Boost Your Mushroom Harvest: Substrate Additives That Actually Work

Whether you're growing for research, personal exploration, or microdosing protocols, the substrate you choose—and how you enhance it—can make a dramatic difference in how well your psilocybin mushrooms grow. If you're cultivating in Denver, Colorado, with its unique dry climate and high elevation, dialing in your substrate with the right additives is key to getting strong colonization, healthy fruiting, and heavy flushes.

Why Supplement Substrate?

Psilocybin-containing mushrooms like Psilocybe cubensis thrive on nutrient-rich substrates. While many growers use basic coir/vermiculite (CVG) blends, supplementing with targeted additives can:

• Speed up colonization

• Increase fruit size and flush volume

• Improve resistance to contamination

• Help the substrate retain moisture longer — especially important in dry climates like Denver

Top Substrate Additives for Psilocybin Mushroom Growth

1. Gypsum (Calcium Sulfate)

• Purpose: Gypsum adds calcium and sulfur, essential for healthy mycelial metabolism and enzyme production. It also helps break up substrate clumps and improves moisture distribution.

• Use: 2–5% of dry substrate weight. Common in grain prep and bulk mixes.

2. Worm Castings

• Purpose: A natural source of nitrogen, beneficial microbes, and minerals. Adds texture and nutrition without dramatically increasing contamination risk.

• Use: Blend ~10–20% into your bulk substrate for improved structure and nutrient balance.

3. Manure

• Purpose: P. cubensis evolved to grow on dung, so supplementing with aged, properly leached manure can enhance performance and replicate a natural environment.

• Use: Often mixed with coco coir and vermiculite in a 1:1:1 ratio. Always pasteurize.

4. Spent Coffee Grounds (used sparingly)

• Purpose: High in nitrogen and carbon, they can give a small nutrient boost.

• Use: Max 5–10% of substrate. Must be pasteurized and mixed thoroughly—coffee is highly contaminant-prone.

5. Fungi Fuel (Denver-Formulated Booster)

• Purpose: This mix includes a balanced blend of hydrolyzed protein, beneficial microbes, and trace minerals. Formulated specifically for psilocybin mushroom cultivators in dry, high-altitude environments.

• Use: Mix with distilled water as a flushing enhancer

Popular Substrate Recipes for Psilocybin Mushrooms

Classic CVG (Coir/Vermiculite/Gypsum)

• 650g coco coir

• 2 quarts vermiculite

• 1 cup gypsum

• Hydrated to field capacity

High-Yield Dung Mix

• 1 part pasteurized aged horse manure

• 1 part coco coir

• 1 part vermiculite

• 5% worm castings

Pro-Tip: Add hydrated lime (calcium hydroxide) in small amounts (~0.2%) to stabilize pH for certain high-yield varieties.

Why This Matters in Denver

With low humidity and swings in indoor temperature, psilocybin growers in Colorado face specific environmental challenges. Supplementing with ingredients like gypsum, worm castings, and Fungi Fuel helps:

• Retain moisture longer during dry spells

• Encourage aggressive colonization (reducing contamination windows)

• Increase fruit body size even on second or third flushes

In Summary: Small Additions = Big Results

By intelligently supplementing your substrate, you can supercharge your psilocybin grow. You’ll see:

• Faster colonization times

• Larger, denser fruits

• Healthier mycelium

• Greater yield over multiple flushes

We carry everything you need in-store and online—pre-pasteurized manure substrate, coco coir, vermiculite gypsum, and Fungi Fuel are all available for pickup or shipping across the U.S.

Ready to Upgrade Your Grow?

Stop by either of our Denver Metro shops to chat with us, we’ve tested these recipes and additives in real-world grows. Or order online and get growing!