

2. Powdery mildew

Symptoms: White, powdery coating on leaves and stems, distorted new growth, leaves that curl or brown at the edges.

Cause: Fungal infection caused by poor air circulation, high humidity near leaf surfaces, and moderate temperatures. Common on begonias, African violets, and jade plants.

Treatment:

  • Isolate the plant immediately
  • Remove heavily affected leaves
  • Apply neem oil spray (1 tsp neem oil + 1 tsp dish soap + 1 quart water) every 3–5 days
  • Improve air circulation around the plant

3. Leaf spot diseases

Symptoms: Brown or black spots on leaves, sometimes with yellow halos, spots that may expand and merge.

Cause: Bacterial (Xanthomonas, Pseudomonas) or fungal (Alternaria, Cercospora) infections, often triggered by overhead watering or poor air circulation.

Treatment:

  • Remove affected leaves and dispose of them (don’t compost)
  • Water at the base of the plant, not from above
  • Apply copper-based fungicide if the problem persists
  • Ensure good spacing between plants

4. Overwatering symptoms

Symptoms: Yellowing leaves (especially lower leaves), soft and mushy stems, mold on soil surface, fungus gnats, leaves that feel heavy and waterlogged.

Treatment: Reduce watering frequency. Let the soil dry between waterings. Improve drainage. Consider repotting if the soil is compacted and waterlogged.

5. Underwatering symptoms

Symptoms: Crispy brown leaf edges, leaves curling inward, dropping leaves, dry crumbly soil that pulls away from pot edges, lightweight pot.

Treatment: Water thoroughly until water runs out the drainage hole. If the soil has become hydrophobic (water runs straight through), bottom-water by placing the pot in a tray of water for 30 minutes.

6. Nutrient deficiency

Symptoms: Pale or yellowing leaves (nitrogen), purple-tinged leaves (phosphorus), brown leaf edges (potassium), yellowing between leaf veins (iron/magnesium).

Treatment: Apply a balanced liquid fertilizer at half strength. For specific deficiencies, use targeted supplements. Feed during growing season (spring/summer) every 2–4 weeks.

7. Spider mites

Symptoms: Fine webbing on leaf undersides, tiny stippled dots on leaves, leaves that look dusty or bronzed, overall declining vigor.

Treatment: Spray leaves with a strong stream of water to dislodge mites. Apply neem oil or insecticidal soap every 5–7 days for 3 weeks. Increase humidity — mites thrive in dry conditions.

8. Scale insects

Symptoms: Small, oval, brown or tan bumps on stems and leaf undersides. Sticky residue (honeydew) on leaves. Sooty mold may develop on the honeydew.

Treatment: Remove visible scale with a cotton swab dipped in rubbing alcohol. Apply horticultural oil or neem oil. For severe infestations, consider systemic insecticide.

9. Sunburn

Symptoms: White, bleached, or brown patches on leaves that face the sun. Crispy, papery damaged areas. Sudden appearance after moving a plant to a sunnier location.

Treatment: Move the plant to indirect light. Remove severely damaged leaves. Acclimate plants gradually when increasing light exposure — move them 30 minutes closer to the window each day over 2 weeks.

10. Edema (oedema)

Symptoms: Raised, corky bumps on leaf undersides. Looks like blisters or scabs. Common on succulents, geraniums, and jade plants.

Cause: The plant absorbs water faster than it can transpire, causing cells to swell and burst.

Treatment: Reduce watering frequency. Increase light and ventilation. This condition is cosmetic — it won’t kill the plant but affected leaves won’t recover.

When to use AI diagnosis

If you’re unsure what’s wrong with your plant, take a clear photo of the affected area and use GardenGenius’s disease diagnosis feature. The AI can distinguish between conditions that look similar — for example, bacterial leaf spot vs. fungal leaf spot, or overwatering vs. root rot — and provide targeted treatment recommendations.

The difference between a dead plant and a thriving one is often just knowing what’s wrong early enough to act.