Trim the vine to a height of 6 to 12 inches, using sharp pruning shears. Make cuts just above a leaf node, which is the small bump on the stem where leaves emerge.
Dig around the root zone with a sharp spade.
Work the spade beneath the roots carefully, until they are loose enough to be easily lifted from the ground.
Grasp the vine at the base of the stem, near the roots, and remove it from the soil.
Cut the roots into clumps with a sharp knife. Make certain that each divided clump contains a minimum of two shoots and a 3- to 4-inch portion of the roots.
Replant the newly divided sweet autumn glory clematis immediately to keep the roots from drying out. Water until the soil feels very moist.