The customary direction to propagate creeping phlox through root ball divisions is to dig up the established plant in early spring. A creeping phlox may be established in as little as two years, but three to four years in the ground will show a more robust root ball. 'Blue Emerald' variety of creeping phlox is shown above.
Full root ball removal
Lift the spreading portion of the plant to locate the center of the original plant. Use a shovel to dig a circle about 6 inches out and around the plant. Push the shovel underneath the plant the depth of the shovel blade to free it from the soil. Lift the root ball from the ground. Use your fingers (or a knife for dense root balls) to separate the root ball in half. Divide each of the halves into two or three sections and then replant each section. The root ball of creeping phlox can be divided in spring or fall.
Partial root ball removal
If your desire is to leave the main plant but grasp part of the root ball to enlarge the coverage area of creeping phlox, then you do not have to dig up the entire root ball. In the picture above, on the right is the initial creeping phlox planted two years earlier. Looking again at the picture above, the medium size plant on the left and the small plant on the lower left are both self-established from the initial plant on the right as it spread (or trailed). As the stems of a creeping phlox grow, the weight of the stem forces it to the soil where it will root.
What I did, because I wanted some starts off the initial phlox plant, was to use a spade to disconnect the recent growth. To do that, I forced the spade straight down between the small plant and initial plant, and about 2 inches from the small plant. The spade breaks through the roots. I was then able to scoop up a small root ball suitable for immediate re-planting.
How to plant creeping phlox
|Creeping phlox in mid-spring|