Mycology

You are very much correct. The mycelium loves cracked kernels as it has easy access to the starch. Since the kernels are hydrated, the shells aren't as much of a barrier in a 100% popcorn jar.

What I find curious is that the mycelium is actively avoiding kernels in a more preferential manner. Since the nutrition value is lower, a slower propagation on the kernels is expected. However, it's just nope'ing around the popcorn until it absolutely has no other place to jump to. It's cool to see that the preference is so distinct.

This begs another question though, and someone else pointed it out: How long do you need to store the spawn for? Slowing down mycelium growth could have its benefits.

Edit: Derp. I completely forgot why the shells can be preferred. If you have to shake or stir your spawn jar to distribute the mycelium, the shells keep the kernels from sticking together as hard.

I haven't tried with hominy, but I do have 10lbs of millet in spawn now.

Just speculation, but hominy may need to be pH adjusted and might be prone to getting too sticky and breaking down a little too fast. This might be an issue if you are spawning a bunch and need to shake the grains for even propagation.

Other than that, I just read on another forum that it spawns very quick.

Mixed cubensis genetics.

Popcorn is great when used alone without rice. I pre-cook it to ~60-80% hydration'ish, or when I can bite into it easily and the center has just started getting hydrated and isn't crunchy. I'll fill my spawn jars and load it in my pressure canner for about 90mins or so, depending on how many jars I have.

There are methods on YouTube for no pressure canner popcorn, so you can get away with a quick pasteurize it seems. Popcorn is obviously food-grade, so it's going to be fairly clean out of the bag.

So far, popcorn is also working awesome for pink and golden oyster spawn. Once Shiitake and Lions Mane get started, which takes a bit anyway, they do fairly well. I do want to experiment with adding peptone to the water when I pre-cook it to see if I can give it a little more "kick".

Price is variable and is only really cost effective with +50lb bags, if that is a concern. That is just about pinching pennies.

Mixed genetics cubensis. (It's of PE/JMF lineage; I don't want to get distracted in those details since it's not quite appropriate for this community.)

I wrote up more details in another comment, but yep, you just pre-boil the popcorn before sterilization. It's not cost effective in low quantities, btw.

Rye is the go-to and millet has a massive amount of surface area. I know rye will work but since it is a very well established grain to use, I want to explore other options as well. TBH, brown rice has been performing very well for me in all cases as well.

I have 10lbs of millet (split into 4 bags) that is getting close to 20 days or so. It started extremely slow, but once it took hold, the colonization has increased speed exponentially. I also have to break it apart more often to get more colonies established.