Is My Grow Contaminated?

Use this diagnostic guide to determine if what you're seeing is contamination or normal growth

Quick Check

✅ Probably Normal If:

  • ✓ Pure white color throughout
  • ✓ Thread-like or cotton-like texture
  • ✓ Fresh mushroom or earthy smell
  • ✓ Blue bruising when touched
  • ✓ Steady, predictable growth

❌ Likely Contaminated If:

  • ✗ Any green coloration
  • ✗ Black, orange, or pink colors
  • ✗ Sour, sweet, or rotten smell
  • ✗ Slimy or wet appearance
  • ✗ Growing faster than mycelium

Step-by-Step Diagnosis

Answer these questions about what you're observing to get a diagnosis:

Step 1: What color do you see?

Pure white
White is usually mycelium, but check texture
→ Continue to next question
Green (any shade)
⚠️ Trichoderma (green mold)
Action: Immediate disposal required
Black spots/powder
⚠️ Pin mold or Aspergillus
Action: Dispose with safety precautions
Orange/Pink/Red
⚠️ Neurospora (bread mold)
Action: Immediate disposal, deep clean area
Blue/Blue-green
Could be bruising or Penicillium
→ Continue to next question
Gray/Wispy
⚠️ Cobweb mold
Action: Treatable with hydrogen peroxide
Yellow/Brown wet spots
⚠️ Bacterial contamination
Action: Usually requires disposal

Step 2: What texture does the white growth have?

Dense, ropey, thread-like
Typical healthy mycelium structure
→ Continue to next question
Fluffy cotton-like
Common mycelium appearance
→ Continue to next question
Wispy, cobweb-like
⚠️ Cobweb mold
Action: Increase air exchange, apply H2O2
Slimy or wet
⚠️ Bacterial contamination
Action: Disposal recommended
Powdery
⚠️ Spore-producing mold
Action: Do not open container, dispose

Step 3: What does it smell like?

Fresh mushrooms/earth
Healthy mycelium smell
No smell
Normal, especially through containers
Sour/fermented
⚠️ Bacterial or yeast
Action: Check moisture levels
Sweet/fruity
⚠️ Yeast contamination
Action: May coexist, monitor closely
Rotten/putrid
⚠️ Severe bacterial
Action: Immediate disposal
Musty/moldy
⚠️ Mold contamination
Action: Identify type and dispose

Step 4: How fast is it growing?

Steady, 2-5mm per day
Typical mycelium growth rate
Very slow or stalled
Check temperature and moisture
Extremely fast (doubles daily)
⚠️ Aggressive mold
Action: Isolate and monitor
Overtaking mycelium
⚠️ Competitive contamination
Action: Disposal recommended

Step 5: Describe the blue coloration:

Blue where touched/damaged
Bruising - common in many species
Blue-green fuzzy growth
⚠️ Penicillium mold
Action: Early removal may work
Dark blue staining in substrate
Metabolite staining, usually harmless

Common Scenarios

White Fuzz on Grain Spawn

✅ Normal Signs:

  • • Even white growth spreading from inoculation points
  • • Ropey or rhizomorphic patterns
  • • Grains binding together
  • • Fresh mushroom smell

❌ Contamination Signs:

  • • Uneven patchy growth
  • • Different textures in different areas
  • • Wet, slimy appearance
  • • Any non-white colors

Surface of Bulk Substrate

✅ Normal Signs:

  • • White mycelium colonizing evenly
  • • Primordia (tiny pins) forming
  • • Some metabolite yellowing
  • • Blue bruising from misting

❌ Contamination Signs:

  • • Green patches appearing
  • • Gray cobweb-like growth
  • • Black spots or powder
  • • Slimy bacterial patches

Mushroom Fruits

✅ Normal Signs:

  • • Blue bruising on stems/caps
  • • Fuzzy feet (aerial mycelium)
  • • Spore deposits (dark)
  • • Natural cap colors for species

❌ Contamination Signs:

  • • Green mold on caps
  • • Soft rot or decay
  • • Unusual colored spots
  • • Slimy deterioration

What To Do Next

If It's Normal Growth:

  • • Continue normal care routine
  • • Maintain proper temperature and humidity
  • • Be patient - mycelium takes time
  • • Document progress with photos

If You're Unsure:

  • • Isolate the container from other grows
  • • Take clear photos for community help
  • • Monitor for 24-48 hours
  • • Look for changes in color or smell

If It's Contaminated:

  • • Do NOT open indoors if sporulating
  • • Seal in plastic bag before disposal
  • • Clean growing area thoroughly
  • • Review sterile technique
  • • Learn from the experience

Need Visual Examples?

Check our contamination types guide for detailed photos and descriptions of all common contaminations.

View Contamination Types Guide Browse All Troubleshooting

Remember:

When in doubt, throw it out! It's better to start fresh than risk contaminating your entire growing area.