How to Clone Cannabis With Rockwool?

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Added 30 July 2023

Cloning is an age-old process of replicating the best genotype of a cannabis plant that makes it your favorite. As the name suggests, cloning allows you to create replicas of the mother plant, and it is the go-to choice for many cannabis growers. It’s efficient, easy, and promising. 

Growers have been using various methods to clone cannabis, including various growing mediums. One such growing medium is rockwool, which is gaining a lot of popularity in recent years. Should you and can you use rockwool to clone cannabis, and how do you do that? Learn all about cloning cannabis with rockwool in this article.

What is Rockwool?

What is Rockwool?

Rockwool has come to be known as one of the best-growing mediums for cannabis plants, especially in a hydroponic setup. This material is made from spinning molten volcanic rock, which is why it strongly resembles fiberglass. 

What makes rockwool the ideal choice for cannabis growers is that it retains water and air, which is ideal for germinating seeds and rooting clone cuttings. Additionally, rockwool has various benefits, such as the following:

1. Cheap and easily available

Rockwool is available in most local nursery stores. Of course, if you walk into a hydroponics store, you’ll find various options. If you don’t have the time, you can simply place an order online and prepare them for clones. Also, it’s pretty cheap, so you don’t have to worry about investing too much. 

2. Exceptional Water Retention and Aeration

The fibers in rockwool enable it to retain more water This is due to the capillary action that attracts water from the base and lets the entire substrate remain sufficiently moist. Despite having excellent water retention, it still drains well and fast 

In addition, the little pores allow for more oxygen exchange and provide more aeration. Since clones perform well if they are moist at all times with enough oxygen in the roots, rockwool is one of the best choices to clone cannabis. Also, rockwool provides a sterile environment for the clones and prevents them from getting affected by diseases and pathogens. 

3. Easy to Use

Rockwool cubes come pre-scored with holes that make it easy and practical not just to clone cannabis plants but others as well. The holes will also provide stability and prevent the clones from toppling over during the cloning process. If you’re a beginner to cloning cannabis, you can’t go wrong with rockwool as the process is pretty straightforward. 

4. Quick Root Development

One advantage of using rockwool to clone cannabis is that it helps the clones take root pretty quickly. This is because rockwool allows the moisture levels to be consistent, without becoming too dry or overly wet. Clones take root fast when there’s a balance, which means that the medium shouldn’t be dripping wet or too dry. 

Thanks to the development of quick roots, there are fewer chances of transplant shock, which is a common problem among beginners. When it's time to transplant the rooted clones into their permanent growing containers, you can place the rockwool cube directly in the new medium without disturbing the delicate root system. This minimal disruption to the roots helps reduce transplant shock, leading to a smoother transition for the young plants as they continue to grow.

5. Compatibility with Hydroponic Systems

Hydroponic growers prefer mostly rockwool as the best growing medium to cultivate cannabis because it’s perfect for hydroponics. Hydroponics relies on delivering precise nutrients to the roots and since rockwool achieves just that, you will be growing cannabis plants in no time. 

When it comes to cloning cannabis with rockwool, you’d probably use rockwool cubes. These cubes are different from germination cubes as they are larger, wrapped in plastic on all sides except the top, and have a small hole in the center for the clone cutting. Ideally, rockwool cubes are what you should use unless you’re cloning a large batch, where it would make more sense to get yourself rockwool slabs — it’s cheaper. 

How to Clone Cannabis with Rockwool Cubes?

How to Clone Cannabis with Rockwool Cubes?

Now that you know what rockwool is, let’s dive into how you can use them to clone your favorite cannabis plant. Follow these steps.

1. Gather the Supplies

The first step is to gather the tools and products you’d need for rooting your clone cutting. Here is a list of everything you need for this project:

  • Rockwool cubes 
  • Clone cuttings of around 4 to 6 inches 
  • A rooting hormone or gel of your choice — even honey works
  • Diluted nutrient solution 
  • A sharp pruning scissor or knife 
  • A clear plastic cover 
  • A propagation container to hold rooting clone cuttings

2. Pre-treat the Rockwool Cubes

Rockwool, as good as it is, must be treated before use because it has a relatively high pH and it’s inert. So, you can treat your rockwool cubes by soaking them in a diluted nutrient solution with a pH of around 5.2 for the night. The next morning, soak it once in a pH solution of around 6.0 to stabilize the alkalinity of the cubes. 

Many growers recommend squeezing the rockwool cubes to remove excess water but do not do this. It’s a mistake that will ruin your rockwool cubes. When you squeeze them, the fine fibers are destroyed and your cube will lose its ability to hold water and air and it will fail to drain properly. 

3. Prepare Your Rooting Hormone

While the rooting cubes are soaked, you can start prepping the rooting hormone of your choice. These hormones come in various forms, including power, gel, and liquid. Depending on your preferences, you can get the one that works best for you, but whichever you choose, ensure it is of high quality from a reputable brand. 

Follow the manufacturer’s recommendations for preparing them. Skip this step if you have a rooting hormone that doesn’t require any prep. For example, molasses or honey don’t need any preparation. 

4. Take Your Cuttings from the Mother Plant

The next step is to take cuttings from the mother cannabis plant. Ideally, your cuttings should be about 4 to 6 inches in length. To do this, make a diagonal cut on the branch just below the lowest node. Ensure the cut is clean and quick, so the rooting hormone can be easily applied to the cut. 

5. Insert the Cutting into Cube 

Next, dip your clone cutting into the rooting hormone for a minute or two, as per the rooting hormone’s recommended procedure. Then, gently insert the clone cutting into the hole in the cubes. Often, the hole on the cube will be smaller than the stem’s diameter, in which case, you can spread the hole out with a tweezer. 

When inserting the clone cutting, do so slowly and only insert the cutting about 1 ⁄ 2 inch into the cube; any more and the cutting may tip over and any less and the roots won’t have enough space to expand. 

Once the cutting is inserted into the cube, gently close any gaps between the stem and the cube — you can use the same tweezers to close the gap, but be very gentle during this process. 

6. Rehydrate the Rockwool Cube

The clone cutting is almost ready for rooting, but before that, you need to rehydrate the rockwool cube to ensure it has enough nutrients to sustain the clone. For this, rehydrate the cube by irrigating it with a pH-balanced nutrient solution and allowing excess water to drain out. 

7. Move the Clone Cutting to the Rooting Space 

It’s time for propagation. So, move your clone cuttings to a propagation container with a temperature of around 80°F to 85°F (27°C to 29°C). Also, don’t forget to set up a grow light over the cutting on a 24/0 light cycle. Generally, a fluorescent grow light of 40 watts works best. 

The container should also be humid for the roots to develop properly. So, we recommend sealing the container with plastic cling wrap. If the ambient environment is too dry, you can even sprinkle some water on the container’s insides to increase the internal humidity before sealing it. 

Once you have placed the cuttings, avoid moving the container or the cubes, even if it’s just to check the rooting progress. Keep the container as is for at least eight days, but keep checking for mold or fungus in the humid container. 

During the rooting process, you must keep spraying the cutting with nutrient water, but once you notice the roots developing on the cube, you can start watering the cube directly. But visible roots are not a sign of your clone cutting being ready for transplanting. You must be a little patient. 

8. Transplant the Clone Cuttings 

When should you transplant the clone cuttings? Generally, wait for a day after the roots start showing themselves. Then, open the container to let the humidity out and the clones to acclimatize to the new conditions. For the first hour, check the clones for any signs of wilting; if they start wilting, spray them with the nutrient solution and reseal the container for one more day. 

If the clone cuttings don’t wilt even after being exposed to the external environment for 5 hours, you can start transplanting them. Depending on your cannabis setup, you can gently pick up the rockwool cube with the cutting in it and move it to the final growing space. 

For a soil-based cannabis plant, you want to dig a hole big enough for the rockwool cube to fit in, place the rockwool cube in the soil, and cover it with a thin layer of soil. For a hydroponic setup, you can place the rockwool cube in the growing medium or in the tray. Don’t forget to irrigate the clone cuttings after transplanting. 

That’s it. You’ve successfully cloned your favorite cannabis plant with rockwool cubes. Henceforth, keep taking care of the plant and watch it flourish and produce big, bushy nugs. 

Summary: How to Clone Cannabis With Rockwool?

If you are a green thumb cannabis grower who wants to clone cannabis plants, now is the time to start. And what better way to clone cannabis than rockwool? Hopefully, this article will work as your guidebook to clone cannabis with rockwool. 

Remember, rockwool is a terrific growing medium but it has a little attitude. It has a high pH, so you must prepare it before use by ensuring it is pH balanced and loaded with nutrients. Then, dip your fresh clone cuttings in a rooting hormone and place it in the rockwool cubes. 

Rehydrate the cubes, place them in a propagation container, and seal the container with cling foil or something similar that lets the light in but holds the moisture within. After some days, you’ll start noticing the roots. Wait for one more day, check if your clones are ready for transplanting (they shouldn’t start wilting), and transplant them into the final container or growing medium of your choice. 

Cloning cannabis is a rewarding exercise, and with the help of rockwool, the entire process becomes easy and manageable even for a new grower. So, what are you waiting for? Get start today with cloning cannabis with rockwool cubes. 


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