Phlox subulata, commonly known as creeping phlox, is a popular, low-growing perennial groundcover. This plant forms a carpet of color, typically in shades of pink, purple, or white, during the early spring season. Dividing creeping phlox is a straightforward and effective horticultural practice used for both propagation and maintaining the plant’s long-term health. The process allows gardeners to create new plants while simultaneously rejuvenating older, less vigorous clumps.
Why and When to Divide Creeping Phlox
Division serves two primary purposes: rejuvenation and propagation. Over time, established clumps of Phlox subulata can become woody or sparse, often showing deterioration or dead spots in the center. Dividing the plant removes the older, less productive central section and encourages new, healthy growth in the replanted divisions, refreshing the parent plant.
The second reason is to generate new plants from a mature specimen, which is an easy way to expand coverage of this groundcover. Timing is important for success. The optimal window for dividing creeping phlox is immediately following its spring flowering period, typically in late spring or early summer, or during the early fall season.
Dividing after blooming ensures maximum time for divisions to establish roots before extreme weather. Avoiding the heat of mid-summer is important, as high temperatures stress vulnerable root systems. A fall division must occur at least four to six weeks before the first hard frost, allowing the roots to anchor firmly before the ground freezes.
Essential Tools and Preparation
Gathering the correct tools before beginning the division minimizes stress on the plants. A sharp, clean spade or garden fork is necessary for lifting the main clump from the soil. For separating smaller sections or cutting through woody parts, have a sharp, sterile utility knife or pruners ready.
Proper preparation of the mother plant ensures the root ball is manageable and hydrated. Thoroughly watering the phlox the day before division saturates the soil, helping the root ball stay intact and reducing transplant shock. Focus on lifting areas with healthy, vigorous growth on the outer edges for the best propagation material.
The new planting site should be prepared ahead of time to minimize the time divisions spend out of the ground. Loosening the soil and incorporating organic material, such as compost, creates an optimal environment for new roots to establish quickly. This preparation is a small step that increases the overall success rate of the transplanted divisions.
The Step-by-Step Division Process
Starting the division process often involves a light pruning of the foliage on the mother plant, which is an optional step but can reduce moisture loss after transplanting. Using your spade or garden fork, carefully dig around the perimeter of the clump you wish to divide. Work several inches away from the stems to ensure you capture a healthy root system.
Once the section is loosened, gently lift the entire piece from the ground, keeping the root ball as intact as possible. Separate the lifted clump into smaller, viable divisions. Due to the plant’s mat-forming habit, sections of the root mass can often be gently pulled apart by hand.
If the center of the clump is dense or woody, use your sharp, sterile knife to cut through the root mass. Each resulting division must contain a healthy portion of foliage and sufficient active roots to support new growth. Discard any central sections that appear dead, woody, or overly sparse, keeping only the younger, more vigorous outer sections.
Replanting and Immediate Care for Divisions
The newly separated divisions should be planted immediately in their prepared location to prevent the roots from drying out. Select a site that offers well-drained soil and receives full sun, mimicking the ideal conditions of the parent plant. Dig a hole for each division that is wide enough to accommodate the spread of the roots.
Place the division into the hole so that the crown—the point where the stems meet the roots—is level with the surrounding soil surface. Avoid planting too deeply or too shallowly. After setting the division, backfill the hole with soil, gently firming it around the roots to eliminate air pockets.
Immediate and consistent hydration is necessary for the survival of the new plants. Water the divisions thoroughly immediately after planting to settle the soil around the roots and begin the establishment phase. For the next several weeks, maintain consistently moist soil, especially as the divisions put out new roots. This dedicated watering regimen is important in helping the new creeping phlox divisions successfully establish themselves and prepare for future blooms.