Divide rhubarb plants in early spring or late winter. Since this is the dormant period of the plant, transplanting at this time promotes healthy roots during division and replanting. These plants must be divided every five to 10 years. If the rhubarb has outgrown its current location however, the plant can be divided as early as four years after planting.
Use a spade fork to loosen the ground around the crown of the rhubarb. For easy lifting, loosen the soil to a depth of 8 inches. Ensure that you are working 6 inches away from the crown of the plant so you don't damage the roots. Slide a trowel under the roots, and lift the plant from the soil.
Locate the bud, and cut the crown with a sharp knife to divide the plant. Ensure that each section contains roots and a healthy bud. The new plants only grow after replanting. If you must store the divisions, place them in peat moss, and keep the temperature between 32 and 40 degrees Fahrenheit.
Prepare a new bed with properly draining soil, compost and generous sunlight, and replant the divisions. Space the crowns 3 feet apart, with the bud 1 inch beneath the soil. You can begin harvesting after three years.