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growing weed from seed in rockwool

Growing in Rockwool

Growing in rockwool is a sort of step towards hydroponic growing, as they’re both inert substrates meaning that there’s no organic material decomposing. This means that when you water this plant you’re going to need to fertilize it with the necessary nutrients so that your plant can grow vigorously and strong.

You can find various formats of rockwool to grow in. First, there are little 5x5x5 cubes used for germinating or clones, although it’s recommended to grow clones on a tray with 77 or 150 cavities, as it’s much more organized, or you can grow them in rockwool slabs as well. You can get larger cubes, 10x10x6.5cm, perfect for growing in both rockwool slabs and with the Gi Grow Wheel. Rockwool slabs are bags that measure 100 x 15 x 7,5 that contain rockwool. The biggest advantage that rockwool has over coco coir or soil is that it is an extremely airy substrate with allows you to grow abundant harvests without having to transplant and possibly damage the roots.

So, when you first begin growing in rockwool you might be a bit confused on how things work. The first thing you’ll need to do once you have the rockwool is let it soak in water, preferably with a pH of around 4.5-5. This pH level is important because it lowers the original pH from 7 to 6, allowing the plants to absorb all of the nutrients right from the start.

Once the pH is under control, you’ll need to move on to germination, cloning or growing. We usually recommend germinating using a plastic container and some kitchen paper. Once the roots are out of their seeds, you can move them to your rockwool cubes and begin growing. It’s important to control how much you water and humidity at this point. We don’t recommend watering too much or having constant water, as the roots need an opportunity to take advantage of the extra space and air that rockwool provides. This will also prevent the appearance of algae on the rockwool cubes. If you want to completely avoid these algae, you’ll need to keep the substrate completely out of the light like in this picture.

If you’re cloning, once you have your clone ready with rooting hormones, place it in the rockwool. The proportion of air will allow you to root over 7 to 10 days, avoiding any rot in the stem. You’ll also need to stabilize the pH in the rockwool to avoid any eventual root blockages. The irrigation will need to be controlled and automatic to make sure that the rockwool doesn’t get too dry and stress out the roots which would affect the final yield.

The biggest rockwool blocks are used with Gi grow systems; they’re placed in the racks and can easily deal with the weight of the plants. There are two versions, although the only difference is the size of the hole in the package.

These blocks can be used as an additional support for those that grow in rockwool slabs. The advantage to doing it this way is the amazing production rate, the comfort of not having to transplant your plants and the possibility of growing horizontally, vertically and in sand. Watering time would change horizontally and in sand, rising little by little to give more water each time, so as well as raising the amount of water you’ll need to increase the EC level; we recommend having an EC gauge handy for your grows. When growing vertically, you can water for as long as it needs for the water to reach the plant furthest away.

It’s important to remember that, just like with hydroponics and coco coir, it only takes a week to clean out the roots. This is due to the substrate’s low retention of salts and nutrients.

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What’s The Best Growing Medium For Cannabis?

The sexy parts of your cannabis plants may be above ground, but it’s down in the root zone where the real magic happens. By taking in nutrients, water, and oxygen, a plant’s roots provide everything it needs to grow and produce top-quality bud. The growing medium largely influences the ability of a cannabis plant’s roots to do so, so picking the right substrate is a pretty important decision.

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Soil – The Most Basic Cannabis Growing Medium

Plants have been growing naturally in soil for millions of years. It’s only logical to use this widely available material as a growing medium for cannabis. Cheap and easy to work with, the soil is probably the best choice for all novice growers. It’s also considered by many to produce the best-tasting weed.

Because soil contains many microorganisms that help regulate all aspects of the environment, much of the work is taken care of with little input required from the grower. Fluctuations in pH or other variables generally have less drastic consequences than they would in other growing mediums. So there’s more room for making mistakes.

Many commercial soils also come packed with nutrients, so there’s no need to add any extra fertiliser or plant feed. Not for t the first few weeks of the growth cycle anyway. Soil is also the most natural and environmentally friendly cannabis growing medium.

On the downside, soil can harbour pathogens and pests that could harm your plants. Additionally, the natural growth rate in soil is less than in other growing mediums. Some of which can support larger cannabis plants and greater cannabinoid yields.

Coco Coir – A Hugely Popular Cannabis Growing Medium

Coco coir is a by-product of coconut harvesting and has become extremely popular as a growing medium for cannabis. Made from discarded coconut husks, this fibrous material offers excellent water retention and aeration.

Because about a third of the fibres in coco coir repel water, air pockets are always present. Within such a structure, roots can grow and access nutrients much more easily than soil, which frees up more energy for plant and bud development. For this reason, cannabis plants grown in coco coir tend to grow faster and become larger than those cultivated in soil.

Of course, all this depends on the grower adding the right blend of nutrients into the mix. Coco coir itself is inert, which means it contains no nutrients and can’t support plants on its own. It also lacks any microorganisms found in soil, so growers are responsible for manually controlling every variable.

This is both a positive and a negative, as it allows for more control over the root zone environment and provides little leeway for making mistakes. Growers must continually monitor the pH level to ensure it remains within the optimum range and supplies the right blend of nutrients at each stage of the cannabis growth cycle.

Coco coir has excellent drainage and oxygenation and is a popular growing medium for cannabis.


Rockwool is the brand name for a type of mineral wool that is made from volcanic rock. Like coco coir, it has excellent drainage and aeration and has become a popular growing medium for cannabis.

Unlike coco coir, however, Rockwool is neither organic nor biodegradable. Its production involves intense industrial processes that are not environmentally sustainable. On the flip side, the fact that it contains no organic matter makes Rockwool impervious to harmful bacteria and fungi, drastically reducing the potential for plants to become diseased.

Growers must supply the correct water and nutrients while also maintaining the proper pH level throughout the growth cycle. If this is achieved, Rockwool can support rapid root growth, resulting in large plants with excellent yields.


Not strictly a cannabis growing medium, hydroponics is an umbrella term for various techniques that involve growing weed without soil. Hydroponic systems vary significantly in nature, yet all involve delivering nutrient-rich solutions directly to the roots of a plant at set intervals.

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Some hydroponic set-ups use growing mediums like coco coir, Rockwool, or clay pebbles to anchor plants’ roots. In contrast, others simply suspend plants above a reservoir with their roots dangling down into the water. By eliminating the need for roots to search through soil for nutrients, these methods allow plants to direct more energy towards producing stems, leaves, and flowers.

The absence of soil also reduces the chance of disease and minimises the potential for nutrient ‘lockup,’ which occurs when nutrients become fixed in the soil and remain unavailable to plants. As a result of all these things, hydroponic systems allow growers to boost their yields considerably.

The trade-off is that hydroponics can be costly and complex, and therefore isn’t necessarily suitable for beginners. Plants grown this way can sometimes have a slightly unnatural flavour, which is why many people choose a more conventional growing medium for their cannabis.

Cannabis Growing Medium Mixes

If you can’t settle on a suitable growing medium, you can always mix and match. Adding coco coir to soil, for example, improves its structure and increases water retention and oxygenation.

Perlite, meanwhile, is a lightweight material made from volcanic glass, which attracts oxygen to its surface. Many cultivators add this to their cannabis growing medium to enhance aeration and minimise roots’ energy when seeking out nutrients.

Finally, some growers choose to add peat moss to their soil, though this is somewhat controversial. The process by which peat moss is extracted from peat bogs produces considerable carbon emissions and destroys local ecosystems, so some countries are considering banning it.

However, when added to a cannabis growing medium, peat moss massively increases water retention and introduces beneficial microbes that help make nutrients more available to plants.

Overall, it’s impossible to say which growing medium is the best for growing cannabis. Ultimately, this will depend on each growers’ needs, expertise and budget. With so many options, though, the choice is yours.

How to grow marijuana with aeroponics

Aeroponics is a method of growing marijuana plants in which roots are suspended in air inside of a chamber and sprayed with water. Aeroponics is commonly used to start cannabis clones in order to give them a healthy root system before being potted into soil or another growing medium, but can also be used to grow full plants.

This growing method was first created in the first half of the 20th century as a way to study a plant’s root system. Initially created only for research, aeroponics has since become a popular way to cultivate cannabis clones and plants.

How do aeroponic growing systems for weed work?

Aeroponic growing systems use a water-tight chamber that has multiple misters in it. Also known as “cloner,” you can buy these ready-made or build your own.

When cloning, once clones are taken off a mother plant, a foam collar is put around each clone and then placed in the cloner. Once all clones are in the cloner, the chamber is filled with water and nutrients are added.

To grow full plants, a planter bed is needed. To start, a seedling grown in a medium, such as a rockwool cube, needs to be placed in a net pot and a collar is then placed around the base of the stalk. This collar helps prevent mist from evaporating or molding the stalk and also protects the roots from infection and damage.

As with clones, water and nutrients in the chamber are pumped through to misters that blanket the roots of the plants. Excess moisture collects in the chamber and drains back into the reservoir to be recycled for later use.

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Advantages and disadvantages of growing weed aeroponically

Advantages of aeroponic systems for weed

Aeroponic systems are known for the quality product they produce. Applying nutrients directly to roots allows for development of large, healthy buds. Buds grown with aeroponics are known to blossom with ripe trichomes and in high yields, making for a lucrative and desirable end product.

In an aeroponics setup, cannabis plant roots are in full contact with oxygen at all times, helping roots thrive. Also, when nutrients are dissolved in water and directly applied, they will be more readily available for the plant to uptake.

An aeroponic setup will also save space as plants can be placed closer together because they don’t have to fight for soil. The lack of soil also helps prevent pests.

Aeroponics also uses much less water compared to regular soil growing as water not taken in by plants is recycled.

Disadvantages of aeroponic systems for weed

Aeroponics may take some time, effort, and skill to figure out, and may be challenging at first if you’ve never grown weed before.

Aeroponic systems usually work on a timer, misting roots at set intervals throughout the day. Because of this, power outages, broken pumps, clogged nozzles, and empty reservoirs can all derail your growing.

Roots without moisture will quickly start dying, so you need to have systems in place to alert you of failures, and you need to be on hand to solve problems when they arise. Aeroponics requires close attention to detail and can be labor-intensive and time-consuming.

Although it can cut down on pests, weed plants grown aeroponically will be more prone to root rot and mold. Sometimes, aeroponic weed plants lack the complex flavors that can be found by growing in soil.

How to grow aeroponic weed step-by-step

To start growing weed with aeroponics, you’ll need to set up an aeroponic machine, also called a cloner. You can make your own or easily purchase one—check out our Buyer’s guide on cannabis cloning equipment to see various options at different price points.


Clones need to get vegetative light, so 18 hours a day. Make sure to get a light that isn’t too hot, and set it up 1-2′ above the clones. T5s work great for clones.

To set up the aeroponic machine:

  • Fill up the chamber with water and nutrients
  • Set up the pump
  • Set up the misters

After taking a clone of a plant, you’ll need to put a foam collar around it—which holds the clone in place—and put it in the machine. Once all clones are in the machine, turn it on, and it will start misting the bottoms of your clones.

You can get a timer for the aeroponic machine, which will mist stems at intervals. You’ll have to experiment with it to get the best results.


You can start seeds in an aeroponic system using a net pot, which is a basket with holes in it that is filled with clay pellets or another grow medium.

Also, when clones have rooted out, you can transplant them into a net pot and finish out the rest of the plant in the aeroponic system. Once in a net pot, grow the plant as you normally would.

With aeroponics, you’ll need to keep an eye on:

  • Water level in the tank—plants will soak up more water as they get bigger
  • Amount of nutrients (change according to growth cycle)
  • Length of time misters are on
  • Light height—increase as plants get bigger
  • Clogging—check pump and misters regularly to make sure water is circulating through the system and getting to the plants

Aeroponics is a great way to grow high-quality weed. It’s a little less complicated then hydroponics, and once you have the aeroponics machine setup, it’s just a matter of checking to make sure it’s still running properly.