Unlike humans, plants have the ability to grow missing parts, because every cell within the plant contains the genetic information required to re-grow any part of the plant. Given the right conditions, stems can grow new roots, leaves can grow stems and roots, and roots can grow stems and leaves – incredible!
You will have experienced plants re-growing missing parts whenever you have pruned or topped your own plants. Pruning creates stress for the plant that triggers a hormonal response, leading to a flurry of new growth.
Cloning is commonly done by taking cuttings. A small portion of stem and leaf is cut from the mother plant; then, the cut stem is dipped in a rooting hormone – usually a powder or gel – and grown on.
How Plants Reproduce
Plants can reproduce in two ways: sexually and asexually. Sexual reproduction involves growing plants from seed. The seed will contain genetics from two or more plants. Just like in humans, the dominant genes will win out and the new plant will contain characteristics from the ‘parent plants’. In humans this dictates eye color, facial features and height. In plants it dictates resistance to disease, yield capability and growth rates.
Cannabis seed banks work long and hard to ensure that positive characteristics – such as strong growth, THC content and uniformity – are dominant amongst the seeds that they sell. This ensures that the seeds you buy yield plants that are close to the description on the packet. Ultimately, though, each seed has the potential to be slightly different to another.
Asexual reproduction involves making an exact copy of the main host. Plants produced asexually will contain exactly the same characteristics as the mother plant, because they are a genetic copy of that plant. A well-known example of asexual reproduction occurring in nature is strawberries. Strawberry plants can reproduce by sending out ‘runners’: a long, vine-like branch that produces nodes and eventually roots itself near to the mother plant. Lots of plants that don’t send out runners (including our favorite plant!) can also reproduce asexually. This is done by cloning.
So, what exactly does cloning involve? Put simply, it involves taking cuttings from the mother plant which, when rooted and grown, will replicate the same genetic characteristics as the mother. If you have a plant that is displaying favorable characteristics like strong horizontal growth, resistance to disease – or you simply want to grow another crop of that plant again because it is reacting favorably to your growing environment – then take some cuttings, and clone it.
The Benefits of Cloning
Predictability: If you have had success with a particular plant and take cuttings from that plant, you know that the clones will react to your growing environment and input in the same way as the original plant. You will be more likely to replicate your previous success.
Uniformity: If your crop is made up entirely of clones from one plant, then they should grow identically and be ready to harvest at the same time. There is no need to move them around under lights because they are all at different heights, or postpone your harvest date as you wait for a few plants to mature.
Shorter growth cycles: Once a clone is rooted out, it is ready to transplant and go into the vegging room. Propagation time is far shorter than when growing from seed; you can save yourself up to two weeks. In fact, some growers using hydroponic techniques such as aeroponics or NFT will take large numbers of clones, root them, place them into the hydro system and give them a couple of days to adjust, then switch straight to flower for a ‘Sea of Green’ (SOG).
Maintain a strain: If you really love a certain strain and don’t want to risk losing it, keep a mother plant from which to take cuttings. Some original strains are clone-only and (if you want the original) therefore must be raised from clones.
How to Clone with Cuttings
Cloning is far simpler than you might think, and it is as relevant to the small-scale gardener cultivating four plants for him- or herself as it is for the commercial grower with 50 lights.
First, select the plant you want to clone. The plant needs to be in good health and free from pest infestation or disease. If you pick an unhealthy plant to clone from, you’re screwed from the start! Remember that clones taken from a diseased plant will be carrying the same disease as the mother.
Once you have selected your plant, look for areas of new growth. New growth is the best for cloning as it tends to be softer and less ‘woody’, and so should root quicker – although any healthy stem with a couple of leaf sets will work. Also, ensure that the mother plant is well hydrated, as plants that are dry will not yield a healthy cutting.
Another important factor is the stage of growth. When you take a cutting, that cutting is at the exact same stage of the plant life cycle as the mother plant it was taken from. If you take a cutting from a flowering plant, then that cutting is in the flowering stage and will continue to flower! It’s possible to switch the plant back to the vegetative stage by growing it under 18 hours of light (or preferably more); however this can stress the plant and lead to growth issues. It is much better to take cuttings from plants in the vegetative stage before they are switched to flowering or, even better, keep a mother plant in a perpetual state of vegetation and use this as your source of clones.
Don’t take cuttings from, or attempt to clone, an auto-flowering plant; it will be flowering as it roots out, which causes developmental issues and – more importantly – it can yield very little.
One of the most important factors in taking cuttings is hygiene. A new cutting is vulnerable to pathogens entering through the open tissue at the base of the stem. Using dirty tools or working in a dirty environment is a surefire way of introducing fungal or bacterial pathogens to your clones. Make sure that you spend an extra few minutes cleaning your cutting tools and cutting area and you will be rewarded with healthy cuttings that root quickly.
If you are using a growing medium such as soil, cocos or rockwool to raise clones, then it is very important to maintain the correct levels of moisture in the medium and humidity in the air. Use some form of propagator, even if it’s just small plastic bags placed over each plant. A heated propagator with a lid is best, as the warmth stimulates root growth and the lid maintains humidity and prevents the medium from drying out. Use the vents in the lid to ensure that the environment isn’t too moist as this can cause rot or ‘damping off’. It is a balancing act, but give it a few tries and you’ll master it!
Hydroponic cloning machines maintain the moisture balance for you and take out some of the guesswork. They involve placing the cuttings into neoprene collars and then into small baskets, which are suspended above a nutrient tank. The stems are misted with the nutrient solution and root out faster than in traditional propagation methods. You can save yourself three to five days using a cloning machine. They can range in size from spaces for a few clones to over 100, and the better ones on the market come with a lid.
How to Keep a Mother Plant
Maintaining a mother plant is fairly inexpensive and straightforward. A well-tended mother can be kept for a couple of years if treated correctly.
Keep a separate mother room: Mother plants need to be kept in the vegetative stage of growth on 18 hours (or even 20 hours) of light; this means they’ll need to be kept out of the flowering room. Grow tents are a great option as several plants can be kept in a light-tight environment close to, or even within, your main room.
Choose the correct lighting: Plant lighting that is at the blue end of the spectrum encourages vegetative growth, so if using an HID lighting system choose a metal halide bulb. If you’re only keeping one or two mother plants, a blue CFL lamp or large T5 propagation lamp will be more than adequate and will cut down on heat.
Choose the correct growing media: You can keep a mother for a long time if you wish, but long term plants will need a healthy root zone. If you want to hand-water, choose a light and aerated medium that won’t compact over time – such as cocos or a light potting soil. If you wish to use a hydroponic system, go for one that allows you to use inert clay pebbles – a drip feed system or ‘ebb and flow’. This will ensure that there is plenty of oxygen around the roots.
Choose the correct feed: A nitrogen-rich grow formulation will be required as your base nutrient. Make sure you use an enzyme product periodically to break down old roots and keep the root zone clean.
Cloning Top Tips
If using a mother plant, give it a good spray with a nitrogen-based foliar feed, one or two weeks before you are due to take your cuttings. This will ensure that there is plenty of healthy, new growth from which to select your clones.
Keep your cloning area separate from your main growing area. This will prevent any airborne pathogens present in the main room from entering your new clones. Remember that healthy, mature plants may not show any sign of disease, but pathogens may still be present.
Prep your area: you’ll need a sharp scalpel or razor blade, a container of water at pH 5.5 – 6, rooting hormone, a clean mat and your propagation medium or cloning machine.
Take your cuttings: select a 3” or 4” stem complete with a few leaves; cut just below where the leaves join the stem (this ‘internode’ is where your clone will produce roots) and place the cutting into the container of water. Repeat until you have all your cuttings.
Slice off the lower leaves where they join the stem and just leave a few leaves at the top of the cutting. Remember that the leaves require energy to maintain them, and you want the majority of the cuttings’ energy to go into root growth. So, if the leaves on the cutting are quite large, cut off the tip, about halfway down the leaf. Less leaf area requires less energy to maintain it.
Use a scalpel or razor blade to cut the base of the stem diagonally, ensuring the blade is very sharp – this will avoid crushing the stem.
Dip the stem in rooting hormone. Always pour an amount of powder or gel into a small container (or lid) to dip the cuttings. Don’t dip into the main container or you may contaminate your entire supply of hormone. Throw any excess gel or powder away, do not pour it back into the main container.
Gently slide your cutting into its propagation medium and place it into a propagator. Roots will develop with three to seven days. If using a cloning machine, slip the cutting into the neoprene collar and turn on the pump. Do not add nutrients to the reservoir until you see the first signs of root development, usually after three to five days.
So, there you have it – cloning is an easy way to ensure your crop is healthy, develops at the same pace and is ready to harvest at the same time. Plus, it’s good fun! Happy cloning!