Propagate phlox plants by dividing them in early spring. Dig your phlox plant out of the ground and split it into smaller clumps using a sharp knife. Then replant these clumps. You can also direct sow seeds in spring as soon as the ground can be worked. Cover seeds lightly with 1/8 inch of soil. Germination should occur in 5 to 10 days.

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.