HB4 Worm Based High Performance Substrate
Five or ten pounds of perfectly hydrated substrate, pasteurized, ready to mix with your colonized grain. Coco coir, vermiculite, gypsum, and worm castings, balanced to field capacity. No manure smell. No guessing hydration levels. Break it up, layer it in your tub or tray, and watch your mushrooms grow.
We use worm castings instead of horse or cow dung. Same slow-release nutrients that dung-loving species need, but cleaner to work with and less contamination risk.
Stable batch to batch so you can dial in your Tek. This is the formula that took first place at a Denver growers competition in 2024.
Pair with our Multi Grain Matrix sterilized grain pre-spawn. One 4 lb bag of grain per 10 lb bag of HB4 makes one 32-quart monotub or 2x 10x20 nursery trays.
Ships hydrated, sealed in Unicorn 5 micron filter patch bags. Store at room temp for up to 6 months until opened.
What's in the Bag
Coco coir, vermiculite, gypsum, and worm castings. Pasteurized, hydrated to field capacity, and sealed in a Unicorn 0.2 micron filter patch bag. No manure, no smell.
Specs & Hydration
Weight: 5 lbs (1x bag) or 10 lbs (1x bag). Ships at field capacity. Squeeze test: 1-2 drops means perfect hydration. If substrate appears dry, mist with distilled or RO water before use.
How to Use (Spawn to Bulk)
Layer in your tub: 1 inch of HB4 on the bottom, break up your colonized grain pre-spawn on top, then another inch of HB4. Seal the tub and let it colonize for 10-14 days at 72-78F. Move to fruiting conditions once you see full colonization.
Shipping & Guarantee
Ships within 24 hours via USPS Priority. Free shipping on orders over $50. If your substrate arrives contaminated, we replace it at no cost.
What's Inside
Four ingredients. Dialed in.
The Mix
Our HB4 blend: pasteurized, hydrated to field capacity, sealed at the lab. No manure.
The Result
What happens when the formula meets your mycelium.
Need grain to go with it?
Complete the grow.
HB4 is the substrate. Pair it with grain pre-spawn to start your tub.
All in One Mushroom Grow Bag for Multiple Flushes
Everything in one bag. Grain + substrate + injection port.
Multi Grain Matrix (4 lbs)
50/50 millet and rye. Inoculate, colonize, then mix with HB4.
Common Questions
Before you buy.
What species work with HB4 substrate?
Dung and coir loving species. Our worm casting blend provides the nutrient profile these species evolved to thrive on. Not intended for hardwood-loving gourmets like oyster, lion's mane, or shiitake.
How much grain pre-spawn do I need per bag?
One bag of our Multi Grain Matrix (4 lbs) pairs with one 5lb bag of HB4. For the 10lb bag, use two grain bags. Higher spawn ratios colonize faster and reduce contamination risk.
What's the spawn-to-bulk ratio?
We recommend 1:1 to 1:2 spawn-to-substrate by volume. A 1:1 ratio colonizes faster. A 1:2 ratio stretches your grain further but takes longer. Start with 1:1 if you're dialing in your tek.
Why worm castings instead of manure?
Same slow-release nutrients that dung and coir loving species need, but cleaner to work with. No smell, lower contamination risk, and more consistent batch to batch. This formula took first place at a Denver growers competition in 2024.
How do I check if hydration is right?
Squeeze a handful. If 1-2 drops come out, you're at field capacity. HB4 ships hydrated, but if it looks dry after storage, mist with distilled or RO water before use. Never use tap water.
Why is HB4 good for dialing in my tek?
Consistency. HB4 performs the same batch after batch, so when you change a variable like species, spawn ratio, or fruiting conditions, you know the substrate isn't the variable. That's how you isolate what's working and optimize your grows.
What Growers Say
Hear it from the grow room.
Join the Club
The Grower's Club
Strain notes, troubleshooting guides, and harvest showcases from real growers. Starts in your inbox, grows from there.
No spam. Just grows. Unsubscribe anytime.