How is Growing Marijuana in Rockwool Done?

If you are looking for the best way of growing marijuana while taking control of the compounds and elements that are consumed by the plants through their root system, Rockwool would make a credible option. But how do you do it?

Rockwool is an excellent medium for marijuana cultivation. Nourishing your best choice of strain to a whole life cycle is definitely possible with Rockwool. Regardless of your level as a grower, growing marijuana in Rockwool will lead you to a sooner abundant yield.

Things to Do When Growing Marijuana in Rockwool

Growing marijuana in Rockwool is very manageable. These are the steps involved when getting involved in this venture:

1. Establish your Cultivation

The first thing you need to do is to prepare your Rockwool before employing it for your marijuana growing. When untreated, its pH level is at 7.0 which is very alkaline for robust marijuana development, since there are no instinctively occurring intermediaries similar to the soil. If your substrate has excessive alkaline, your plant will have insufficient nutrient uptake, particularly magnesium and calcium. 

Saturate the Rockwool for 24 complete hours in a nutrient solution rectified to a pH of 4.5 and EC that ranges between 0.4 to 0.5. This length of values will ensure the young plants embark on a firm outset as it encounters no deficiencies in the nutrient.

You can determine if the Rockwool is already set at the right pH by deluging a 5.5 pH nutrient solution and examine the overflown water using a pH meter. If you get still get a reading of 5.5, it means that the Rockwool is already set for use. However, if you still a very high reading, re-saturate it for several hours and do the reading again.

2. Germinate

The good thing about Rockwool when growing marijuana is that it does not need any special germination methods. You can simply use a paper towel. Place the seeds within the two layers of wet paper towel on a plate and top it with another plate. Place it in a dark and warm place until you notice the seeds to break up and the taproot crops up.

Slowly imbed the germinated seed in an established Rockwool cube and put underneath propagation lights to achieve early vegetation. The well-nourished sprout will immediately occur. The cotyledons will cast off the seed husk and widen. Soon, they will be trailed with an actual set of leaves.

The moment the young plants are placed in their little Rockwool cubes; you can then transfer them to the succeeding size of the appropriately established cube. Making sure that you will not cause any injury to the visible roots, slowly squeeze the small-size cube into the bigger one to guarantee a good fit having no air pockets. 

Plants are then set for an introduction to a complete artificial light in a certain grow space.

3. Clone and Root Cuttings

The method of cutting the roots and rooting in the Rockwool is just similar to peat moss, coir, or jiffies. Simply put the cuttings on well-established Rockwool cubes. The cubes must be damp, but not to the extent of being wet to prevent the stem from getting rotten and slow to strike.

Place the cuttings in an environment with high humidity and lightly mist routinely with water. The moment cuttings strike, reduce the humidity level for several days, then take off the cover to compact them off before transferring. 

4. Grow in Rockwool

Rockwool is best for an automatic irrigation system. The matter is extremely permeable and smoothly gives away nutrient solutions in the entire root system before immersing at the lowest part. This moisture declivity makes Rockwool an ideal element for hydroponics.

It is also acceptable to hand-water, however, you should be ready to exert more effort since you will have to conduct numerous visits to the growing area every day. Also, you should be very cautious as you do not want to overdo it, too.

Plants settle in a hollow film of nutrient solution, ideally with a depth of 2 to 3 mm. Rockwool must be at average impregnation levels in the very curtailed layers, while drier in the top layers.

The lower roots nourish themselves from the layer of nutrient solution. The upper roots, on the other hand, are introduced to moist air along with the available oxygen they can have for hearty development. Remember that Rockwool is not meant to be soggy just like a sponge since this is tantamount to drowning the roots, which will wipe out the plant.

Moreover, Rockwool can be utilized in holding the marijuana plants for the Deep Water Culture system. There is a bit of salt accumulation since, in every irrigation, a new solution compels the old salts away and brings more fresh air to the medium. 

5. Vegetation and Flowering

While in the early period of vegetation, irrigate for 1 minute to administer a nutrient solution of 60 to 70 ml two times a day. Once the lights enter, then again medial through the cycle of light. 

During the flowering stage, shift to a flowering nutrient and slowly heighten the pH for more than a week from 5.5 to a range of 5.8 to 5.9. In the second week, heighten the EC to 0.8 to 0.9 and the pH level to 6.0. The watering schedule should be adjusted too, ideally 2 to 3 times a day. When lights are on, irrigate for 2 minutes. 

Relying on the kind of strain, reduce the EC on the last week of the flowering stage as low as possible. Maintain a pH level of 6.2.


Rockwool is a fundamental substrate in hydroponics marijuana growing. For those who have not tried Rockwool yet in their cultivation, now is the time that you start embracing its value and utilize its advantages. By growing marijuana in Rockwool, you will likely have excellent end products. This is as long as you do the steps the right way.

The guides above are detailed and simple. Surely, you will have to exert patience and dedication. But if you have a strong desire of achieving quality products during the harvest period, then this is worth trying!

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