When & Where to Plant Phlox
Phlox can be planted in spring or fall, and should be planted immediately upon receiving.
Light: Both varieties of phlox enjoy full sun, although the upright Garden phlox can take a little afternoon shade, particularly in the south.
Soil: Phlox is tolerant of most garden soils, but well-drained soil is preferable, particularly in northern areas where spring snow is slow to drain. Damp, waterlogged spring soil can rot the dormant roots. Add compost or peat moss to the garden to improve drainage and create a better overall environment.
Spacing: Garden phlox should be planted about 18 inches apart, while Creeping phlox should be planted about 2 feet apart. Giving these plants lots of room for air circulation is the key to limiting the appearance of mildew. (Although most varieties available today have been bred to resist mildew.)
Over the next few years you’ll see that both varieties form clumps that will gradually increase and join together to form one large grouping of phlox, with the Creeping variety creating a mat or carpet.
Planting in Fall: Fall plants can be kept cool on the deck for a few days until it’s convenient for you to plant, but don’t let the roots dry out and be sure to plant a few weeks before your first frost arrives.
Planting in Spring: Likewise, if the plant arrives in a container in spring, keep the container moist until the ground is ready to plant. Hold off on spring planting until the soil is free from melted snow and ice, and the ground is easy to work.