Cloning For Hydroponic Growers
A Step-by-Step Guide
Cloning, put simply, can be described as taking a cutting (leaf and stem tissue) from one plant and turning it into a plant in its own right.
Tissue (leaf and stem) is taken from a plant that has desirable genetic traits; this tissue is then encouraged to grow roots (strike) and, in turn, becomes a new plant ready to be grown again.
Through cloning we are able to ensure that our favourite genetics are replicated time and time again; genetic copies (clones) for each and every successive crop.
Which brings us to our next point…
Genetics! Genetics! Genetics!
Genetics will determine the traits expressed by any given plant.
Yield (weight), quality, and crop cycles (finishing times) etc are all, therefore, governed by genetics.
Finding the right genetics and ensuring continuity of these genetics in future crops (along with nurturing these genetics through providing optimized growing conditions – Ie. Environment and nutrition) will ensure fruitful results.
Cloning success (strike rates, health etc) will be reliant on:
The key to cloning success is the oxygen/moisture ratio within the media where the tissue (stem) will be encouraged to produce roots.
The most common mistake made by growers, when cloning, is they over wet the media (rockwool) the cuttings are placed in.
As a rule of thumb a 40x40mmrockwool cube (our media for cloning) should weigh 40 – 45grams when suitably wet/moist.
It is important to cultivate clones in a humid atmosphere. High humidity allows the cuttings to absorb and maintain moisture in/through the leaf tissue; this aids greatly in reducing stress and encouraging healthy clones and high strike rates.
Low humidity may result in clones loosing moisture (transpiring) into the surrounding atmosphere and drying out.
When cloning a ‘propagator’ – a self enclosed unit with a transparent lid – is a must for maintaining humidity in the cloning atmosphere.
(Pic of propagator)
All optimized plant growth is reliant on air and media temperature. This is just as true for cloning.
If the environment is overly warm the clones will suffer stress. The same can be said of an overly cool environment.
The ideal air temperature range for clones lies between 24 – 28 degrees Celsius (75.2- 82.4 F) with 26 degrees C (78.8F) probably being ideal.
Thermostatically controlled Heat Mats or Aerocloner type systems where water is warmed via a water heater should be used to ensure a controlled temperature is maintained in the cloning (propagator) environment.
Clone material/time of cutting
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 most ideal material for cloning possesses:
A) A healthy cambium layer [and]
B) An active/advanced cambium layer
Cutting material should, therefore, be taken from healthy plants (i.e. healthy cambium layer) and be taken from older and more advanced plants where the cambium layer is more advanced and active.
Ideally your cuttings will be taken from semi-woody material. This means the stems are beginning to harden. The best time for cutting clones from the plants is a couple of weeks into the 12/12 light cycle (early flower).
If mother plants are used (plants specifically grown for cloning) the mother plants should be at least 10 weeks of age before clone material is taken. Young, soft tissue does not strike as well as more advanced semi-woody tissue and is less forgiving of ‘environmental stresses’ (warm or cool temperatures etc) that may occur.
pH, put simply, is the measurement of acidity or alkalinity in the growing media and/or nutrient.
pH is measured on a scale of 1 to 14, with pH 1 being extremely acidic and pH 14 extremely alkaline.
The ideal pH for cloning lies between pH 5.5 – pH 5.8 (slightly acidic).
Unused (new) rockwool is alkaline and requires presoaking in a pH 5.3 solution for at least 4 hours before use in cloning. (Presoaking at pH 5.3 will create approximately pH 5.5 – 5.8 in the rockwool clone blocks)
Additionally, whenever water/nutrient solution is added to the clone blocks (or used as a foliar spray) it should be pH adjusted to 5.5 – 5.8.
EC/CF/PPM & Water Quality
EC/CF/PPM are measurements that are used to establish mineral salt content in water/nutrient.
For cloning a low EC is desirable – with no more than 1.5 EC (15 CF/1050 PPM) being ideal.
Water quality should not be underestimated as an important factor in cloning. Ideally, distilled, rain or ‘Reverse Osmosis’ (RO) water (0.0 EC – 0.002 EC) should be used in conjunction with a nutrient or a clone solution to bring the EC to desired levels.
Through this means we are able to guarantee the cuttings only receive optimized nutrition. Tap water (which typically has an EC of 0.3 – 1.2) is made up of various and in some cases harmful salts (sodium, chloride etc). Tap water should not be used for cloning.
Manic Botanix recommends using a clone solution (not to be confused with clone gel) for presoaking clone blocks and moistening/wetting thereafter. These solutions often have rooting hormones incorporated into them, which aids adventurous/prolific root initiation and growth. Other than this they provide low levels of plant nutrition to the clones when roots initiate.
If you choose not to use a clone solution, or cannot purchase clone solution locally, use a ‘1/3 strength bloom solution’ (0.5 – 0.8 EC with RO, rain or distilled water) for hydrating blocks/media and for use as a foliar spray. Bloom solution has higher % of ‘potassium’ (stimulates root growth) and phosphorous and lower % of ‘nitrogen’ (stimulates foliar growth which is not ideal when trying to initiate/stimulate root growth) then a vegetative solution which makes it ideal for striking clones.
Clone Gel Quality Will Aid in Strike Rates and Times
The key to a good cloning gel is the level of auxins contained within the gel. For instance, Manix Cyclone clone gel contains 3g/L of IBA (Indole-3-Butyric Acid), a powerful auxin that is the key to all good rooting compounds.
Additionally Manix Cyclone contains key vitamins that are required for culture growth in tissue culture studies. These being thiamine, pyridoxine and nicotinic acid (Niacin vitamin B3). Thiamine is shown to be essential for culture growth, but the rest are promotive agents. Pantothenic acid is also known to be promoter but it is less used in the tissue culture process.
Sterilize the Water Used For Cloning
Cloning is one area where I do not recommend the use of beneficial bacteria and fungi over sterilizing agents such as hydrogen peroxide or monochloramine – this is particularly true in Aeroclone type systems where the use of beneficials can result in clogging the fine mist sprayers. My preference here is to use hydrogen peroxide over monochloramine.
Light is the energy of photosynthesis. Light provides the energy for growth.
Light can be separated into two types of energy.
Light intensity (lumen): Clones are best cultivated under low light levels – they do not require high (light) energy. In fact, if light levels are too high this will result in stressing the clones and thus lower strike rates and/or total disaster. For this reason Low Intensity lighting (fluorescent) is best suited for cloning.
Light colour (spectrum): Vegetative growth is best stimulated by blue spectrum light. Fluorescent grow tubes with a colour rating of approximately 6400 degrees Kelvin (blue spectrum) are the ideal light source for cloning.
Speak to your supplier about product options.
Quick Recap (optimums)
- Clones should be cut from healthy, older, semi woody material
- 1 inch rock wool cubes should weigh 40 – 45 grams when wet for optimum oxygen/moisture ratio
- A propagator is a must to ensure high humidity…healthy clones = high humidity
- Optimum environmental temp = 24 – 28 degrees C (75.2- 82.4 F) with 26 degrees C (78.8F) probably being the ideal
- Rockwool blocks should be presoaked at pH 5.3 for at least 4 hours prior to use. This leaves the naturally alkaline block at approx pH 5.8
- Optimum pH in blocks = pH 5.5 – 5.8. Each time solution/water is added to blocks it should be pH adjusted to 5.5 – 5.8
- Ideally, distilled, rain or, RO water should be used with a clone solution for soaking and wetting blocks
- Sterilize the water prior to use
- Use a good cloning gel that contains at least 2g/L of IBA
- Low Intensity (fluorescent) lighting with a colour rating of approximately 6400 degrees Kelvin is the ideal light source
So, let’s get down to cloning.
How to Clone
Because clones begin life without root systems there needs to be some specialized 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 (26C/78.8F) through the use of a heat pad or a similar system. The cuttings should be kept in a humid environment to ensure that they don’t dry out. The air temp within this environment should be kept at between 24 – 28 degrees C, 26 C being the ideal.
Equipment Needed for Cloning
- Fluorescent light
- A 240 Volt Timer Unit (HPM etc)
- Sterile Scalpel Blade
- Clone Juice/Gel (rooting hormone)
- Clone solution for presoaking blocks
- Propagator (lid and tray)
- Thermometer for inside of Propagator (a stick on aquarium thermo is ideal)
- Heat Mat
- Rain, RO or Distilled water
- pH Up/Down
- pH Test Kit or pH meter
- 40×402mmRockwool Cultivating Blocks (Grodan, Cultilene etc)
- Spray bottle (500ml/1ltr etc)
PREP BEFORE CUTTING
- Make up a bucket of clone solution (using RO, rain, or distilled water) and pH adjust to 5.3. Add hydrogen peroxide to sterilize the water. Place rockwool blocks in this solution and soak for at least 6 hours.
- Turn on the heat mat/pad and set to 26C (78.8F).
- Add some of your clone solution from the bucket to the spray bottle and dilute 1/1 (half strength solution). Mist the inside of the propagator with the sprayer and place the propagator on the heat mat/pad. Leave for 4 hours before cutting clones. (This will help create humidity in the propagator)
Ready, Set, Go! (Day of Cutting)
- Remove the rockwool cubes from the solution. Gently squeeze out the excess water. Cuttings will do better in a moist cube than they will in a saturated cube. Remember, moist not soaked! A 40×402mmGrodan (Cultilene etc) cube should weigh approximately 40 – 45 grams when suitably moist.
- Pour clone juice into cap
You are now ready to begin removing material from your plants for your cuttings.
- Cut off the top of a lateral (with scissors or a scalpel) so that it has at least 2 sets of leaves left on it.
- Keeping your scalpel blade flush with the stem/outer bark cut away the bottom node/s and the leaf. You should now be left with at least one set of leaves and growing tip above where you just cut.
- Approximately 5mm beneath where the nodes were slice through the stem on a 45 degree angle
- Gently scrape the circumference of the cutting (with the scalpel). Scratching or peeling away the stems outer bark will expose the cambium/growth layer and will stimulate rooting.
- If there is a lot of leaf material on the cutting, remove some of it. You can also cut leaves in half. Reducing the amount of leaf material will mean that the cutting has less mass to sustain. Don’t get carried away with removing too much leaf material. If in doubt just cut the bottom leaves in half. The cutting also needs a reasonable amount of leaf material left on it.
- Dip the base of the cutting in the clone juice. Ensure that the clone juice covers the nodes to the base of the stem
- Place the cutting into the rockwool. Ensure that the stem is securely in place and the node/s are at least 3ml below the surface of the rockwool.
The cutting is now complete. Place it in the propagator. Give it a mist with your spray solution and begin your next cutting following the same steps.
Basic illustration of cambian layer below. Scrape of top green stem tissue to expose the cambian layer and then dip in clone gel.
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.
Light, Humidity, Action
When you have completed cutting your clones set your lights to run 18hrs a day (e.g. 4pm to 10am).
Make sure that you have given the clones a foliar spray and the vents on the propagator are closed.
Check the rockwool blocks every day to ensure they are suitably moist. Give the clones a foliar spray (gently mist them with the spray bottle of half strength clone solution or quarter strength bloom solution) when you do this.
Keep an eye on your thermometer to ensure the cloning environment is not overly warm or overly cool.
After Approximately 7 to 10 days roots should start appearing through the base and or sides of the blocks. When 80% or more of the blocks have signs of roots open the vents on the propagator and leave for two days. After this remove the propagator lid completely and leave for a further 3-4 days under fluorescent light. This process hardens the clones and prepares them for the growing environment.
Stop using the clone solution or bloom nutrient when the roots have fully struck. At this point begin using a quarter strength vegetative solution to encourage foliar growth. Increase the strength of the nutrient as the plants grow.
Growing the Clones out under Fluorescent Light
OK, so you’re clones have struck. Not so hard is it? Problem is now you have a week or more before you can put them into the growing system. What now?
Rule number 1 at this point becomes: exposed roots need to be protected/shielded from light. So, we now need to either put our 40×40 blocks into larger blocks or put a medium such as coco coir into the propagator tray. The roots will grow down into this and ensure a large, healthy root system when your strikings go into the growing system. (C Illustration)
At this point we also need to start feeding our clones with a 1/3 strength vegetative nutrient.
It is also helpful to raise the cuttings up close to the fluorescent light to stimulate growth. Maintain a distance of approx 60mm between the top of the cuttings and the light.
A recent addition to fluorescent plant-based lighting are 100watt plus fluorescent bulbs (e.g. Spectrum 130watt fluorescent Lamps) that are colour balanced specifically for plants. These bulbs (available through all good hydroponic stores) are highly recommended for the early stages of vegetative growth. They have low heat emissions and more than enough lumen output to stimulate prolific foliar growth in the early vegetative stage of the crop cycle. This makes them ideal for growing out the plants in preparation for the flowering cycle. They are also suitable for cloning. Your hydro supplier will be able to advise you further. Illustration below of cloning propagator using heat pad.
Coco Coir Media for Cloning
Other than rockwool there are several mediums that can be used for striking clones. By far our favourite for this is coco coir. Simply place coir in well drained small cups, wet/hydrate the coir with ph 5.5 – 5.8 clone solution (or a 1/3 strength bloom solution) and you are ready to go. Dip your cuttings in a cloning gel, insert your cuttings in the coir and place in propagator. I.e. Coir replaces rockwool as the media.
Coco coir today is perhaps the most commonly used and most popular growing media amongst hobby growers around the world. This in itself speaks volumes about the qualities of coir. Put simply, the consumer has driven the coir revolution because it is a medium that performs consistently time after time after time. Coir has excellent insulation properties (ideal for hot climates), root preservation qualities, pH stability, is organic and has cation exchange properties, meaning minerals are readily available to the root system.
Coir has almost optimum air porosity (oxygen/moisture ratio) which makes it ideal for striking clones. Along with this, coir possesses high levels of potassium, a mineral element that aids root growth, again making coir an ideal medium for striking clones. A further benefit is coirs pH ranges from approximately 5.5 to 6.3 making it ideal as a cloning media (unlike rockwool, no presoaking to achieve optimum pH). In recent years some hydro manufacturers have recognized the values of coir as a cloning media and released coir clone blocks (Eg. Atami B’Cuzz Plugz etc).
Quality of Coir
For cloning purposes it is imperative that you invest in a high quality presoaked and buffered coir product. We recommend Atami B’Cuzz Coir and/or Canna coir because we know these products are first rate. However, there are many brands of presoaked and buffered coir available and your hydro supplier will be able to advise you further. As an absolute rule do not use a cheap compressed coir product – many of the compressed products contain high levels of sodium chloride (common table salt), which is sure to stress and/or kill young plants.
Building a Propagating System
Above is a diagram of a propagating system that you can build yourself. What you will need is a light proof (black etc) plastic tub with a light proof lid. Drill or cut holes to accommodate cups which allow for drainage (Strawberry cups available from your local hydroponic store or nursery supplies are ideal) and use a water heater to maintain a constant optimized temperature. Purchase a propagator lid from your local nursery, hydro supplier or, hardware store etc and you have an ideal propagating system (temperature and humidity optimized).
The advantage of this system over the heat pad system is that it can also be used in the interim as a short-term growing system. No need to place the cuttings into bigger blocks etc. The roots can be grown out into the light proof (dark) tub and the cuttings can be maintained in this system for several weeks under fluorescent light. Due to the oxygenated water and the air gap between the base of the plants and the water/nutrient in the tub there is plenty of oxygen available to the roots of the plant (I.e. roots require plenty of oxygen).
This system is ideal for use with Coco Coir media. Simply fill the cups with coir and add cuttings.