Marijuana / cannabis cloning is a great way to continue growing the same strain for years without having to make seeds. However, it is also possibly the most difficult aspect of growing marijuana. Cutting pieces of the plant off and then getting those pieces to grow roots is usually the trickiest part for most people. There are a 2 basic types of cloning processes, aeroponic cloning or putting the cuttings in a medium such as rockwool or peat moss pellets. Whatever method you decide to use, making clones really comes down to providing the cuttings with the right humidity, temperature and light. Having tried all the different methods I still prefer the old school method of putting cuttings in peat moss pellets. Below, I explain my technique for making clones in peat moss pellets but it can easily be applied to rockwool cubes.
The first thing you need is a container to put the clones in. The clippings you take should be about 4" to 6" tall and you want a container that is only a couple inches taller than the clippings. It's important to use a container that is not only no more than a couple inches taller than the clones but also one that is just large enough to hold however many clones you are going to put in it. The idea being that you want to have a high humidity level in the container, so the more "packed" it is with clones, the higher the humidity will be. You want a container with a clear lid, otherwise take a clear piece of plastic and tape it to the top of the container. I use dish pans that are about 16" long by 12" deep and 7" tall and I tape a piece of clear plastic on it for a lid. You don't need an airtight seal on the container but you do want it to be tight enough that condensation builds up on the underside of the lid / piece of plastic.
You will need a container to keep the clones in, scissors, a cup of cold water, rooting powder, toothpicks, and peat moss pellets.
The "How To" Part
First decide how many clones you're going to make and put that number of peat pellets in the container / tray. Then take a gallon of water and add some nutrients, you want to use nutrients for the vegetative / grow stage not bloom nutes. For clones I use nutrients at 1/4th of the recommended dosage on the bottle. After you add your nutrients to the water bring your water to about 6.3 ph using ph up or ph down. Now that you have your nutrient water made and ph balanced, fill your clone container with a couple inches of water and put the peat pellets in there. After about 5 minutes the peat pellets will have absorbed all of the water that they are going to. Pour the remaining water out of the clone container. Now take a clipping from the marijuana plant you're making clones of. Take a piece that is about 4"- 6" and has at least 2 pairs of fully developed leaves but no more than 4 pairs. Now take the clipping and make about a 50 degree angle cut at the end of the stalk. Dip the stalk about 1" into the cup of cold water then dip it into the cloning powder about an 1" deep. Now that the bottom 1" of the clipping is coated with the cloning powder take a toothpick and make a hole in one of the peat pellets just large enough to put the clipping in. (peat pellets usually have a hole in them already but the whole is usually too large so it's better to make your own hole with a toothpick) Put the clipping in the hole, place your newly made clone in the clone container and grab another peat pellet and repeat the process until you've made as many clones as you wanted to make. Cover the container with a clear piece of plastic or a clear lid. Place the container so that the lid is 4" under a standard shop light with 40 watt cool white bulbs. You don't need special plant bulbs or special lights for making clones. Keep the container at about 72 - 78 degrees, the inside of the container should be about 76 - 80 degrees. Every day lift a corner of the lid of the container and blow fresh air into it. In about 10 - 14 days you should start to see white roots poking out of the peat pellets. Once you start to see white roots the cannabis clone is ready to plant in a pot.
* It's best not to use a light that is more than 100 watts for cloning.
* After you're clone has started to root and been potted, be carefull not to give it too much food during the first 2 weeks. It's real easy to overdose a clone on nitrogen in the first couple weeks. When you've overdosed your clone it's growth will seem stunted and the stalk may be brown or purple. If you end up with a stunted plant the best thing to do is pitch it and make another clone. If you really need it to survive, the best thing to do is put it in a slightly larger pot and only give it 1/8 the recommended dosage of nutrients untill you see it start to grow again. Then you can gradually up the nutrients.
* Until you get really good at making clones, you should make almost twice as many as you need. This way you can keep the best ones and discard the crappy ones.
* If you're making clones from more than one marijuana plant, you should clean your scissors or trimmers with a paper towel or cotton ball dampened with alcohol. This will help keep from spreading any diseases or pm from plant to plant.
* You should use the same plant for making clones with. When you keep a plant in the vegetative stage for a long time for the purpose of making clones, this is called a "mother plant". You should not make clones of clones. When you make clones of clones you will eventually start to see a loss of growth vigor and general vitality. You also run a larger risk of spreading a plant disease when you clone clones. Usually you will not notice any loss of vigor and vitality until about the 15th generation, meaning if you keep cloning your clones instead of keeping a mother plant, you will start to notice some degradation around the 15th time.
* There is a noticable difference in growth when comparing a marijuana plant grown from seed to a clone. There is a slight noticable difference between a 1st generation clone and a 3rd or 4th generation clone. After the 3rd or 4th generation you probably won't notice any difference in growth until you get to around 12 generations.
* Making clones is the least replicable part of the process of growing marijuana. What works for one person doesn't always work for the next person.
* Clones like a lower ph level than a more mature cannabis plant. If you are cloning in a medium such as rockwool or any other medium that does not contain anything that effects the ph, you should use a ph of about 5.5 . This would also apply to aeroponic cloning. If you are cloning in peat pellets you should use a higher ph (around 6.3) because peat moss lowers the ph. Sphagnum peat moss (the most commonly used commercially) has a ph of about 4.5 - 5.