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.