StoneWool Grow Blocks for Commercial Hemp and Cannabis Growers

Posted on May 4, 2020 by Red Rock Block

Stone-wool and Hemp: A Combo for High Yields and Excellent Growing Seasons

Ever since Denmark in the late 1960’s conducted testing on a construction insulation known as stone wool, the hydroponic industry has never been the same! This material made from the extreme melting of basalt rock into thin, yet strong fibers is a great medium for hemp. No matter the strain or variety, stonewool can be used throughout the whole life cycle of hemp. Commercial growers great and small with a wide range of hydroponic systems have found larger yields at a quicker pace when compared to other growing media.

What is stonewool and how is it made specifically? 

Stonewool is also known as mineral wool and is one of the most widely used grow media in the commercial hydroponic industry. It is also a great material for smaller scale growers showing many benefits.

This material wasn’t always used for growing plants. In fact, this material has it’s origins in the construction industry with insulation. When the basaltic rock was melted and spun into thin fibers and wrapped into sheets, builders found that the insulating properties of the material were excellent for all buildings. Then in the 1960’s Denmark researchers conducted studies on the ability of stone wool to support crop growth. After these studies, stone wool was further developed and engineered to support plant growth even better! Now it is one of the top media to grow plants no matter the scale. 

The process is relatively simple. The material is produced by melting basaltic rock and spinning the molten material into the thin fibers which are cooled by a stream of air. These fibers are molded into many different shapes that growers can use in their operations from plugs, cubes, slabs, and blocks. Although this is a man-made substrate, the material is often regarded as a natural product as it came originally from rock.

Using Stonewool in Hydroponics


When growing in stonewool, it is important to adjust the pH as the stonewool is naturally alkaline. After a 24 hour soak in water, the material is ready to use for hemp as the pH should be around 5.8-6.3. Using stonewool in a hydroponic system and converting to stonewool is a fairly simple task.

The cubes and blocks can be cut to size to fit into a system and can go from the smaller plugs for crops like lettuce to buckets for larger crops like hemp and tomatoes.

Stonewool in a hydroponic system has many benefits that make it the better alternative to traditional methods of cultivation. Oftentimes with other media such as coco coir, the system can become clogged and backed up preventing the flow of water to crucial areas of the system. Stonewool is tightly woven and does not degrade in a system. 

Stonewool Container Types and The Best Stage of Growth for Use


An additional benefit of stonewool is the readiness of seedlings to root to the material. Smaller cubes and plugs are ideal for starting from cuttings and seeds. Once the roots begin to sprout through the bottom of the plug, the plants are ready for transplanting to larger cubes or blocks. Transplanting with stone wool is very simple and easy.

A grower can either transplant into pre-cut holes in the slabs or blocks or cut a custom sized hole for the plants. By placing the smaller block into the space and pinning until roots grab a hold of the new space is all a grower needs to transplant. This method is ideal to preserve roots and ensure minimal root breakage. It is because of this that the plants are not stressed and do not slow in their growth. The ability to place these plugs or smaller cubes into the larger material is also ideal from a space and organization standpoint. If there comes a time that the material becomes root bound, the grower can always transplant into a larger block or slab with the same method  with plugs.  

The Best System for Stonewool in Hydroponics 


Even though many growers associate stone wool with the more advanced hydroponic systems such as NFT, DWC, and flood systems, this substrate can be used with top fed systems as well as hand watering. Slabs of stone wool are preferred by larger commercial cultivators, but a grower can also grow much larger crops in an oversized block. In a drip irrigation system, the stone wool substrate is placed into the plastic containers, just as coir or clay stones are with a nozzle from the drop irrigation line. Drip irrigation systems and stone wool perform well together as many plants dislike over-watering and with the excellent moisture retention of the material and the precise water application of the drip lines, this duo is seemingly unstoppable. Stonewool can also float along the surface of water for deep water culture systems or those that use aquaponics systems. In Nutrient Film Systems (NFT), the stone wool plugs are placed in the predetermined slots. 

Suggested Fertilizers for Stonewool 

As stone wool is made from rock material, this substance is inert and contains no additional nutrients. The material is more basic or alkaline so pH should be monitored. With these points in mind, it is important to use fertilizers that are pH perfect. Even though the grower with this inert material has full control over the nutrient contents of the growing area, the material can be easily over fertilized. Fertilizing needs to be controlled and done so with close monitoring which should be an automatic good habit of a grower. Close monitoring of nutrients and plant needs helps to fully understand and monitor plant growth.

Quality Stonewool Products

An important factor of using stone wool to grow commercial hemp, is to use quality materials from reputable manufacturers. By going with a trusted source, a grower can be rest assured that the material they are purchasing is expected quality. RedRock stone wool products are perfect for large scale commercial production. With different sized starter plugs to larger grow blocks, these stone wool cubes are easy to transplant into a convenient insertion area in the grow block. Studies have shown that the use of these new stonewool grow blocks have an increase in root growth when compared to standard stonewool grow blocks used in hydroponics. 

Give us a call today for more information about ordering RedRock Blocks premium-grade stonewool grow blocks. Call- 1-310-967-2025

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