Usually, a few weeks before the sprouts would normally emerge, you dig up small clumps of 3-4 stems, with as many of the attached rhizomes and roots as you can manage. Immediately prune the tops of the division back enough to remove 1/2 to 2/3 of the leaves. Soak the roots in a solution of 1 ml white vinegar and 3 ml of seaweed extract for every 4 liters of water, while you prepare their new home, hopefully no more than a few hours. Plant them no deeper than they were originally, and use a stake to hold them up.

For more, but smaller, babies, cut the thickest stems at the base. Cut those stems into sections 3-4 joints long. With a metal rod, break out the top few walls between joints, leaving the bottom one intact. Plant the sections bottom side down, just deep enough to hold them up, and keep the insides full of rainwater or purified water. Tap water or river water will do if it isn't too hard, salty, or polluted. After a few weeks, little leafy sprouts will come out from the upper joints, and the buried joint will grow little new rhizomes and roots. Usually about a 75% success rate, unless something goes wrong! After 2-3 years, each new plant will be as big as a 1 year old division.

Hope this helps! : )