Taking cuttings from plants and placing them in a cup of water to grow roots is something that most of us have encountered in the past. You can root cannabis cuttings the very same way if you keep the water from getting anaerobic or swampy. It really is that simple. The fact that many folks spend a fortune to accomplish such a simple task is amazing. Even if you plan to use another method, this is a great way to temporarily store cuttings before rooting.
Uncle Pete usually uses the bottom branches cut off during regular maintenance of larger plants and stores them in labeled nursery pots or Solo cups for an hour or two prior to putting them in the cloner. A dedicated "mother plant" is unnecessary - any plant in vegetative growth can become a mother plant. See the intermediate topic Caring For A Mother Plant for more detail.
Most of the time, gardeners make cuttings from the growing tips of branches, but any cutting from a growing branch will grow roots. However, make sure the cutting has at least three nodes for best results. Depending on your growing and pruning style, you can get a small head start by using these "topped" cuttings.
Cannabis plants grow roots naturally after being cut from the plant - there is only one thing you need to understand about the science behind putting roots on a plant: environment. As always, the importance of environment in growing plants cannot be overstated. For rooting cannabis cuttings, air temperature, water temperature, and light are the parameters to be controlled. The air and water temperature should be kept at 68-75 degrees Fahrenheit, and low-intensity fluorescent light (T8 or T12) is all that is needed.
There are two main methods Uncle Pete uses to root cannabis cuttings:
Directly in a small pot or Solo cup of Pro-Mix with an inverted clear cup on top to trap humidity around the cutting.
In an "aeroponic" cloner with plain water and air bubbles.
Rooting Directly In Pro-Mix
This method is easily accomplished with common household materials - no need to make a large expenditure. Simply take cuttings from the growing branches of your mother plant using a sharp pair of scissors, knife, or razor blade. Many instructors preach that these instruments need to be clean and sterile. Uncle Pete just uses his trim scissors after wiping them on his pants. Do not overthink cloning. It is simple, yet the most belabored part of our process. If you cannot put roots on a clone, you should not attempt to grow cannabis indoors. It is that simple.
Dip the bottom 1/2" of the cutting stem in rooting powder or rooting gel if you have any. It is not required. Aloe gel directly from the plant works well - don't use aloe gel bought in a store as it contains additives that can impair rooting.
Stick the cutting down into the cup of Pro-Mix (about two inches) and gently press the dirt down around the stem to firm it into place while being careful not to fold the stem. If you damage the stem discard the cutting, as the chances of successful rooting are greatly reduced.
If you are using a Solo cup rather than a small plant pot, cut two holes (approx 1/4") in the bottom of the cup on either side to allow water drainage.
Thoroughly soak the Pro-Mix with plain water.
Invert a clear cup on top of the cutting and place under low-intensity fluorescent light.
Water the cutting again only after it dries out a bit, but don't let it dry out completely.
Rooting In A Cloning MachineThe "aeroponic" cloner method is even simpler: take cuttings from the mother plant and put them in a cloning machine full of water under low-intensity fluorescent light, according to the manufacturer's manual. The EZ-Clone is a reliable and proven design that will churn out clones for years. If you are handy, there are dozens of creative designs to be found on the internet which will accomplish the same task.
When the clones have a nice set of roots on them, plant them directly into a 1 gallon or 2 gallon container filled with Pro-Mix. These "aeroponic" clones will grow in the Pro-Mix the same as clones we rooted in cups above - ready for vegetative growth under 24 hours of high-intensity fluorescent light (T5 HO).