5LB / 2.2KG Sterilised Master Straw Mix Mushroom Substrate | Fruiting Block | Williams Co Supplies

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5LB / 2.2KG Sterilised Master Straw Mix Substrate | Fruiting Block

5LB / 2.2KG Sterilised Master Straw Mix Substrate | Fruiting Block

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 Ready to use
 50% Straw 50% Soy
 5lb / 2.2kg per bag
 Sterilised & Contaminant Free
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A remix of the tried and tested king of substrates, the masters mix. This highly supplemented substrate ensures a high-yielding first flush!

We have seen great harvests of all Oyster & Agaricus species using this substrate. 

We make the masters mix fruiting blocks by first mixing 50% straw and 50% soy hulls (with a couple of extra secret ingredients) and hydrating them to the correct moisture content. We then load each heavy-duty grow bag with the mix, heat seal them and sterilise at 15psi for 120 minutes in our commercial autoclave.

We take great pride in our attention to detail and techniques ensuring you will receive nothing but the best possible product.


  • Open the sealed bag and mix with colonised grains at your chosen ratio
Delivery Information

Your order will be sent with Royal Mail or Parcelforce, you will receive an email once it has been dispatched. Orders are dispatched within 2 days unless stated otherwise. Plain packaging.

30 Day Money Back Guarantee

We offer a money back or replacement guarantee on all of our products. To claim your replacement or refund please send us photos of the issue to: support@williamscosupplies.com and we will do our best to help you.