This article first appeared in the Tech Issue of Fat Nugs Magazine, published December 2024
Hey there, home growers! Welcome back to my basement. This issue is a challenge for me. See, I am a tech geek to the core. If I were to start writing about the technology available to you as a home grower, and the gear that I’ve demoed in my garden, I could fill this whole edition!
But I am going to set all of that aside. Why? Well, because we have some unfinished business.
In the last edition, I got us neck deep into our own little pheno hunt and left you hanging! It was just too big a subject to tackle in one issue. If you’re asking, “What’s a pheno hunt?” do yourself a favor and hit pause on this article while you log into FMN and read part one in the Flower Edition.
Everyone ready? Great!
The Miracle of Cloning Cannabis: Nature’s Technology
From a cultivator’s perspective, we’re going to dig into something that is rather low-tech. (It’s also something that won’t set you back an arm and a leg.) But if we were to frame it as “nature’s technology,” then it really is quite amazing. That miracle is cloning.
Whether it’s tomatoes, leeks, or lettuce, we as cultivators are capable of asexually reproducing a wide variety of plants. I am currently phenotyping and cloning African daisies in my garden.
But today, we are going to focus on our favorite plant, cannabis sativa. Just understand that the process is similar for most species.
With a little precision, a mind towards cleanliness, and the right environment, we can cut a small branch from a healthy “mother” plant and begin the life cycle again, creating an entirely new plant from that branch, essentially an exact copy of that mother plant.
If you’re in the middle of a pheno hunt and you have a few female plants that you’re ready to transition into the flower cycle, now is the time to clone each of those females. You will care for and continue to vegetate those new plants while the mothers finish their flower cycle. You may even find yourself pruning those little clones because they’ve gotten too large while you wait for their mothers to finish up. I’ve even cloned a clone to start the process over while I waited!
Or, maybe you’ve already found a phenotype that you like, and you just want to grow more of it. Clone it, baby. Make a few. Make a dozen! Virtually every shoot on that mother plant could be a new plant if you want it to be.
But as part of a pheno hunt, you really only need one. You are just looking to preserve the genetics until you are able to decide whether or not it’s a keeper. You also don’t want to cut too many branches off of a plant that you are about to flower.
If done properly, cloning cannabis can have a near 100% success rate. Regardless, I always take a few cuttings of each variety to give myself a little insurance, in case I run into problems. Cloning doesn’t take much time or many resources, and it’s easy to just discard the extra clones that you don’t need.
Methods of Cloning Cannabis: Propagation vs Aeroponics
There are two methods of cloning cannabis that are available to the average home grower. One uses simple propagation trays, putting the cuttings in starter cubes that typically are made of peat or rockwool. The other method is using an aeroponic cloner. I prefer aeroponics. But today, we’re going to learn to start with cubes. It’s how I first learned to clone and it is by far the preferred method, both commercially and in home grows.
Propagating Your Clones
You will need a few items to get started cloning cannabis:
- Propagation tray with a humidity dome
- Starter cubes
- Small packet of rooting hormones
- Razor blade or scalpel
- Possibly two pH adjustment solutions (one to raise the pH and one to lower it)
Start by soaking the cubes in water. I recommend a light nutrient solution. There are solutions specifically designed for cloning, but you can use any nutrient line. I have used a traditional flowering fertilizer as they are higher in phosphorus, something the cutting will use to create new roots. The challenge with any nutrient is ensuring that it is not only the right concentration but also the right pH for cloning.
If there is any “tech” that I would recommend in this issue, it’s a pH meter and an EC meter. The pH meter will measure how acidic a solution is. The EC (or electrical conductivity) meter, ultimately measures the total amount of dissolved fertilizers in a solution, or its concentration. Too low and the plant will be malnourished. Too high, and the plant won’t be able to effectively move nutrients and water efficiently enough to meet the demands of photosynthesis. Ultimately, the plant will suffer in similar ways.
If these tools are out of your budget for now, just start with water. But if you can afford to add them to your toolbox, do it. These meters will prove invaluable in your garden.
Getting Into pH
All nutrients are absorbed optimally by the plant at a specific pH and it’s a bit different for each nutrient. If the pH of the solution is too high or too low, the plant will not be able to uptake that nutrient, which is called lockout.
A good general target for that pH is 5.8 – 6.0. At that pH, the plant will be able to uptake all of the necessary nutrients efficiently enough. For cloning, I aim for a lower pH, in the 5.5 – 5.7 range. This pH is less than optimal for nutrient uptake, but the more acidic solution will help prevent the growth of bacteria in your media, giving your cuttings a better chance of success.
The EC of the solution is not as critical, but I generally like it to read 1.2 – 1.4. Some EC meters will use this reading to calculate parts per million (or ppm) for you. The corresponding ppm would be 600-700.
After the nutrients have been added to meet that EC, check the pH. You will then use the pH adjustment solutions to adjust the pH accordingly. Use it very sparingly and add more if needed. It is usually fairly concentrated and you can overcompensate easily.
Whether you’ve soaked your cubes in nutrients or water, squeeze most of the solution out of the cube and place them in the propagation tray. If they are too wet, your clones are more likely to rot than root. I like to use a checkerboard pattern, only using every other space in order to give the cuttings room to breathe.
How to Take Your Cuts
Now it’s time to take your cuts. I prefer to take more vigorous cuttings from near the top of the plant, but if they are mothers about to go into flower, I’ll take cuts from the bottom.
I only need those cuttings to be a few inches long, but I will follow it back to where it started and prune it from the plant there. Then I will cut the small cutting to the appropriate length, making a clean 45-degree cut to the stalk, preferably right below an internode, or the point along the stalk where the plant begins new lateral growth.
After I cut it to length, I will tightly prune away any vegetation, leaving just a small cluster of leaves at the top, four to six leaves at the most. I use the scalpel very carefully to shave away about an inch of the outer epidermis of the stalk, just above the 45-degree cut I made earlier. Removing the epidermis from all sides is not necessary – I usually shave about halfway around the stem.
This is a delicate procedure, as you want to shave off the skin without cutting into the inner pith of the stem. It may take a bit of practice. If you’re having trouble, try using the dull side of the blade to rough up the epidermis, rather than shaving it.
At this point, have your rooting hormone ready and dip each cutting into the hormone solution. It doesn’t take much.
Now the cuttings are ready to be pushed an inch or two into each cube. And that’s it!
Grow Your Cannabis Clones
From here, it’s important to keep the area clean and keep the cuttings at the proper temperature and humidity. Consistency is the key to success. I would aim to keep the temperature in the mid-seventies. The proper humidity for that temperature is 65-70%. A humidity dome on your propagation tray will help you maintain that – just take it off occasionally to allow for some fresh air exchange and to help prevent the humidity from being too high. Most domes also come with vents that you can adjust to help regulate this.
Place the tray under your light. Clones will require far less light to get started than flowering or even vegetating plants, so either dim your light down to probably 10-15% of its total output or raise it at least four or five feet above the humidity dome.
And that’s it! Keep the cubes moist, but not wet. Look for fungus growing on the cubes. If so, they’re too wet. If your cuttings are wilting, the cubes are too dry. Do your best to maintain that temperature and humidity. And most of all, be patient and leave them alone.
Within about two weeks, if all goes well, you’ll see them start to vegetate again and new roots will be growing out of the cubes. At this point, they are ready to transplant. Keep the new substrate moist and slowly increase the light levels while decreasing the humidity to 55-60%.
And congratulations! That’s all there is to a pheno hunt and cloning cannabis. Other than the harvesting, drying, and curing! And sampling, of course! We’ll talk about harvesting, drying, and curing in an issue to come.
