Monster Cropping is unique amongst training techniques in that it does not affect the plants you are currently growing. Rather, this technique involves taking clones from a mature plant during its flowering stage, producing offspring with numerous heads.
When you take a clone from a flowering marijuana plant and revert it to veg, you end up with an extremely bushy plant with profuse branching and tons of nodes. It is possible to use this phenomenon to your advantage to create plants with lots of heads, giving you great yields.
Another great advantage of Monster Cropping is that it avoids the need to keep mother plants. By taking your cuttings during flowering you can create new clones every generation. You can put all your plants into flower, then take the next generation of clones from them. No need for a separate mother plant taking up precious space in your grow room.