Introduction to Grodan stone wool

Stone wool, also known as wool, rock wool or mineral wool, is made from basalt, which is solidified lava spewed from the innermost depths of the earth. In its manufactured state, stone wool can have multiple purposes, such as an insulation solution or a growing medium. Stone wool growing media used for cultivation of plants in Controlled Environment Agriculture (CEA) is pH-neutral and has air pockets that make it suitable for hydroponics, as plants need oxygen and moisture in their root zone. This type of soilless, inert growing media is ideally suited to indoor cultivation, from vegetables and floriculture to medicinal crops.

The origin of stone wool

Stone wool was discovered on the islands of Hawaii around the beginning of the nineteenth century and occurs as a natural byproduct of volcanic activity. Grodan invented and debuted stone wool as a growing media in 1969, and in the decades since then, our company has led the way in advancing indoor growing technology. We love to share our knowledge on best practices for rapid root development, crop growth, and how to achieve consistent, efficient production and maximum yields with minimal resource inputs.

Grodan offers a wide range of stone wool growing media products. Our cultivation system consists of plugs, blocks and slabs. The plug is used for sowing, where the seed grows into a seedling. Then the seedling with the plug is transplanted in a block in which it is grown into a full-fledged young plant. The full-fledged young plant with block is then placed on the slab for growing to maturity and producing fruits. 

When implementing Precision Growing focused on the root zone a grower will aim to influence the rootzone environment throughout the entire cultivation cycle. Every crop will go through 6 distinct growing phases. Maximise your crop’s potential with data-driven cultivation. In addition to our GroSens sensors and our e-Gro software platform, Grodan provides its customers with crop and slab specific user advice for each growing phase within the 6-Phase Model.

Our wide range of innovative growing media are suited for vegetable propagation and growing, specifically for tomato, cucumber, sweet pepper and eggplant crops as well as leafy greens and culinary herbs.

We also have a crop-specific range of growing media for floriculture. Our focus is on rose and gerbera. These crops are characterised by their perennial cultivation properties.

To accommodate different stages of crop production, Grodan offers stone wool plugs, cubes, blocks and slabs for medicinal crops.

The use of stone wool growing media offers many advantages. Thanks to the controlled manufacturing process, this growth medium is of a consistently high quality. The sterile production under extreme temperature ensures that the product is clean. Its unique fibre also makes the cultivation on stone wool growing media very easy to control. The grower can administer the precise amount of water and nutrients the crops need in a very directed and controlled manner, to achieve optimal growing results. Waste becomes a thing of the past. Efficient use of water and nutrients keeps yield per square metre high, and energy consumption per unit of product low. Additionally, the growing media is lightweight, making it easy to handle. And last but not least, stone wool can be easily recycled into raw materials for products such as new stone wool and bricks.

Growing crops without soil means growing them reliably. Because everything can be controlled. Every decision made in the greenhouse or growing room today has a major impact on tomorrow's results. Grodan provides a total solution, supporting our deeply-rooted knowledge with our digital solutions to improve cultivation on stone wool from root to fruit.

What happens when making stone wool? It is made from basalt, which is solidified lava spewed from the innermost depths of the earth. To produce stone wool, extracted basalt and raw stone material is re-liquefied in furnaces at a temperature of 2700° Fahrenheit/ 1500° Celsius. The molten rock is injected with air and spun into a fibrous, yet light consistency resembling spun sugar. The material is treated with a hydrophilic binder to facilitate liquid absorption, which ensures even distribution of water and nutrients upon use. Next, it is congealed in a hardening kiln using hot air at > 390° Fahrenheit/ 200° Celsius after which it is compressed into wool packets.

The stone wool packets are then cut into a graduated series of sizes and shapes—from small-sized plugs to larger blocks and slabs - each designed for various crops and for different stages of crop production. The finished products are wrapped in a special film that blocks UV light and limits the growth of algae on the growing media surface.

The result is a unique, uniform and inert growing medium that is sterilized of pathogens, including mold or mildew, with plenty of space for roots to grow and access moisture, nutrients and oxygen from well-distributed irrigation. Clean stone wool is designed to retain water as well as air, while also promoting healthy drainage from top to bottom - unlike soil-based media that are prone to compaction and certain soilless media that can become hydrophobic (water-repelling) if allowed to dry out.

For a more elaborate insight into our production process, please see these videos.

The main difference between stone wool, coco coir, peat and soil growing media is that stone wool is mineral-based, not carbon-containing organic matter. It’s made of natural stone, not coconut husks, bog-sourced peat moss or the composted wood byproducts found in most potting soils.

Because stone wool is heated to such extreme temperatures (about 3,000 degrees Fahrenheit/ 1500 degrees Celsius) during the manufacturing process, it’s a hygienic, clean growing media free of pathogens. It’s also fully compatible with hydroponic and automated growing systems, as well as automated irrigation technologies that rely on precise control.

Stone wool is a highly suitable growing medium for Controlled Environment Agriculture, or indoor cultivation environments. This closed environment, in combination with stone wool and automated growing systems, allows for every aspect of the plants’ lighting, nutrition and irrigation to be controlled by the grower. Stone wool products are designed for precision growing and are fully compatible with the sensors and automation tools utilized in a data-driven cultivation strategy.

Is stone wool more sanitary than soil, peat, or coco coir?

Another reason Grodan products are popular with propagators and growers is that stone wool is a clean growing medium.

Stone wool is much less likely to be contaminated by fungi, yeasts and bacteria as well as insects and microbes that feed and live on carbon-based organic matter in coco coir and soils. Therefore enhancing crop quality.

In addition to the naturally clean qualities of stone wool, Grodan also wraps its products in a protective film that discourages algae growth and makes for easier handling.

Sustainability profile of stone wool

Grodan has profiled itself for many years as a company with an active policy of corporate social responsibility. Sustainability is therefore an integral part of our company philosophy. Care for humans and the environment is evident in every stage of the life cycle of our growing media solutions, from production, primary use, and recycling into secondary markets post-harvest.

The growing media we have innovated to support soilless cultivation is made of stone wool – a clean and recyclable material formed of abundant basalt rock. It's thanks to this material that soilless growing places minimal strain on our world's precious resources, using less fertiliser, 50% less water and 75% less land that can be given back to nature to rest and rewild.

How can we help you?

Grodan supports growers overseeing operations of all sizes with data-driven cultivation tools  and sustainability-minded crop steering techniques for high-tech indoor and greenhouse environments. How can we help you?