Phlox - Brilliancy This is an easy, reliable and free-flowering variety which is reliable whatever the weather. The compact plants are perfect for edging, containers and borders. The half hardy annual reaches the height of 25cm. Sow outdoors from March to May, where they are to flower, 0.5cm deep, directly into finely-prepared, well-drained soil, which has already been watered. Seedlings usually appear in 14-28 days. Thin them to 15cm apart and water well until plants are established. For a continuous display, make sowings at two to three-week intervals. Sowings made in curves, rather than straight lines, often create a more pleasing effect. Flowers from June to October.