Inoculating the Substrate
Introduce mushroom spawn to the substrate to begin growth.
- Use fresh, high-quality spawn from a trusted supplier.
- Mix spawn into substrate at 10–15% by weight.
- Spread the mixture evenly in containers or outdoor beds.
Maintaining and Monitoring Portobello Growth
Consistency and attention are essential during growth.
- Maintain steady temperature and humidity.
- Mist the substrate as needed; avoid overwatering.
- Watch for contamination like mold or foul odors.
- Look for mushroom pins and primordia as signs of fruiting.
- Maintain fresh air and humidity around 90% during fruiting.
- Add a 1–2 inch casing layer (peat moss or vermiculite) on top to retain moisture and stimulate fruiting.
Harvesting and Enjoying Your Portobello Mushrooms
After several weeks, you’ll be ready to harvest.
- Harvest when caps reach 4–6 inches in diameter.
- Gently twist or cut mushrooms at the base—don’t pull.
- Use immediately in dishes like burgers, pasta, or risottos.
- Store in paper bags in the fridge for up to a week.
Ideal Temperature Ranges
- Best range: 55–70°F (13–21°C).
- Optimal: around 65°F (18°C).
- Don’t exceed 80°F (27°C); avoid anything over 85°F.
Best Soil Conditions
- Use manure-based compost mixed with soil and peat moss.
- Fill 6 inches with compost in an 8-inch deep bed, top with peat/soil mix.
- Grow indoors in dark, cool spaces like a basement (65–70°F).
- Outdoors, use shaded areas where days are below 70°F and nights above 50°F.
Signs Your Portobellos Are Ready to Harvest
- Caps are fully open and 4–6 inches wide.
- Caps are brown and firm to the touch.
- Gills are visible but not yet darkening.
- Stems are thick and mature.
- Avoid harvesting once gills turn inky or the cap becomes slimy.