How to Plant Garden Phlox

Plant garden phlox divisions with the crown about 1½ inches below the soil, 18 inches apart, in full sun and with good air flow to keep powdery mildew away.

How to Plant Garden Phlox
When to plant
Spring, or late summer to early fall at least 4–6 weeks before the ground freezes
Depth
Crown about 1½ inches below the soil surface
Spacing
18 inches apart
Sun
Full sun, at least 6 hours; tolerates light shade
Water
Water thoroughly and regularly, at the soil, not over the leaves
Soil
Moderately fertile, moist but well-drained, rich in organic matter

Step by step

  1. Choose a sunny, open spot where air moves freely around the plants.
  2. Work plenty of compost into the soil, especially on sandy ground.
  3. Set each division with its crown about 1½ inches below the soil surface.
  4. Space plants 18 inches apart for good air circulation.
  5. Firm the soil and water thoroughly.
  6. Water at the base of the plant rather than over the leaves; wet foliage invites mildew.
  7. In mid to late June, once the soil has warmed, spread 2–3 inches of mulch to keep the roots cool and moist.

After bloom

Deadhead faded flower clusters for rebloom and to stop self-sown seedlings, which usually come up a different color. After the first fall frost, cut plants back to 2 inches above the ground and clear away old stems and debris to limit mildew next year. Feed lightly with 10-10-10 as new growth emerges in spring and again just before flowering. Divide every 2–4 years, ideally in spring.
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