Organic Gypsum | Grain & Fruiting Substrate Supplementation
Organic Gypsum | Grain & Fruiting Substrate Supplementation
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Maximise your harvest potential with our Regular Grade Gypsum (Calcium Sulphate), a premium organic mineral additive specifically selected for optimising mushroom fruiting substrates. While our fine-grade version is specialised for grain spawn, this regular grade Gypsum offers a more economical solution for large-scale substrate preparation without sacrificing quality for both grain and bulk/fruiting substrate. It serves as a fundamental supplement that ensures your mushrooms have the structural and nutritional foundation required for high-yield flushes.
The Role of Gypsum in Substrate Optimisation
In the fruiting stage, the physical consistency of your bulk substrate is vital. Integrating Gypsum into your mix—whether you are using coco coir, straw, or hardwood pellets—helps prevent substrate clumping and improves aeration. This improved structure allows for better water distribution and oxygen exchange, creating the ideal environment for robust mycelium development. Chemically, gypsum acts as a pH buffer, stabilising the environment as the mycelium grows and metabolic byproducts are produced.
Pure Nutrition for Professional Results
Our organic Gypsum is 94% pure and provides a potent source of essential minerals:
- 23% Calcium: Strengthens fungal cell walls and aids in the transport of nutrients.
- 17% Sulphur: Supports enzyme activity and protein synthesis for vigorous growth.
Whether you are a hobbyist cultivating at home or a professional grower managing a commercial facility, using Gypsum in your substrate preparation is a proven method to enhance mushroom production and overall fruit body quality. By choosing our 94% pure organic sourced gypsum, you ensure your cultivation setup remains free from unwanted synthetic additives, keeping your gourmet mushrooms as natural as possible.
Benefits
Benefits
- Calcium Enrichment: Gypsum supplies vital calcium, strengthening cell walls and supporting healthy mushroom growth.
- Improved Substrate Structure: By preventing clumping, gypsum ensures a loose, aerated substrate, facilitating efficient colonisation.
- pH Stabilisation: Gypsum helps maintain a stable pH level, creating an optimal environment for mycelium proliferation.
How do I use it?
How do I use it?
Incorporate up to 5% gypsum by dry weight into your mushroom substrate mix for best results. For example, add 50 grams of gypsum to 1 kilogram of dry substrate components.
Available Sizes
Available Sizes
250g – Great for hobbyists & small batches
500g – Ideal for regular growers
1KG – Cost-effective for ongoing projects
2KG – Best value for larger or frequent grows
Delivery Information
Delivery Information
- We ship from Tamborine Mountain, QLD using either AusPost or Aramex
- Fast dispatch within 1-2 business day (excluding Fridays) with express post options available
Why Customers Love Us
Australian Owned
Family Business
Sustainability

Hand-Grown on Tamborine Mountain
At Kai Kai Farm, we don't just sell kits and tonics—we use them every day. Founded by Quintin and Amy in the heart of the Scenic Rim, our mission is to make professional-grade mushroom cultivation and sustainable gardening accessible to everyone. From our no-spray gourmet mushrooms to our bio-active soil health range, every product is tested right here on the farm to ensure your growing journey is a success. When you shop with us, you’re supporting a local family business dedicated to a greener, more delicious planet.
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