What is the Best Grain Spawn to Substrate Ratio?

So you’ve got a jar of fully colonized grain spawn. Now what?

Click here to skip the jazz and get right to it.

Spawning to Bulk:

Referred to as the spawn to bulk ratio, this measurement is referred to in terms of volume, NOT weight. (learn about that conversion here)

Therefore a ratio of 1:1 would be 1 (unit of volume) of spawn, to 1 identical unit of volume of the substrate. A lower ratio is one where which uses closer to equal parts of spawn i.e. 1:1 and a higher ratio utilizes more substrate than spawn. 

When birthing your spawn to a bulk substrate the ratio of substrate to spawn you use will have a major impact on the success and/or failure of your grow.

For instance, having a higher ratio of 1:8 (1 part spawn:8 parts sub) will result in more bang for your buck in colonized spawn, AKA spawn spread over more substrate,  which may lead to higher yields per lb. of grain. However, a ratio this high will severely impact colonization times, thus increasing the potential for contamination and loss. 

The ratio you use will also depend on the type of mushroom you are growing and the substrate used. Oyster mushrooms, for example, thrive on a straw-based substrate and can use a ratio of anywhere from 1/5 all the way to 1/20!

This article will focus on manure-loving species, but if you would like to read more about straw-lovers cab be found here.

So what spawn to bulk ratio should you use?

In my humble opinion, it doesn’t pay to be a spawn penny pincher. Especially if you are a beginner or working in less than cleanroom conditions.

Bottom line:

The lower the ratio (1:1,1:2) the faster the colonization, lowering chances for contamination, and increased likelihood for multiple flushes.

I would not advocate anything above 1:3 for a beginner.

More experienced cultivators can get away with much higher ratios. I have personally found that anything above 1:5 to be a crapshoot.

What are your thoughts? What ratio have you used with the highest success?