How to Clone Cannabis Plants

How to Clone Cannabis Plants

Cloning is a technique in which you take a branch from an actively growing plant and propagate a new plant (vegetative propagation). The new “daughter” plants will be genetically identical to the “mother” plant from which they were taken. Cloning cannabis plants is a wonderful way to preserve your favorite strains and save money on seeds. However, cloning can be a difficult skill to master. It requires knowledge, care and patience to ensure the successful establishment of roots. In this article, we explain how to clone cannabis plants. We review the cannabis cloning basics, explain the equipment and supplies that you will need, and provide a step by step cloning tutorial. Our fast cloning method will get your plants rooted and ready in 7-10 days.

Cannabis Cloning Basics

Before we go through the process of cloning it is worthwhile to review the basics of climate and caring for cannabis clones. Understanding the basic principles behind the instructions that follow will allow you to get prepared for and then manage your cloning process more effectively.

Temperature: 72F - 75F (22C - 24C)

Maintaining the ideal temperature is important to allow optimal rooting for cuttings. When plants are mature and growing, it is important to control the temperature to support productive photosynthesis. However, photosynthesis in cuttings is very low. Instead, we control temperature with cuttings to promote healthy respiration. Respiration is important for all the major metabolic processes that are involved with plant development, including rooting.

If temperatures are too high, it will require the plant to transpire in an attempt to cool itself. This will deplete the cuttings of valuable water stores. If temperatures are too low, respiration rates will fall, which slows metabolic processes and delays the rooting process. Maintaining a temperature of 72 - 75F (22 – 24C) is ideal. When additional heat is required it is best applied as bottom heat, as the media is typically cooler than the ambient air. In warmer climates, however, you may not be able to apply heat with heating mats if that would cause the temperature to exceed 75F (24C).

Humidity: Over 95% Relative Humidity

Clones require a high relative humidity throughout the rooting process. The cuttings can no longer take up water effectively from the media because they do not have active root systems. As a result, the only water available to the cuttings is that which is already inside the cutting at the time of making the cut. Therefore, it is important for the cutting to maintain that water and not lose it to transpiration. Keeping the humidity high prevents transpiration and allows the plant to preserve the water for vital functions such as photosynthesis and root development. Some growers will trim the fan leaves to further reduce transpiration, however, this is not part of our regular practice. If you are able to maintain high humidity, the water losses will not be problematic and having the full leaf will allow faster development once the roots are established.

To learn more about the ideal climate conditions for cannabis, read our article: “The Best Environment for Growing Cannabis

Light: 24/0 with T-5 Florescent or Low watt LED

Rooting clones require a steady supply of low intensity light. You want to provide a long duration of light to entrain them to stay or transition into a vegetative state. We recommend a 24/0 light schedule, with the lights remaining on full time throughout the rooting process. 24/0 lighting provides more energy for faster rooting and it also allows a consistent and stable climate during the sensitive process. However, since there is no active root system, you do not want to expose cuttings to high intensity light which can exhaust the plants beyond their capacity.

One of the main causes of rooting failure is providing too much or too little light. Too much light will stimulate plants to transpire more water and possibly dehydrate the cuttings. Not enough light will slow rooting, as the primary source of energy is through photosynthesis. You want to provide just enough light to satisfy the plant’s CO2 compensation point. The compensation point is the amount of light required for a plant to make enough energy to carry out daily metabolic processes such as rooting. In technical terms, the ideal light is between 60-75umols (5000-6000 lux) but up to 100umols (8000 lux) can be fine if the conditions are optimal. In practical terms, a low wattage fluorescent or LED light works best.

To learn more about the light needs of cannabis plants, read our article: “Cannabis Light Cycle Fundamentals”. I also have several advance drafts of articles on light available in “Dr. Photon’s Corner” in our grower’s forum.

Media: Several options

There are several options for what media to use for rooting your clones. The media should have plenty of air space because roots require oxygen for respiration. For example, Rockwool Cubes always maintain at least 15% air with 80% water holding capacity and 5% fibres. This ratio of air to water allows vigorous root growth without issues of oxygen deprivation due to over hydration. These properties have made Rockwool Cubes one of the most popular choices among avid cultivators.

Although there are several choices, the media that you will end up growing with needs to be considered when choosing a cloning media. If you are growing in a water-based hydroponics like Deep Water Culture, then you should use Rockwool Cubes. Rockwool is also appropriate for coco or soil grows, but with coco and soil grows you also have the option of using peat-based media like Jiffy Pellets and Rapid Rooters.

Water:

Water is important but only enough to support roots once they begin formation. Too much water in the medium drives out oxygen and suffocates roots. Spraying the environment helps raise humidity and misting plants provides some water through osmosis in leaves.

The type of water you use is not too important. Tap or well water is acceptable, however, you should avoid hard water because it contains many solutes which can deter water from being absorbed through osmosis. You can use water filtered by reverse osmosis, but PH can be harder to adjust as there is nothing left to buffer the elements which interact with it.

The Mother Plant

Cloning starts with the mother. How you look after the mother and the type of genetics used, will influence how well and successful the rooting process will be.

The most effective strategy is to take cuttings from a mother plant that is in vegetative growth rather than flowering. However, it is also possible to take cuttings from flowering plants, which is a technique commonly known as “monster-cropping”. Clones taken from a flowering mother will take longer to root because they also must re-vegetate. We will cover the process of cloning flowering plants in a future tutorial on “monster-cropping”. In this tutorial we focus on taking clones from vegetating mother plants.

The nutritional requirements for mother plants are much different than the requirements of plants that are intended for production. Mother plants benefit from a nutrient balance with lower levels of nitrogen and potassium, which prevents excessive vegetative (leggy) growth and increases the carbon to nitrogen ratio. This nutrient balance allows plants to store more carbohydrates in leaves and stems, which aid in the development of roots during the cloning process. In contrast, if too much nitrogen is used on mother plants, the plants will grow quickly reducing these stores of carbohydrates and producing thin and weak cell walls.

Some nutrient formulas are specially made for mother plants. They offer nutrient ratios with low nitrogen and potassium and high phosphorus and calcium. This nutrient element ratio promotes high carbohydrate stores and healthy cell walls. If you are doing clones on a regular basis, we recommend Hydrodynamics two-part Mother Plant Fertilizer. For casual cloners, you can make do with one-part flowering fertilizers which have low nitrogen such as Flora Nova Bloom by general hydroponics.

Cannabis Cloning Equipment and Supplies

For Taking the Cuts

There are several items you need to gather before you take your cuts

  1. Sterile cutting tool: A razor will work, but we recommend these pruning snips
  2. Media of choice: Rockwool, Jiffy pellets, or Rapid Rooters
  3. Cloning Gel: Clonex Rooting Gel
  4. Cloning Powder: Bontone Rooting Powder
  5. pH Meter: Apera Instruments pH20
  6. pH Adjustment: General Hydroponics pH Control Kit
  7. Large Water Container for soaking your media
  8. Small Water Container for holding cuttings
For The Cloning Process
  1. 7” Humidity Dome and Cloning Light:Super Sprouter Deluxe Propagation Kit. You need a 7” tall humidity dome with vents and a low powered CFL or LED light. This kit includes it all.
  2. Seedling Heat Mat: Vivosun Waterproof Seedling Heat Mat
  3. Heat Mat Controller: Vivosun Heat Mat Thermostat Controller
  4. Spray Bottle (optional): Planted Perfect Pressure Sprayer

Step By Step Cloning Tutorial:

Step 1: Hydration And Presoaking

The first step to cloning is making sure that both the mother plant is well hydrated. Therefore, in the days and hours leading up to the cutting, take extra care to ensure that the mother plant stays well-watered. That water stored inside the cuttings themselves will be the clones’ main source of water.

In addition to hydrating the mother, you need to pre-soak the cloning media of your choice in pH adjusted water. Fill a suitable container with sufficient water to submerge your media. Adjust the pH of the water to between 5.5 and 5.8 and then soak your media in it.

With all the media options, we recommend soaking for 12-24 hours prior to use. Many rockwool products start with a high pH because it is contaminated with lime during manufacturing. They will require a long soak to create a stable pH in the media. The Grodan Rockwool Cubes, which we recommend, are prepared and do not require ph adjustment. However, a long soak does not hurt. It is also best to give a long soak with Jiffy Pellets and Rapid Rooters because they may appear fully hydrated quickly while the interior regions remain dry.

Purified water is best, but tap water is acceptable for rehydration. Fertilizers are not needed for the pre-soak. The cuttings are not actively growing, and they do not have a root system to take in fertilizers. Adding fertilizers makes the water saltier which decreases the osmotic potential. Rather than helping the plant, this reduces the uptake of water once roots start developing. Adding fertilizers works against the whole process of rooting. However, you can add root stimulating products such as rapid start, seaweed extract, b vitamins and phosphorus.

Step 2: Selecting a branch to cut

Once you have gathered all your materials for the cloning process, it is time to select a branch to cut.

You want to look for branches that have 2-4 nodes. Larger cuttings with mature leaves, will develop more quickly once their roots have established. This is because of the larger surface area of leaves but also the added maturity which allows increased levels of photosynthesis.

Look for cuttings with stems no thicker than a pencil. Stems larger than a pencil tend to be woody and they take much longer to root. An appropriate clone should be able to stand up straight and fit perfectly in a 7” humidity dome.

Select a healthy vigorous branch. When you take a cutting, you are disconnecting the shoot from the main plant and most importantly its root system. Without an active root system, the cutting cannot uptake water, nutrients or fully function in the way it could previously (photosynthesis). To successfully develop roots, the cutting needs to be healthy and contain as much of the valuable resources it needs to increase its chances of root development.

The best cuttings are from the bottom of mothers that are at least a couple months old themselves. Being from the bottom of the plant tends to allow the cutting to root faster. Having a mature mother means that the carbohydrate stored throughout the plant is typically higher and the stems are stronger and more suitable to cloning.

Step 3: Take Cuttings from the Mother Plant

After selecting the branch to be cut, you should take a sharp sterile instrument and perform the amputation. If possible, you should cut through a node at a 45-degree angle. For example, rather than making the cut near where the branch attaches to main stem, it would be better to cut through the first node. Cutting through the node is beneficial because hormones are found in higher concentration in nodes and these hormones will aid in the rooting process. Cutting at a 45-degree angle is important because this increases the surface area of the cut which provides more rooting potential and increased water absorption during development.

A sterile and sharp cutting tool is also important. Bacteria can infect the exposed tissue at the sliced end on the clone or the mother. Therefore, you want to be sure that the tools used for cutting are clean and sterile to prevent contamination. Sharp tools are important because you want to make the cut slice, rather than crush. Crushing the stem causes embolisms which inhibit rooting.

As soon as you take each cutting you should place it directly in a cup of water, as if it were a cut flower. If the cut end is left exposed to the air, then it may lead to air embolisms. Therefore, if you plan to take several cuttings, bring a cup of water with you and place each cutting into the cup as it is cut from the mother. They can remain there temporarily as you finish taking your cuttings and prepare for the next stage. 

Step 4: Prepare the cuttings

After you take all your cuttings, you should prepare them for planting in their new pre-soaked rooting media. We recommend using both a gel and a powder rooting hormone together for best results. Take cuttings one at a time from the water where they are temporarily placed and apply the rooting hormone. First apply the gel to the cut end and then dip it in the rooting powder. This increases adherence and ensures the best probability of success.

Once you have applied your rooting hormone, go ahead and place your new cutting into your media. If your media does not have any premade holes, then use a tool that is of similar size to your cuttings and make a hole for the clone. Insert the clones into the holes firmly but avoid pushing the clone all the way to the bottom. In Jiffy Pellets it is easy to mold the media and create a tight fit. With Rapid Rooters, it is a good idea to rip a small piece off the rooter elsewhere and use it to pack the hole around the stem. Not having a tight fit risks stem rot and rooting failure.

The entire process is stressful to cuttings as they can lose water through transpiration quickly. Make sure you do all your preparations prior to taking your cuttings, so that you can finish the process as quick as possible and limit the amount of water that is lost.

Step 5: Follow Our Fast Cloning Method

Follow the daily instructions below to produce roots in about 7 days and plants that are ready to transplant in less than two weeks.

Our Fast Cloning Method

Day 1:

After you have successfully taken your cuts and popped them into their media, they must be placed into an environment with ideal conditions to support healthy vigorous root formation. This means high humidity, low light levels, and ideal temperatures at the roots. For this you will need your humidity dome and low intensity light source. You may also need a heat mat and heat mat controller.

Place your cuttings into their new humidity dome and close all the vents. You can use a pressure sprayer to mist your dome and cuttings with water if you want, but this is optional. After a few hours, you should start seeing the dome mist up. This is a good sign that humidity is increasing and establishing a perfect climate for your babies.

The ideal media temperature range for clones to develop roots more quickly is 72°F - 75°F (22°C - 24°C). It is helpful to use a heating mat with a thermostat controller to precisely control temperature.

As we explain above, using a low watt CFL or LED is best. The light source should be very low intensity with levels between 60-75umols (5000-6000 lux). Running the lights full time (24/0) helps to maintain consistent internal climate conditions and provides more energy for faster rooting.

Day 2 - 5:

For the first few days you need to do something very very important. Absolutely nothing!

Keep vents closed and maximize humidity, you do not want the plants to dry out while roots are developing.

Be patient. Avoid attempting to check for roots in the first few days, you do not want to upset the fragile roots or dry out the plants too much by removing the lid. It can be nerve racking not knowing how things are going, but exercise trust and patience. If you break this rule and open the dome to check on your clones, you are sure to seriously hurt their chances of successful rooting.

Day 6:

By day 6 you can finally lift your lid and inspect your girls. Check to make sure nothing obvious has gone wrong, if the media has dried out go ahead and squirt some water at the bottom until hydrated. Check for signs of White Powdery Mildew and remove any affect areas. Quickly put the lid back on.

Day 7:

You may start seeing roots today, but it is best not to handle them just yet as they will still be fragile. Water the media if dry.

On day 7 you should start to slowly acclimatize your clones by opening the vents on the humidity dome half way. Acclimatizing to a lower RH is important so that the cuttings can start to transpire, pull water and dry out the media. This is a necessary process to stimulate further root development. However, be careful and pay close attention to the plants when you first start to acclimatize them. If there are any signs of wilting, go ahead and close those vents back up. Signs of wilting after opening the vents means that the roots may not have developed enough to sustain proper turgor pressure and hydration from transpiration.

Day 8-11:

By day 8, you should start seeing roots developing in some of the clones and be able to work your way to opening your vents more and eventually taking the lid off. Again, take caution and if you see any signs of wilting, replace the dome and give them another couple of days. Not all clones will follow the same timeline and some genetics may require more or less time with the lid on.

Day 12 - 14:

By day 12-14 the plants should be fully climatized and capable of doing fine outside of the humidity dome. 

Roots should be coming out of the media and the plant is ready for transplant and main vegetation.  While they are ready for transplant, they are not quite ready for full strength light. Allow them to adapt to their new environment and progressively work your way up to full light intensity.

At this stage you have successfully completed your cloning journey. We recommend that you read our article “Why You Should Train Cannabis Plants” to help determine what to do next!

Good luck with your next journey and happy growing.

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Author: Dr Photon

"Being wrong is an opportunity for getting things right."