How to Propagate Phlox
Native to North America, phlox can be either an annual or a perennial flowering plant. They adapt to a wide variety of habitats and are easy to propagate and grow. Propagation is usually via cuttings or root division. The best time to dig up phlox clumps is in spring, before new growth begins. With cuttings, start indoors six to eight weeks before the last frost so that you can plant your phlox by spring. Phlox is hardy to USDA zones 3, 4, 8 or 9, depending on the variety.
Cut a 4-inch stem from the phlox. Choose a stem that has no flower buds. Remove the lower leaves.
Pour the sand into the planting pot and water it well. Stir the sand to make sure it is uniformly moistened. Allow the excess water to drain from the bottom.
Poke the phlox stem into the sand and tamp around the base to ensure good contact with the sand.
Place the potted cutting in an area that receives a lot of light but no direct sun. Your cutting should root in six weeks.
Transplant phlox into your garden after the last frost date for your area. If you are planting more than one, space them 8 to 10 inches apart.
Prepare the planting area by digging up the soil to a depth of 6 inches, turning the soil and breaking up any large clods.
Dig the phlox clump, with roots attached, from the garden. Find a clump with at least three shoots.
Dig a hole in the planting area so that the top of the clump, where the shoots begin, will be 1 inch below the surface of the soil. Cover with soil and tamp lightly. If planting more than one clump, space them 18 inches apart.
Water the area well and keep the soil moist but not soggy.
Cut all but five stems from the new plant once it has grown to 6 inches in height. Pinch the tips of the remaining stems. This will encourage the phlox to produce larger flower clusters.
Choose a spot in your garden that gets lots of sunshine.