You can start cloning whenever you want. But it is better to wait until a plant has reached full maturity. Usually, clone when the plant is ready to bloom. This way, I get more clones. However, wait until a mother plant has at least six knots before taking cuttings. Clones need at least two sets of leaves after they are rooted. By waiting for at least six nodes (the point where a leaf comes out of the stem), you’ll have enough material to take clones and still have plenty of growth left on your mother plant.