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Cannabis Cloning: A How to Guide

Written by @redlegcultivator

Cloning is a tool that every gardener should learn.

It allows for the preservation of a particular genetic profile without interbreeding and producing seeds with varying genetic profiles. Cloning can save you time versus seeds. Clones will grow faster than seeds once past the initial rooting phase.

Don’t get me wrong; every clone had to come from a seed. Seeds are the basis of life. One also knows, if they’ve tried, finding the perfect balance of genetic expressions in a plant can be a challenging and time-consuming process. Once you find it, you want to keep it. That’s where cloning comes in.

What is Cannabis Cloning?

Cloning is the process of preserving a genetic profile through a direct copy of the plant. We aren’t cloning on the cellular level like an animal. We are cloning by taking a cutting from a donor or mother plant and then rooting that cutting into its own viable plant. There are two main methods to do this. One is the method I will lay out; the other is cloning using agar and test tubes.

I will not go into the test tube method step by step simply because I’ve never used it. I will tell you that is my desired end state; to clone in tubes using agar. It is more efficient at saving space by not having to devote as much square footage to cloning or increasing your capacity to make clones in the space you already have.

A whole cutting is not needed either, just a small piece of plant tissue. That increases the number of potential clones per donor plant. The real bonus with this method is it allows a grower to reset the genetic back to its original profile. Clones can degrade in potency as the generations further, and disease can set in, making the plant not a viable option for production. Cloning using agar and test tubes fixes both of those issues. That’s an excellent choice for a commercial grower whose customer loyalty and one’s reputation depend on the same quality from the same strain time after time.

Cloning by taking whole cuts can be done using numerous methods. Some people take cuts and stick them straight in soil. Others take cuts and put them in water, either directly in a cup or in an expensive hydroponic cloning machine with a pump and spray nozzles. Every one of those methods will work. Some work better than others. I use the following:

Equipment Needed to Clone Cannabis

  • 10”x20” plant tray usually comes in black or white plastic. Get the ones WITHOUT holes.

  • T50 insert – an insert that sits in the 10” x 20” with square holes for the Rockwool to sit, holds 50 cubes.

  • 7” humidity dome – Clear Plastic Dome that fits securely over the plant tray and inserts. Has vents at the top for air circulation. Maintains humidity.

  • Grodan 1.5” Rockwool cubes – They come in slabs, wrapped in paper or bags. I prefer the slabs. MOISTEN them with filtered water or a weak pH nutrient solution. I know the instructions say to soak them, but if you do not shake out most of the excess, you will run into clone loss from the media being too wet. Roots need air just as much as they need water; some say more so.

  • Seedling Heat mat – Clones root well with a temperature between 75 degrees F, and 82 degrees F. the seedling mat will help maintain that temperature to the constant sweet zone. I have one that you can set the temperature and the buffer zone and will turn on and off when needed.

  • Gardening scalpel, sharp and clean – a tool to prepare the cuttings for rooting.

  • Gardening scissors, sharp and clean – a tool for cutting clones and general pruning.

  • Rooting hormone – Powdered or gel. I prefer Clonex gel. I have gotten similar results with Cyco Cyclone gel.

  • Clonex Solution – a great micronutrient-rich solution with just enough NPK to get things started. I use it to apply to the rooting cubes and in the 10”x20” tray after rooting.

  • 10 mL pipette – I use these to aid in applying the rooting gel. The gel is expensive, and overuse is a common mistake leading to clone failure and unnecessary costs. LESS IS MORE here. I apply a thin line and work the gel around the cutting with the pipette—pictures to follow.

  • 300-400 mL of water– for the clone tray under the T50 insert.

Cutting Cannabis for Cloning

Now we get down to business. Cloning is all about the preservation of a particular set of genetic expressions. Once you find them, you want to keep them for as long as possible. You need to make sure you take very good care of your donor plants. Stress can alter genetics, degrading potency and viability. 

When you have selected the donor plant, there are several things you can do beforehand to set yourself up for success. First, make sure you take clones the day after your Integrated Pest Management (IPM) application. My IPM S.O.P. dictates that Mondays are my spray days for donor plants. Thus, Tuesdays are my clone days. Doing this ensures the clones have been treated for bugs and mould the day before cutting, allowing for that application to carry the clone through to rooting and transplant before another IPM application is needed.

Second, make sure your donor plant is healthy. I know I mentioned this earlier, but it cannot be overstated. Health is one of the keys to success. It makes the whole process that much easier. I know we’ve probably all or will someday take clones off of a struggling plant because you want to save that strain. Make that the exception instead of the rule.

Third, take cuts from the bottom of the plant and work up and out. Some natural hormones and auxins promote rooting. These are found throughout the plant but are more prevalent closer to the roots. Taking cuttings from those areas will aid in faster rooting, and fewer cuttings lost to waste.

Cloning Cannabis Step by Step

Step 1

Prepare a cup or measuring cup with filtered water and the appropriate amount of Clonex Solution. Make sure it is large enough to hold all of the cuttings you want to take. Using clean and sharp scissors, take cuttings from your donor plant. Make sure you are cutting from the bottom and as close to the stem as possible.

cannabis cloning

They should have three to four nodes on them.

Cut the remaining lower nodes off if needed. Strip off all large fan leaves not associated with your nodes as well. Clip all of the remaining leaves at the tips.

Cutting leaf tips reduces transpiration and induces rooting. Make clean, sharp cuts for the health of your plants. Place the cuts in your cup with the prepared Clonex Solution stem down.

cannabis cloning

Continue taking cuts like this until you are finished and ready to move on to step two.

Step 2

Take a cutting from your cup and measure the clone against the blades of your scissors. That is the length you want your clone.

cannabis cloning

Cut the excess off at a 45-degree angle.

Doing this allows you to make clones uniform in height. This helps ensure even canopy height later on in the growing process and helps the clones root faster. Smaller clones root faster in my experience.

Step 3

Hold the clone in your hand bottom up. In your opposite hand, use your scalpel to scrape and shred the end of the clone until it looks like a chewed stick.

Do not cut all the way through the stem. You need it to be still rigid enough to push into the cube. Scrape just the outside layers of tissue. Cutting the stem at a 45-degree angle allows the rooting hormone to contact more surface area of the plant’s cells, thus increasing rooting chances.   

Step 4

Pour a small amount of Clonex into a small shot glass. Replace the cap. Never stick anything into a bottle like Clonex that makes contact with plants. Doing so will contaminate the entire bottle. Use the pipette to suck up some Clonex. Using the pipette, apply a thin line to the area you just prepared with the scalpel.

Use the pipette to spread the Clonex gel all over the prepared area.

This allows you not over to apply or waste Clonex. Using too much can kill the cutting before it can root, wasting resources. LESS IS MORE.   

Step 5

Take your clone and place it in the prepared hole in the rooting cube.

cannabis cloning

Push it until the prepared area you want to root is entirely in the cube.

cannabis cloning

Do not push the bottom out of the cube. Place the cube in your tray, insert and repeat the process until complete.

Cover all of your cuttings with the humidity dome and place the entire tray on the seedling mat. Set this under a cool blue 25–50-watt T-5 bulb. A stronger light is not preferred. The cool blue spectrum also aids in rooting. Plug in the seedling mat and set the temperature to 77 degrees with a +/- 2.5-degree variance. Put 300 to 400 mL of water in the bottom of the 10”x20” tray. Ensure that the bottom of the inserts holding your clones does not touch the water.

The seed mat will heat the water in the tray and form a good warm, humid environment, preventing the need for spraying clones for humidity control. Leave it be for three days.

On the fourth day, open the dome to exchange the air by just pushing the dome’s edge onto the tray, so it sits unevenly. Open the domes’ air vents to make a flow of air go into the dome.

Keep the water in the tray from evaporating completely. Continue this for approximately 14 days or until all cubes have roots growing down into the water in the tray under the inserts. Your clones are now ready for transplant.

Sapere Aude!

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