How To Grow Phlox From Seed

August 26, 2022

Phlox or Drummond's Phlox it's easy to grow and maintain, and once established, it has a fairly good tolerance to drought.

Phlox is a low-growing ground cover, featuring many branches and 5-petal flowers on the terminal spikes. The flowers have separate petals, and a few specimens have ragged-edged petals. Most phlox share the same range in bloom colors, including magenta, pink, lavender, white, or peach. However, some cultivars are blue or purple. The blooms in some varieties are bi-colored, and most have a degree of shading.

Drummond's Phlox may be grown in full sun or partial shade. The plants will produce more flowers when they are grown in full sun.

Phlox likes well-drained sandy soil, but also do well in poor to medium soil with good drainage.

The annual phlox dislikes root disturbance. Therefore, sow Phlox flower seeds directly outdoors into prepared soil in the late fall or spring. Scatter the flower seed evenly, rake into loosened topsoil to provide a good seed contact with the soil and cover lightly with 1/8″ of fine garden or potting soil. Water thoroughly once.

Be sure to keep your planting beds consistently moist with a mist sprayer or gentle hose setting while the seeds sprout. Once the plants have grown a few pairs of true leaves, you can scale back watering unless the phlox variety requires otherwise.

The small seeds will germinate at 16°-18°C (60°-65°F). Thin or space transplants at 20-30cm (8-12") apart.

For an abundant display the following year, allow Phlox Drummondii to re-seed.

Phlox germinate and grow quickly, so in most cases you're best off direct-sowing your seeds.

But, if springtime is late in your area, start them indoors 4-6 weeks before the potential last frost.

Scatter seeds evenly over the soil and cover them with 1/8" fine soil. Darkness is required for germination. Then carefully transplant outdoors when the first true leaves appear. Seeds should germinate in 5-10 days.

Seed Treatment: None required.
When to Plant Outdoors: As soon as the soil is consistently 65°F to 70°F.
When to Plant Indoors: 6 to 8 weeks prior to last spring frost.
Seed Depth: ⅛"; some sunlight required to germinate.
Seed Spacing: Plant or thin 1' apart in dryer conditions; 2' in humid regions or when planting in consistently-irrigated beds.
Days to Germination: 5 to 10 days at 70°F; 7 to 14 days at 65°F.
Transplanting Tips: Harden off for a few days prior to transplanting. If using biodegradable pots, score and moisten before placing the entire container into the bed or pot.

Add a general-purpose fertilizer when planting them, then once a month after that.

Drummond's Phlox is a cool season plant, so it may slow down in the heat of high summer. If this happens, cut the plants back dramatically to just 5cm (2"), and await a second burst of blooms as autumn approaches. Be sure to keep irrigated in hot weather, especially in containers.

Mulching will help retain moisture and moderate soil temperatures, but be sure to keep mulch away from the plant stems. At the end of the season, cut back annual phlox to soil level. Cut perennial phlox 2" above the soil level, and clean up any debris; it will regrow again in the spring.

Hardy annual Phlox varieties often survive the first few light touches of frost. However, they will not survive a hard frost or freeze. Perennial Phlox varieties go dormant after a killing frost, until next spring. At this time, it is recommended to cut the plants down to the ground.

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