Cloning For Hydroponic Growers
Cloning is one thing that many growers struggle with. However, in reality, cloning isn’t so hard as long as best practice principles are adhered to. These best practices basically are:
The Short Version of Getting Cloning Right
- Air temperature – overly cool or overly warm temperatures will stress cuttings and result in low strike rates. Keep the propagator temperature above 22°C (71.6°F) but don’t let it exceed 26oC (78.8°F)
- Relative humidity –cuttings require high air humidity (> 85%) to reduce transpiration
- Root zone temperature – by having slightly warmer root temperature than air temperature this helps in striking clones. Heat pads help create a slightly warmer root zone area temperature because the source of heat for propagation is directly beneath the cuttings. Optimal root zone temperature for herbaceous cuttings (e.g. cannabis) tends to be about 25 – 27° C (77 – 80.6° F). It is important not to allow the rooting zone temperature to go above 28° C as this can starve out oxygen and create and environment where fungal pathogens can damage/rot the lower stem of the cutting
- Root zone oxygen – a combination of overly warm and over saturated growing media is without a doubt the number one cause of low (or no) strike rates. Much like older plants clones need adequate oxygen in the root zone for health. For this reason, it is important not to over saturate the media and have temperatures too warm in the rooting zone
- Light intensity – cuttings don’t like intense light. Using fluorescent T5 lamps above a propagator is recommended.
- Light colour/spectrum – 5500 – 6500 degrees kelvin lighting is optimal for cloning
- 18/6 light cycle – some recommend a 24-hour light cycle for cuttings. I definitely do not. After many years of cloning I have found that some night (lights out) hours help to reduce the stress placed on cuttings while they produce roots. This leads to, overall, healthier clones and higher strike rates.
- Cutting material – cuttings need to be taken from a healthy donor plant. You should avoid takings cuttings from a diseased, stressed, or overfed plants. If the donour material is stressed so too will be the clone/cutting. As a result, strike rates will suffer.
- Size of cutting and leaf area – don’t take big cuttings with large stems and numerous leaves; go for smaller cuttings around 2-3 inches in length with 2 to 3 leaves.
- Plantlet hole – don’t allow the cutting to flop around loosely in the planting hole. Ensure the cutting is firmly inserted and stable. Make your own off-center planting hole if the existing one is too big.
- Hygiene – to reduce the chances of plant disease during cloning. all equipment used should be as sterile as possible. This means washing propagators and trays in a bleach solution prior to use, and by using a sterile scalpel blade when taking the cuttings.
The Long Version – Getting the Theory Down
Overview of Cloning
Cloning, as the name suggests, is when growers clone their favourite genetics. A clone is a cutting—i.e. a severed part of the plant—that grows roots and eventually stabilizes as a genetic replica of the plant it was cut from. This is possible because each of the clone’s individual cells contain all of the genetic information necessary to reconstruct the whole plant as a genetic copy of the plant it was cut from. This means that any branch, leaf, stem or flower can generate genetic copies.
The ability to successfully clone a plant enables growers to continue using a variety of plant that, for one reason or another, has desirable genetic traits. For example, when growing from seed there can be multiple genetic variations, known as phenotypes, among any one batch of seeds produced from the same parents. One of these phenotypes might be more vigorous, may finish earlier, produce more and yield a higher quality end-product than the other plants. Cloning enables growers to take cuttings from this preferred phenotype and genetically replicate it over successive crop cycles.
This means we are able to save and regrow favoured genetic material through cloning.
Healthy Clones for Healthy Yields
The clone stage of growth is crucial. It is during this stage that the foundation for the plant’s entire life cycle is built. Plants which are stressed or unhealthy during this early stage of development are more likely to remain stressed and unhealthy during later stages of growth. Clones which are reared properly will better transition into the later stages of growth more seamlessly. Smooth transitions equate to not only healthier plants and larger yields, but also increased efficiency. Plants that are stressed or lagging during crucial transitional periods will be slower to develop and will be potentially one step behind the rest of their life cycle.
The process of cloning – cutting and striking plant tissue – can be very stressful for the clones. As a result, striking healthy clones is something that many novice gardeners struggle with.
For this reason, let’s give this one some serious attention.
Principles that Underpin Successful Cloning
Successful cloning requires starting with high-quality, uniform cuttings, not excessively large and free of insects, diseases and viruses. Cuttings not of high quality can lead to delayed and non-uniform rooting. Starting with variable clones often produces variable height and bulk finished plants.
Starting/cutting material should always be taken from a healthy plant or plants. Taking cuttings from an unhealthy, stressed plant will reduce your chances of success.
Clones that are struck from unhealthy starting material may go on to grow into unhealthy, low yielding plants.
High Humidity in the Cloning Environment
When a cutting is taken from a plant the cutting is left without a root system. The root system is responsible for pumping water and nutrients to the plant. This means that roots deliver water to the leaf tissue of a plant. Without roots, a plant is forced to maintain water within its tissues through other means. If the environment around the plant isn’t ideal for this, without a root system, a plant will quickly lose water from its leaves into the atmosphere around it and, as a result, it will wilt, dry out and eventually die.
Because a cutting has no roots its stops producing vegetative growth and instead directs all of its energy towards survival. Survival for a cutting that has no roots means the cutting directs all of its energy towards producing new roots so it can become self-sustaining and once again have a root system that enables it to pump water and nutrients to its leaves. However, producing new roots takes several days (approximately 7 to 10 days) and until then the cutting has to somehow maintain water in its tissues in order to survive.
One very important factor that will help the plant survive without a root system is high humidity. This is because when the relative humidity in a plant’s environment rises, water loss through its leaves is greatly reduced, while a decrease in humidity causes the water loss rate to rise. Air that is very humid does not accept water vapor easily, while drier air makes it easier for a plant to release water by evaporation through the stomata on its external surfaces.
High Humidity (above 85%) in the cloning environment is crucial because high humidity (high water percentage) in the air surrounding the clones reduces transpiration and stops the cuttings from drying out and wilting. High humidity is maintained through the heat that the Clone Station’s water pump creates (warming the water) and through the use of the Clone Station’s closed transparent plastic lid which traps and holds humidity in the air enclosed within the lid.
An increase in the air temperature warms the water inside leaves more quickly causing it to evaporate more quickly.
Therefore, excessively warm air temperatures can cause cuttings to dry out before roots can form to replace the water.
When cloning, heat is applied to the bottoms of cuttings, rather than by heating the air around them. Providing bottom heat optimizes the growth of the new roots without adding excessive heat to the air and therefore potentially drying out the tops of the plants.
One of the key reason’s growers have problems with cloning is that they try to propagate cuttings in overly warm environments. This places undue stress on the clones during the crucial period in which they are trying to form roots. Air temperatures need to be carefully monitored and controlled. Ideally clones should be maintained in an environment where air temperatures don’t exceed 24 -26° C (75.2 – 78.8° F).
Maintaining air temperature lower than root zone temperature retards shoot growth and promotes root development; therefore, ideally air temperatures are slightly lower than root zone temperatures.
Root Zone Temperatures
Bottom heat is used to propagate clones to keep the top of the cutting dormant and induce root growth at the stem base.
It is important to note that root zone temperature is a critical factor in striking clones. For this reason, during propagation, measuring and managing root-zone temperatures should be given a high priority. And, while different temperatures are optimal for different species, the common rooting temperature target for most species is between 23 – 26° C (74 to 79° F). Optimal temperature for short season, herbaceous crops (e.g. cannabis) tends to be about 25 – 27° C (77 – 80.6° F).
Higher temperatures than these, up to about 82.4 – 86° F (28 – 30° C), may even stimulate quicker root development; however, as temperature increases around the stems of cuttings so too does the chances of the cuttings becoming infected by fungal pathogens, which results in stem rot at the base of the cutting. If clones do get stem rot this results in most instances with the clones dying. For this reason, growers should be cautious not to allow temperature to rise too far above the stated optimal levels of 25 – 27° C (77 – 80.6° F).
Oxygen Moisture Ratio in the Rooting Area
Maintaining high oxygen levels around the stems and developing roots of clones is extremely important. One mistake that many growers make, when cloning, is over-wetting the clone’s rooting area which results in low oxygen levels and low strike rates. High moisture, low oxygen conditions have been shown to negatively affect the hormone balance of cuttings leading to slow rooting and unhealthy clones. Studies have consistently shown that where high oxygen content is present along with adequate moisture, clones are placed under less stress and produce healthier roots earlier. For this reason, ensuring adequate oxygen is available around the lower stems of clones is imperative.
Lighting – Moderate light levels
Clones are best propagated under lowlight levels. HID lighting or direct sunlight is too intense for clones and will ultimately stress them and/or dry them out, resulting in low strike rates.
Typically, growers use fluorescent lighting or some other form of low light output system (e.g. CFL, LED) for cloning. When roots have formed and new leaf growth begins more intense light can be introduced to stimulate further vegetative growth.
The ideal light colour spectrum for cloning tends to be at between 5500 – 6500 degrees kelvin. Specialized fluorescent tubes (and CFL, LED) for cloning are available through hydroponic stores. Speak to your supplier about product options.
An 18/6 Light Cycle
The light cycle for clones is best handled at 18 hours on, 6 hours off.
In some cases growers use a 24 hour light cycle during cloning. This is largely done in order to maintain constant heating for the clones (i.e. heat is produced by the lighting). However, the 18/6 light cycle tends to be a bit more gentle on clones, creating less stress and allowing high humidity and darkness to give them some rest during the crucial period in which they are forming new roots. Clones are just like people – they appreciate a bit of sleep.
Cutting Material – How to Cut
The growth hormones responsible for the rooting of cuttings are called auxins. These hormones stimulate root initiation and development. Auxins are naturally occurring in plants and they are found at the highest levels in the parts of a plant that are growing most actively. This means that the main stem top – the terminal bud – and the lateral branching tips of the plant are where the highest levels of auxins are found. When a cutting is taken from these areas, the auxins that are present in the leaf and bud material at the top of the stems are transported to the base of the cutting where they go to work to help form new roots.
Another area of the plant that is important in cloning is the axillary bud. Axillary buds grow into lateral branches so where axillary buds form is an area where high levels of hormonal activity and growth take place. Axillary buds are found where the leaf petiole meets the stem of the plant. This area of the plant is called the axil (hence axillary bud) or the node. The distance between axillary buds/nodes is called the internode.
When cutting clones it is wise to use the areas of the plant where the most hormonal/growth activity takes place to aid the striking of new roots. This means if we cut the tops of branches just below the axillary buds we are getting two areas on the plant where high levels of hormonal activity and growth occur. See following image.
Looking at the above image you can see that we have made a cut leaving the growing tip of the plant intact while cutting just below the next set of leaves where the axil or node point is. This would be our first cut in taking clone material. We would then use a scalpel blade to remove the lower leaves and gently cut or scrape away the axillary buds leaving the lower area of the stem cleaned of leaf and bud material. By removing this material we would have exposed stem tissue. See following image
Looking at this image we can see the exposed stem tissue is where the axillary buds/nodes once were. This is an area where high levels of growth and hormonal activity occur. Therefore, the exposed stem tissue becomes the point at which new roots form and grow.
The Best Material for Cutting
Slightly more mature, semi-hard branches make for the best cutting material. This means that new shoots on younger plants, which tend to be soft, supple tissue, can be a bit harder to strike than cuts that are taken from woodier, more mature material.
Plants that are fed high levels of nitrogen (N) tend to produce very supple growth/tissue which makes this material harder to strike than semi hard tissue that is produced using less N and more P (phosphorous) and K (potassium). For this reason, where growing mother plants for dedicated use in cloning it is advisable to use a bloom formula, rather than a high N grow formula, for plant nutrition.
Stressed plants make for less than ideal cutting material while healthy plants provide healthy clone material. Always strive to cut from healthy plants and only take healthy, strong material from these plants.
Reduce Leaf Biomass to Reduce Stress
As a rule, the more biomass (i.e. stem, leaf and bud material) on a plant, the larger the root system it needs to sustain this biomass.
Because a cutting lacks a root system, excess leaf material on the cutting increases the energy demand on it. This can easily place an unrooted clone under stress.
While some top growth is necessary for a cutting to survive, too many leaves on a cutting creates excess demand for water. This commonly causes cuttings/clones to wilt and ultimately leads to longer striking periods and reduced strike rates. Therefore, when cloning, remove larger shade leaves completely from the cutting.
A commonly used practice by hydroponic growers is to remove leaf tips (basically cut off the ends of leaves, leaving half a leaf) to reduce the size of larger leaves on the cuttings. However, a recent study found that removing leaf tips reduced rooting success rate from 71% to 53% without influencing root quality. Additionally, clones with 3 fully expanded leaves developed significantly larger roots than those with 2 fully expanded leaves, but both of these groups had the same rooting success rate. The observed quality improvement was likely caused by the additional carbohydrates and other factors that were stored in that extra leaf and made available as fuel for the growth of the developing roots. *ref.1(
Additional Auxins to Stimulate New Root Growth
As noted, auxins are the hormones that stimulate root growth. When a cutting is taken from a plant, the auxins in the growing tip of the cutting are transported downwards to the freshly cut stem base to begin the process of cell differentiation to initiate root cell development. While the plant contains small amounts of auxins stored in the newly expanding tissues, applying further auxins directly to the cut portion of the plant will greatly increase rooting/striking potential. This is why growers who clone plants from cuttings utilize rooting gels, powders, and dips that contain auxins (typically IBA or NAA or both) to increase root initiation and vigor of root formation.
Therefore, when propagating clones, always apply a rooting hormone product to the base of your cuttings before placing them in rockwool blocks or aeroponic propagators.
Cleanliness is Next to Godliness – Use sterile, clean equipment
Taking cuttings from your plants can be likened to performing surgery. Every cut made is an open wound that is susceptible to infection and needs to be treated with care. All of the same concerns that a person would have prior to undergoing surgery are equally valid for your plants and the material cut from them.
When taking cuts for clones always use a sterilised scalpel blade and wear surgical gloves. Sterilise any other pieces of equipment that will come into contact with cuttings.
Easily Accessible Sterilising Agents include:
Common household bleach (sodium hypochlorite or chlorine) – recommended because it is cheap, readily accessible and very effective
Monochloramine – e.g. Pythoff
Hydrogen Peroxide – e.g. Hygen Peroxide, Oxyplus
Time of Cutting – Cutting Material
Cuttings are best taken from fully vegetative plants (i.e. plants that are in the 18/6 light cycle). While it is possible to cut from plants that are in flowering mode, what this means is that because the plant has switched to flowering hormonally it can take some time under a vegetative 18/6 light cycle to transition a flowering cut back into a vegetative plant. In the process, a clone cut from a flowering plant tends to have a lag phase of a week or so (i.e. growth ceases) before it starts producing single pronged leaves, then three pronged leaves before finally producing normal vegetative growth. Further, a clone cut from a flowering plant tends to shoot out a lot of abnormal branching (causing it to grow extremely bushy) while switching back from flower to vegetative mode. In some cases growers see this as a benefit and cut from flowering plants purposefully in order to produce larger, bushier plants. This is often referred to as ‘Monster Cropping’.
It is inadvisable to induce flowering during the stage the clone is growing out from flowering to vegetative mode because this can result in the early induction of full flowering and, as a result, stunted plants re height and growth formation. What this means, often, is that a plant grown from a flowering clone cannot be switched down into flower until it is quite tall. This makes cuts from flowering plants less than desirable for growers who wish to finish their plants small (e.g. SOG growers).
Often growers keep vegetative mother plants which are used for cutting material. This is the best scenario. In other cases, growers who grow large vegetative plants cut clones from the plants while they are still in vegetative mode.
In other cases, growers who are growing smaller vegetative plants before switching to the 12/12 light cycle, tip/top their plants while they are in vegetative mode. These tips/tops are then used for clones. In yet other cases, growers might take cuts a week or two into flower. However, in this scenario, growers risk taking cuts which are hormonally in flower and, as a result, need to be revegged before being turned down into flower once again.
Some theory covered, what I’ll do now is put in an illustrated step-by-step guide to cloning. The method I’ll outline is using rockwool cubes. After this, I’ll talk a bit about aero cloning which is becoming more and more popular with growers.
Step-By-Step Cloning Guide
Because clones begin life without root systems there needs to be some specialised equipment used and care taken to reduce the stress that the clones will suffer during the striking stage.
The root zone should be kept warm at 25 – 27° C (77 – 80.6° F) through the use of a heat pad or a similar system. The heat pad should be a high quality one with a thermostatic control that can be manually set to a desired temperature. Cheaper heat pads that don’t have a thermostatic control should be avoided because these units operate at a few degrees above ambient air temperature; therefore, if the ambient air temperature in the environment is 26 oC (78.8 oF) the heat pad will be operating at about 29 – 30 oC (84.2 – 86 oF), which is far too warm. Basically, cheaper heat pads without thermostatic control offer very little in the way of accurately controlling root zone temperatures under varying ambient air temperatures. For what it’s worth, spending a few bucks more on a decent heat pad will save you a lot of grief later.
The cuttings should be kept in a very humid environment to ensure that they don’t dry out. The air temp within this environment should be kept at ideally between 24 – 26 oC (75.2 – 78.8oC).
Equipment Needed for Cloning
- Fluorescent light (T5 etc) at ideally 6400 – 6500 degrees Kelvin
- Sterile Scalpel Blade
- Clone Gel or Powder (Rooting Hormone)
- Bucket of tepid water (Approx 24 oC/75.2 oF)
- Propagator Lid
- Air temperature thermometer
- Seedling tray
- Thermostatically controlled heat mat
- White Shade cloth or other light diffusion material (approx 30 – 50% light diffusion material)
- Small amount of Bloom nutrient if using RO, rain or distilled water (1/4 strength)
- Rockwool Propagating blocks
- pH Up/Down
NOTE – Some rockwool cubes have premade holes. The holes are often too large for the circumference of the cutting’s stem. It is recommended that you make smaller holes yourself to accommodate the stem with a snug fit.
Above – an ideal propagator setup for cloning. Note the air temp thermometer. Air temperatures during cloning are critical to success. It is wise, therefore, to monitor air temp.
PREP BEFORE CUTTING
Wet heat pad mat with water and set at 25 -26 oC (77 – 79 oF) at least 8 hrs prior to taking your cuttings. Place propagator lid on top of the seedling tray. Close vents on propagator and ensure good air seal. Any air gaps in the vents will let the humidity out. As a tip, I use a transparent tape (e.g. Sellotape) to tape the vents and close off any air gaps completely. This ensures humidity is unable to escape from the propagator.
Soak rock wool cubes in water that is pH adjusted to 5.2 – 5.5. The cubes are very alkaline so you will need to soak them overnight to ensure that they are at the correct pH for cloning. If you are using RO, rain, or distilled water use a very diluted bloom solution for soaking (EC approx. 0.2 at pH 5.2 – 5.5).
DAY OF CUTTING
Remove the rockwool cubes from the water that you soaked them in. Gently squeeze out the excess water. Cuttings will do better in a moist cube than they will in a saturated one. Remember, moist not soaked! A one inch Grodan cube should weigh approx 40 – 45 Grams (approx 35 – 40ml of water added to block) when suitably moist.
- Fill bucket with tepid water (Approx 24 oC)
- Pour clone juice into cap
- Sterilise any scalpel blades that you have used before (It is recommended that you use new blades each time you begin a new set of cuttings)
You are now ready to begin removing material from the plants for your cuttings.
Cut off the top of a lateral (with scissors or scalpel) so that it has at least 2 sets of leaves left on it. Your cutting should now have the top leaf material and at least one other set of leaves below with a node (young shoot or beginning of new lateral) above each leaf.
Keeping your scalpel blade flush with the stem, cut away the bottom node/s and the leaf. You should now be left with at least one set of leaves or growing tip above where you just cut.
Approximately 5mm beneath where the nodes were slice through the stem on a 45-degree angle. See following image which outlines preparing the base of the cutting for cloning.
The growth layer of the plant is called the Cambium layer. It is the cambium layer that is responsible for cell division and it is the Cambium layer that will be responsible for producing roots. The cambium layer is just below the outer green tissue on the stem. By gently and carefully scraping off the outer green tissue on the stem you expose the cambium layer on the cutting. This practice (wounding) encourages new root growth to occur more quickly. One study on cannabis cloning found wounded stems were 162% more likely to root than unwounded stems and rooted 1.5 days earlier. *ref.2* Therefore, gently scrape the circumference of the cutting (with the scalpel) from the node to the base of the stem. Scratching away the stems outer green tissue will stimulate further rooting. See following picture.
If you still have a lot of leaf material left on the cutting, remove some of it leaving ideally 2 to 3 leaves on the cut.
Dip the base of the cutting in the clone juice. Ensure that the clone juice covers the now removed nodes and scraped to the base of the stem. See following image….
Place the cutting into the rockwool. Ensure that the stem is securely in place (snug fit) and that nodes are at least 3mm below the surface of the rockwool. See following image
The cutting is now complete. Place it under the propagating lid right away. The vents on the propagator lid must be closed tightly (or taped over with a transparent tape recommended) to ensure humidity is contained within the propagator. See following image….
Light, Humidity, Action
When you have completed cutting set your fluorescent light/s to run 18 hrs a day (e.g. 4pm –10am). Cover the propagator lid top with your shade cloth or other light diffusion material (Approx 30 – 50% light diffusion). This will ensure the clones receive a very soft, diffused light for the first few days.
This period is critical. It is important that the cutting is in an environment that is very humid. This will ensure that the moisture within the cutting does not transpire into its surrounding atmosphere. A thermometer in the propagator will help with keeping an eye on temperature. This should be around 24-26 oC (75 – 78.8 oF).
Follow this guide
Day 1-4 – Make sure humidity is still forming on the propagator lid. Ensure the rockwool blocks are retaining moisture. Ensure ambient air temperature within the propagator lid is within optimal range. As the heat pad mat begins to dry apply more water to it. This water is heated and becomes humidity in the propagator. Therefore, by having water on the heat mat this helps to ensure high humidity in the propagator.
Day 5 onwards – On day 5 remove the light diffusion material (e.g. shade cloth) from propagator lid. Ensure the rockwool blocks are retaining moisture. Where they begin to dry apply more water. pH adjust this water to approximately pH 6.0 before applying. Be sure not to saturate the blocks but to just have them moist. If they become saturated, gently (I stress gently) squeeze out some of the water until moisture is suitable. Ensure ambient air temperature within the propagator lid is within optimal range.
Day 7 – 14 – Generally, if the process has been done correctly, the first sign of roots should become apparent at day 5 to day 10. However, over the years, I have found some genetics strike very quickly while others can take longer. The key is patience and ensuring that all of the environmental parameters (air temp, root zone temp, humidity, moisture in the clone blocks) are maintained within ideals while you are waiting for the clones to strike. Once your cuttings have produced roots, slowly adjust them to their new growing environment by slowly opening humidity control vents. Open the top vent first for two days and then open the side vents for 2 – 4 days before removing the propagator lid completely. This helps the clones to slowly adapt to a lower humidity environment outside of a propagator (e.g. a grow room where humidity is lower).
Assuming your cuttings are thriving without the help of a propagating lid you can now begin giving them a weak bloom nutrient to stimulate some growth. As a tip, there are cloning solutions sold through stores. There’s no need to spend money on one of these products. A diluted bloom nutrient does the job just fine.
Tip: The roots of the clones ‘brown off’ when exposed to air and light. This means that once clones have rooted in 1-inch blocks and the roots are showing through the blocks they quickly begin browning off. This prevents the clones from growing and can negatively affect plant health. For this reason, if you are wanting to vegetate/grow the clones while in rockwool blocks, 1-inch cubes can be placed into larger 4-inch or even 6-inch cubes. For example, I use 6-inch cubes and grow quite large plants in these cubes. From there, these mature vegetated plants can be placed into the system and switched straight into 12/12 (bloom).
Breaking In – when first placing the young cuttings into the growing system
Once you have created healthy cuttings in your propagation area, break them into your grow room gently. When using high wattage HID lights, keep them raised up high initially. If you’re using multiple lights you may not need them all on. Try to keep the humidity high (approx. 80 – 85%) and temperatures moderate (approx. 24- 25oC) to give your new plants the best, least stressful start possible. After about 7 – 10 days of breaking in, lights can be lowered and standard optimum room temperature and humidity is the go.
Aero Cloning Systems (e.g. Turbo Klone, Clone Station, Aero Cloner)
Aero cloning has a large following these days. Therefore, I just wanted to touch on a couple of important points when using aeroponic cloning systems. Firstly, the same optimum air temperatures and root zone temperatures apply as those we have just covered. As such, there is no need to talk about aero cloning specifically as being completely separate re optimums versus cloning in rockwool blocks. However, several points to be aware of are:
- the water pump in the aero cloning unit acts as a heater, often making the water and root zone temperature too warm. Therefore, many growers have the water pump turning on and off via a timer to allow for heating and cooling of the aero cloner’s solution. This is something that aero cloners need to be aware of and adapt the times the pump turns on and off as necessary. For example, some growers will have the pump turn on for 15 minutes every hour. Ideals though will be determined by the ambient air temperature. I.e. where the air temperature is cold more heating through the water pump is required than where the air temperature is warmer.
- Because the water pump in aero cloners has a tendency to make the water too warm, a wise investment (a must have piece of equipment as far as I am concerned) for aero cloning is a reasonably cheap digital water thermometer that has a separate probe. The probe (which measures the temperature) can be placed in the reservoir of the aero cloner while the digital thermometer (which displays the temperature) can be placed outside of the aero cloner making accurate water/reservoir temperature monitoring dead easy. Speak to your hydroponic supplier about product options.
- Regularly check that the sprayers and pump are delivering a nutrient mist. Any bits of organic debris from stems or emerging roots can plug up finer sprayers.
- An aero cloner might look like a flash bit of equipment but it is only as good as the environment it is used in. As with any other clone propagator, the ambient air temperature of the atmosphere that surrounds the aero cloner is all important. I.e. excessive temperatures outside of the aero cloner will result in excessive temperatures inside the propagator.
- There is no need to add any nutrient to reservoir if using tap/mains water. Cuttings don’t require nutrients until they have formed roots – at this point very low levels of nutrient will stimulate growth, If using demineralized water I do recommend adding a very low amount of bloom nutrient at about 0.2 EC.
- To reduce sprayers blocking, add some hydrogen peroxide or monochloramine to the reservoir. This prevents biofilm (slime) build up and may help in reducing any stem rot issues.
Ref 1. Deron Caplan, Jonathan Stemeroff, Mike Dixon, and Youbin Zheng. Vegetative propagation of cannabis by stem cuttings: effects of leaf number, cutting position, rooting hormone, and leaf tip removal. School of Environmental Sciences, University of Guelph, Journal of Plant Sci. 98: 1126–1132 (2018) dx.doi.org/10.1139/cjps-2018-0038
Ref 2. Campbell LG, Naraine SGU, Dusfresne J (2019) Phenotypic plasticity influences the success of clonal propagation in industrial pharmaceutical Cannabis sativa. PLoS ONE 14(3): e0213434. https://doi.org/10.1371/journal.pone.0213434