- 3″ or 4″ cubes
- Small 25mm or large 40mm hole
- Can be used with jiffy pellets or rooting blocks
- High quality
- Made for easy root growth
- Highly porous
- Optimum drainage
Cultilene is one of the world’s most renowned producers of high quality substrates. They have a reputation in the hydroponics industry as a company that puts the grower first and thoroughly researches their products. All cultilene growing media products are completely pathogen free. Their fibres are made from smaller diameter fibres which enables a higher capacity for holding water. High porosity allows easy root penetration meaning your root system will spread and grow with ease. Good water movement & optimum drainage are 2 other benefits which will help your plant to thrive during its early life.
Some tips for use!!
Rockwool, sometimes referred to as stonewool, is a growing medium made of basalt melted back into lava and poured into a spinner in a process similar to making cotton candy. Basalt is arguably one of the most abundant materials on Earth and a large percentage of these rocks are above sea level. Most rocks and soil above sea level originate from a combination of basalt and granite, which has a strikingly similar chemical composition to basalt. As a growing medium, rockwool has been in use for more than 40 years and is one of the most commonly used substrates in commercial hydroponic productions across the world thanks to its inert properties, sterile start, and unique water-holding capacity. The best growing performances can be achieved with rockwool, but like with most high-performance things, a few details have to be right for maximum effect. The following guidelines contain some of the most common do’s and don’ts to help you make the most of your rockwool.
Do: Pre-soak Your Rockwool
Like most growing media, rockwool is shipped dry. There is 0% water in it when you buy it from the store. The initial wetting of rockwool, and actually all other media as well, is critical. Ideally, rockwool should be immersed in a nutrient solution adjusted to pH 5.5 until all the rising bubbles are gone. This will allow the water to infiltrate the tiny pores in the product and prepare the entire volume to be colonized by roots. The immersion time depends on the size of the block in question, from just a few seconds for tiny seed plugs, to several minutes for the largest products. In all cases, let the rockwool drain freely until water is no longer running out of it. Air will re-enter the largest pores, achieving the perfect balance between air and water in the medium. No squeezing or wringing is required.
Do: Keep the Wrap On Rockwool Cubes
Rockwool cubes, like most rockwool products are wrapped in an opaque plastic foil. This wrap has the same function as the walls of a plastic pot—it keeps the light out and the roots in. By covering the wool, it also prevents the growth of unsightly, yet harmless, algae. In the case of rockwool slabs, where the wrap encases the product completely, it also aids the initial pre-soaking, as most slabs will not fit in buckets or tubs. Nutrient solution fills the wrap like a bag until the slab is thoroughly wet. Only after that stage should you cut a drainage slit in the slab’s wrapping.
Do: Always Fertilize Your Rockwool
Rockwool does not lock out any fertilizer. All the nutrients present in the block will be in the solution available to the plant or ready to drain out the bottom. This means whatever nutrients you use will have an immediate effect on the plant, and any feeding mistake can be immediately corrected, allowing you to optimize your fertilizer use. If you irrigate with just water, the fertilizer concentration in the block will drop and may cause a slight shock to the plant. Rockwool has a tremendous capacity to retain water, so it is better to irrigate less often with a well-balanced nutrient mix than to water more frequently without the nutrients.
Do: Allow for Sufficient Run-off
Plants always take up water at a higher rate than nutrients, so expect some increase in the concentration of fertilizer salts inside the medium between waterings. Furthermore, not all nutrients are taken up by the plant at the same rate, which creates nutrient imbalances and modifies the pH over time. When the root zone is irrigated again, the water will push those nutrients down and replace them with the fresh nutrients it carries. If you never allow the substrate to drain sufficiently, the nutrients that were not consumed will accumulate in the medium, which may be unhealthy for your plants. Allow 15-30% of the volume of liquid going in to drain out the bottom of the medium to maintain optimal nutritional conditions in the root zone. Rockwool is the fastest and easiest substrate for this, but this principle applies to all media.
Do: Reuse and Recycle Rockwool
Although it is true that rockwool was originally manufactured as building insulation, horticultural rockwool shares few properties with the stuff that keeps your house warm in winter and cool in summer. Plants won’t grow in the insulation material because that material does not absorb water at all. The fact that the two materials look similar has given rise to urban legends regarding reuse, toxicity and disposal. At the end of the plant life cycle, horticultural rockwool can be reused to grow different plants, or you can shred it to be composted and then reused in potting mixes or in garden beds. Remember, rockwool is basalt, which is an excellent amendment for potted plants as crushed rock. Avoid using previously used rockwool to start plants, and also avoid reusing any growing media repeatedly to grow the same crop or crops within the same botanical family. To prevent issues due to the presence of rotting roots, you can simply treat the used rockwool with enzymes. Your local hydroponics shop employees can help you with this.
Don’t: Overwater Plants in Rockwool
Always fertilize the rockwool when you irrigate and allow for some drainage every time to wash off any excess fertilizer. The appropriate level of runoff should not exceed 30%, which means very little water should come out the bottom of a rockwool block. If you are watering and the amount of drainage exceeds 30%, you are probably overwatering. This may lead to algae growth. Most of the water volume in rockwool—as much as 85%—is available water for the plant, and the block can dry down to very dry conditions before the plant finds itself in water stress (as low as 10% in rockwool). The plant can literally tip over because the block is too light before you need to water again.
Don’t: Squeeze Your Rockwool
A common myth is that excess water in rockwool should be removed by squeezing the block or plugs. Do not do this! The structure of the fibers in rockwool contain beneficial water retention and air porosity properties that allow root systems to develop. Crushing the wool damages that structure and the air pockets that were initially present will never be restored. If rockwool is squeezed too much, the material will become a wet, soggy mess with no aeration whatsoever.
Consider the structure and porosity of rockwool to determine how tall a rockwool container can be. Problems arise when irrigation is attempted from the bottom. Water is subject to gravity and will not sufficiently wick up more than 5-6-in. above the water surface, which actually applies to most media, leaving the top of the container dry and the bottom soaking wet.
All of the roots will be at the bottom of the block looking for the water and most of the media volume at the top of the container will be devoid of roots. Stacking rockwool products higher in ebb and flow systems is not a problem as long as irrigation is applied from the top. Water must travel through the network of fibers that constitutes the wool, so the container can be as tall as needed to get enough root volume to sustain a plant.
Growers have an emotional attachment to their plants. They love, baby, spoil, water and fertilize them. Some religiously measure electrical conductivity and pH daily, and obsessively check for growth. Well, don’t…or at least back down. As mentioned earlier, rockwool has a huge water-holding capacity and all the fertilizer applied is available to the plant so it can often go for a long time without too much attention in the irrigation department. Don’t believe the myth that rockwool affects the pH of the nutrient solution. It is actually the natural process of the plant removing nutrients that raises the pH. If the plants are growing actively and are healthy, don’t obsess about the pH. It’s easy to correct it by changing the feed solution, but the pH can fluctuate from 5-7.5 without any ill effect on the plants. If you follow the guidelines in this article, you will find that rockwool is actually one of the easiest growing mediums to use. For more information, talk to the professionals at your local hydroponics shop. Happy growing!
Cultilene is committed to sustainable food production. Only if we use the available resources economically will we continue to be able to supply people worldwide with food. Our goal is to offer solutions to realize maximum food production of maximum quality with as little water and energy as possible. Cultilene supplies stone wool substrate solutions and Albarino diffused glass in more than 50 countries worldwide. The stone wool substrate is produced at 4 locations: Tilburg (The Netherlands), Gliwice (Poland), Castolovice (Czech Republic) and Paris – Ontario (Canada). The Saint-Gobain factory in Mannheim (Germany) manufactures the Albarino diffused glass.
Sustainable business practices are a common thread running throughout Cultilene’s operations: from raw materials to final products. We are sure that sustainability will give the greatest long-term benefits – for both our society and businesses! Cultilene operates in more than 50 countries where our local consultants work with you and your company to maximize your results. With their wide knowledge of the market and contacts in horticulture throughout the world, our specialists are valuable sparring partners for you as a business owner.
Cultilene feels a shared responsibility for your success. This is why be believe that sharing our expertise and experience with you as our customer is only natural. Our consultants do this on site at our customers’ locations, and we also have a highly informative website. This is where you can locate background information and whitepapers that provide additional information into specific topics about substrate and horticulture glass.