How to Inoculate Straw with Grain Spawn

Before starting this project, check out our Practical Guide to Mushroom Gardening for an overview of the different stages of mushroom cultivation. In this post, we're doing a deep dive into how to inoculate straw with grain spawn.

Once your straw is draining, it's time to prepare for mixing in the grain spawn! For this step, you'll need:

• Grain Spawn - Contains live mycelium that turns straw into mushrooms
• Gloves - Single use or reusable gloves prevent skin irritation from sanitizers
• Mixing Table - A folding table or any surface covered with a tarp that can be easily cleaned
• 70% Isopropyl Alcohol - For sanitizing everything that touches straw or grain spawn, you can order it on Amazon or pick up at Ace Hardware if you head there to get Hydrated Lime
  
• Cropping Containers - This can be mushroom grow bags, 5 gallon buckets with holes drilled in it, used nursing pots that have been washed out, or poly tubing (more on this later)

Prepare Work Surfaces

Before spreading out your straw, sanitize all work surfaces and supplies with 70% isopropyl alcohol. This includes your gloves, bags of grain spawn, and any other tools you plan to use, like scissors or your cropping containers if you're reusing old containers. Next, spread straw out onto your mixing surface. Avoid overcrowding the table or piling the straw high, this can make mixing difficult or cause it to fall off the table.

Mix in Spawn

Break up the Grain Spawn while it's still inside the bag and spread it evenly over the pasteurized straw at a ratio of at least 1:10 by weight. Be careful with any large chunks of grain spawn when pouring it over the straw, they're prone to rolling off the table! While wearing sanitized gloves, break up any chunks of grain spawn as you mix it evenly throughout the straw. Any straw or grain spawn that falls off the table should be discarded - this makes for great mulch!

If you're using our recommended supplies, 2 bags of grain spawn is plenty to inoculate 1 bag of Standlee Chopped Straw. Generally speaking, you'll want to use an amount of grain spawn equal to 40% of the dry weight of your straw. For example, 25 pounds of straw calls for 10 pounds of grain spawn.

Note: Most commercial growers use a 1:20 spawn ratio, but that often leads to contamination or low yields for home gardeners. If you're just starting, a 1:5 (20%) spawn ratio is the most reliable.

Pack into Cropping Containers

After mixing, pack the spawned substrate into your cropping containers. We recommend food-safe 5 gallon buckets with 1/4" holes drilled every 6-8 inches. They're stackable and reusable, but if you're wanting to be even more frugal you can stuff the straw into used nursing pots that have been cleaned and sanitized.

• Grow Bags – Use Type 3B (5-micron filter) for best air exchange.
• 5-Gallon Buckets – Should have aeration holes drilled for proper airflow.
• 16" Poly Tubing – Good for larger grow logs. Poke small aeration holes spaced 6-12 inches apart with a simple broad arrowhead. A utility knife works in a pinch to cut X-shaped holes instead.

Incubating Your Mushrooms

Once you've got your mushrooms inoculated and packed into their containers, it's time to incubate for 7-14 days at room temperature. Check out our detailed guide for more info!