Hi Karen,

You might find that this works a few of times, especially if the spawn is vigorous and well colonised before you expand it again, and if you use it at a high rate.

The times that I have done this I’ve found mixed results – sometimes it worked well but the majority of the time it resulted in some green mould in the new substrate. I think this happens because some mould spores are present (although not at all visible) in the substrate being used as ‘spawn’.

This is the problem with expanding a ‘spawn’ source likely to contain other organisms other than the Oyster mycelium. When you break it up and mix it into new substrate there’s a chance you also give other species (especially blue/green moulds) to prosper as well. This is why spawn is normally a pure mushroom culture growing on a steruile substrate – so you can be sure of what you are expanding.

That’s not to say it’s not worth trying though – I’ve definitely had a good number of successes like this and it can save a lot of money on buying new spawn. I think the key if you do it would be to use it at a very high ratio of 1:2 or 1:3 as you suggest.

Let us know how it goes!
best wishes, Adam 🙂

Hey Julian,

welcome to the forum! Yes, when we began growing on coffee back in 2011 we used to use shredded card mixed in and had pretty good success like this for a couple of years. It breaks up the mix reasonably well and if your coffee is very wet it can be added dry and will help to soak up the extra moisture.

Most of the the time though it is best to soak the card in water for an hour or so first (freshly boiled water is ideal to pasteurise it). Then, when it has cooled, squeeze any excess water out and add to the mix at up to 20% of the coffee volume. If you add it dry, most of the time you will create a very dry mix that the mycelium will struggle with.

The main reason we stopped using shredded card was to do with scale and consistency – we wanted a material that was easier to pasteurise/soak in bulk and would mix consistently when on a larger scale. The cardboard tends to clump up in the mix quite a lot so it didn’t work so well in larger batches. Also, whenever we experienced contamination, we suspected the card was the most likely source, so we switched to using straw which gave a much better mix and next to no contamination.

In summary – yes shredded cardboard can work well at a smaller scale and is obviously really easy and cheap to source. Give it a go, and try to pasteurise and squeeze out excess moisture before using.

best wishes, Adam

• This reply was modified 9 years, 3 months ago by Adam.

Nice idea Lee, we’ll look into it 🙂

cheers, Adam

Hi Lee,

hardwood pellets are ideal if you can source them, but we’ve found them difficult to get hold of in the UK, and have had good results just using softwood pellets. Their main function is creating a more open structure in the coffee mix, but we’ve also grown Oysters in bags of 100% softwood pellets as well.

It’s possible that some of the resin content is reduced in the pellet production process under high heat/pressure, and also Oysters are just really versatile and will grow on lots of materials that other mushrooms won’t, so you should be fine with softwood pellets.

best wishes, Adam

Hi Phae,

the sun’s UV rays don’t usually stop mushrooms from growing, but low humidity certainly can – so I’d guess that it was either the drying affect from the sun or some other unknown factor. If you can post a hoto here or send to support@growmushroomsoncoffee.com I’d be happy to take a look and offer some further thoughts.

best wishes, Adam

Hi Alvin,

we have actauuly not yet trialled it ourselves as we’ve beeen unable to easily source any so far from the couple of coffee roasters near to us.

Not sure if Shaun has grow with any yet though?

Hi Ying, and welcome to the course!

You can grow up to around 20-25% of the substrate weight over 2-3 crops if you re-soak the substrate (overnight in water) in between harvests.

We have found that it is possible to grow at least 2kg mushrooms per m2 every week if you cycle growing bags in and out of the space after just 2 harvests. The 3rd harvest is usually much smaller, so it is better to use the space for new bags than to maxiumise the yield per bag if you are limited in space.

hope this helps.
best wishes,
Adam