How to use Grow Cubes

Rockwool could be a mainstay growing media for commercial hydroponics growers, primarily those that implement drip irrigation systems. Originally used as insulation and also called rock wool or stone wool, Rockwool was developed in Denmark back within the 1970s for gardening. It retains moisture well, it retains oxygen well, it never impedes root growth, it’s chemically inert, and it comes in a very form of sizes and shapes. These benefits contribute to its popularity amongst growers, accommodating almost any plant they’re growing.

What are Rockwool Cubes?

Similar in texture to wire wool, rockwool may be a dense mat consisting of long strands of natural fibers. Basalt rock and chalk are combined so melted at a really extreme temperature (approximately 3000°F) to create lava. Then people throw the lava into a spinning chamber to form the fibers in an exceedingly process very similar to making candy.

Due to the firing process, rockwool cubes are chemically and biologically inert. This creates a perfect growing medium for hydroponic growing systems.

After the fibers are spun, they’re mixed with a binding agent and pressed into large mats. The mats are then delved into various sizes of cubes and slabs to be sold to customers as a growing medium for plants.

Rockwool cubes are popular hydroponics growers, likewise as conventional growers thanks to their beneficial structure. When the fibers are spun it creates a structure that’s perfectly suited to retain water while holding more oxygen than typical soil mediums. The increased water holding capacity and oxygenation within the foundation zone are exceptionally beneficial when starting seeds and rooting propagation cuttings.

Another benefit to rockwool cubes is that they are considered to be a natural product while they’re imitations. this is often because they originate from basaltic rock and chalk which are natural ingredients. Being considered a natural product makes them acceptable in organic growing systems, increasing their popularity.

Their inert nature also means growers can quickly adjust the conditions within the foundation zone to fulfill the requirements of plants. A non-existent cation exchange capacity (CEC) prevents nutrients from being changed by the growing medium or betrothed and made unavailable for plant uptake. The cubes may be quickly rinsed with water, leaching fertilizer salts out.

Rockwool cubes are available in a pair of various sizes. the tiniest ones work well for starting seeds and propagating stem and leaf cuttings; the larger cubes are employed by growers to grow more compact plants.

Grodan Pro A-OK 50/40 6/15, 2"x2" case of 1,500, comm

Do’s and Don’ts of using Rockwool Cubes

One of the drawbacks to using rockwool cubes is that the special care and consideration that must be taken when working with them. While they’re a beneficial resource for hydroponics growing systems, they are doing have some important drawbacks that require to be addressed.

DO take the time to properly prepare rockwool cubes before starting seeds or trying to root cuttings. Their natural pH is just too high for optimum plant growth and can create problems and instability within the hydroponics system if left at that alkalinity.

DO wear protective gear to stay safe when handling rockwool material. The fibers are irritating to the skin, lungs, and eyes so it’s imperative to safeguard yourself. At the minimum, wear a dust mask to forestall inhaling fibers into your lungs. It’s also recommended to wear eye protection and long sleeves if there’s an opportunity for prolonged contact along with your skin.

DO sterilize the feeding solution before running it back through the rockwool cubes. although it’s a manmade, inert material, it can still be vulnerable to algae and bacterial growth which will contaminate the hydroponics system if the feed solution is recirculated without being treated properly.

DO get rid of the materials properly after you’re done using the cubes. Unlike other growing mediums, rockwool isn’t composed of natural materials so it’ll not break down over time. If it reaches the landfill it’ll be there indefinitely. rather than throwing them away, cut the pieces and work them into your garden or potting soil to assist increase their water retention.

DO heat treat the rockwool cubes if you’re visiting reuse them for a successive season, or perhaps numerous seasons. this could be done by steaming them or pouring boiling quandary through them to exterminate any bacteria or fungus that will be residing with the cube’s fibers. Some websites recommend using chemical treatments to sterilize rockwool cubes to use again but this may be dangerous unless you’re absolutely sure you have got rinsed all of the sanitizing chemicals out of the fibers.

DON’T squeeze the cubes once they are wet. If you would like to get rid of a number of the water from them after preparing them in an exceedingly pH-controlled solution it’s best to shake them gently. Rockwool cubes are known for his or her internal structure that provides them such great water holding capacity and oxygen movement; squeezing them compacts the structure and hinders the advantages they’re so well-known for.

DON’T forget rockwool is totally inert and might not provide any nutritional value to the plants growing within the cubes. Everything the plant needs to come from the nutrient solution supplied to them.

Grodan Pro A-OK 36/40 6/15, 1.5"x1.5", case of 2,940, comm

How to Prepare Rockwool

Before using your rockwool in an exceeding hydroponics system it’s important to arrange it to be used. Unlike other pH-neutral hydroponic growing media like Hydroton, and Coco Coir, Rockwool contains a naturally high pH, typically around 8.0, due to the way it’s manufactured. During the method there’s an abundance of lime that’s deposited on the fibers; lime naturally neutralizes acidity, raising the pH.

A pH of 8.0 isn’t optimum for growing plants so it has to be adjusted to the tier that’s better suited to growth. the next pH will make many plant essential nutrients unavailable for plant uptake, causing deficiency symptoms. Most plants choose to grow in slightly acidic conditions and can benefit if the pH of rockwool cubes is brought all the way down to a more acidic level.

There are other ways to arrange rockwool to be used, none of which are difficult, but they’ll be time-consuming. thanks to this you’ll have to account for a pair of days to prep rockwool before having the ability to use it.

The first step in preparing rockwool cubes is to soak them in acidic water to lower the pH. The acidic water will dissolve the lime that’s formed on the fibers during the manufacturing process and therefore the pH will drop to a higher level.

It is best to use H2O thanks to its purity but water can add a pinch if it’s the sole thing available. Adjust the pH slowly until it reaches the required 5.5; it’s critical the pH doesn’t drop below 5.0 since it’ll start to damage the rockwool fibers when it’s too acidic.

Then submerge the rockwool cubes within the water and permit them to soak for up to 24 hours. once they have finished soaking, remove them from the water and punctiliously add them to the hydroponics system and permit the system to run with no plants until the pH of the system stays between 5.5 and 6.0 — this suggests the cubes are stable and may be used.

What are the Uses of Rockwool Cubes

Rockwool cubes hold an amazing amount of water for his or her size, which provides a buffer against power outages that make close-up pumps or timers. on average they also hold a minimum of 18% oxygen between the fibers providing an amazing amount of oxygen to the foundation zone, still making it incredibly difficult to overwater the plants.

Growers primarily use rockwool cubes as growing media for 2 main purposes in their hydroponics systems: germinating seeds and propagating new cuttings. Typically the 1.5” cubes are used for starting seeds or propagating cuttings. a number of the larger cubes (up to 4”) are used as a growing medium for compact plants moreover, but on a way smaller scale.

Germinating Seeds

Starting seeds can sometimes be a stressful adventure. It’s a continuing balance between keeping them wet enough to push germination without having them so wet they dampen off and die. Rockwool cubes are popular for germinating seeds thanks to their excellent moisture retention — they’re great at helping to stay seeds or seedlings from drying out but don’t allow them to sit in an exceedingly waterlogged environment.

Moisture is that critically consider seed germination. Water enters the seed through the episperm or tiny opening called a micropyle. The presence of water will activate the enzymatic reactions within the seed that begin germination.

Cloning New Plants

Propagating new plants is that the process of taking an existing natural object (usually a leaf or stem cutting) and growing it into an entirely new plant. This method ends up in the same dead ringer for the initial and is cheaper than purchasing seeds and ranging from scratch.

Maintaining high humidity around the cutting is critical for successful propagation. Plants have to keep from drying out; without enough moisture, the plant will get in self-defense mode and can stop trying to develop new roots.

Growing new plants through propagation techniques has to happen in a very sterile environment, free from bacteria or fungus. Rockwool cubes are completely inert due to the heating process they undergo during manufacturing. This ensures they’re sterile and freed from any harmful microorganisms that would hinder propagation.

Step by Step Instructions Using Rockwool for Seed Plantings and Propagating Cutting

  1. Prepare the rockwool cubes to be used, ensuring to soak them in pH adjusted water to bring their pH down between 5.5 and 6.5.
  2. To Plant Seeds:
    1. Insert 2 seeds within the hole on the highest of the rockwool cube. Use a toothpick or other similar object to press the seeds all the way down to the underside of the outlet.
    2. Pinch the outlet closed.
    3. Place the cubes during a nursery tray and canopy with a humidity dome to lock in moisture.
    4. Maintain at 70 – 80°.
    5. Keep rockwool cubes moist by watering sparingly every few days or misting with a twig bottle after they start to dry out.
    6. Remove from humidity dome and place under lights as soon as seeds sprout.
    7. Cut the tops off the seed in each cube (if you planted 2 per cube) that isn’t the strongest or tallest. don’t pull them out because it may dislodge the healthier plantlet at the identical time.
    8. Transplant when plantlets reach 2-3” tall.
  3. To Propagate Cuttings
    1. Water the stock plant well the night before beginning the propagation process.
    2. Remove a 3-4” leaf stem cutting from the most stem of the plant, cutting it off as near the most stem as possible without damaging the node.
    3. Dip cut end in rooting hormone.
    4. Plant the cutting within the rockwool cube ensuring it doesn’t extend the underside of the cube.
    5. Fill a nursery tray partway full with perlite or vermiculite.
    6. Set rockwool cubes on top of growing media.
    7. Cover nursery tray with a humidity dome to lock in moisture.
    8. Maintain near 80°.
    9. Crack humidity dome when roots begin to emerge, gradually increasing the day after.
    10. Remove the humidity dome a pair of days after roots first appear.
    11. Transplant when roots begin to reach out the underside of the cubes.


Rockwool cubes are an imperative product within the hydroponics growing industry. Naturally occuring basaltic rock and chalk are melted down at really, really high temperatures in a very molten lava. This lava is then put into a spinning chamber to form long fibers that are later formed into blocks or cubes for simple handling. Rockwool cubes are popular because they keep moisture and oxygen well and that they never impede the event of roots. With a range of sizes and shapes available, they’re adaptable to almost any grower’s setup.

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