When to plant Phlox in Temperate Australia
Temperate zone — applies to Sydney, Melbourne, Adelaide, Perth, Newcastle and similar areas. Growing elsewhere? Cool · Subtropical · Tropical · Arid.
Sow annual phlox direct from August to December, once frost risk is easing, covering the seed lightly at 3 mm. Germination takes 10–20 days and the seed prefers darkness, so cover it fully and keep the bed just moist. Plants flower quickly in around 70 days, making phlox one of the faster annuals for temperate colour. Space or thin seedlings 10–15 cm apart with 20–30 cm between rows in full sun. In Melbourne and Adelaide gardens a spring sowing gives a bright, low display through late spring and summer.
Sowing calendar — temperate zone
Green months are your sowing window: August to December.
Growing notes
Annual phlox is a hardy, fast, low-growing flower that fills the front of temperate borders with dense colour. Sow it direct from late winter through spring, and because it flowers in about 70 days you can make a couple of sowings to stretch the display across the season. Full sun and free-draining soil suit it best.
Germination is the step to get right. The seed wants darkness, so cover it fully at 3 mm and keep the surface evenly moist but not wet until seedlings emerge over 10–20 days. Sowing too shallow, so the seed sits in the light, or letting the bed dry out gives the patchy strike that frustrates most first attempts.
Once up, phlox is easy. Thin seedlings to 10–15 cm so plants have room and airflow, since crowded stands are more prone to powdery mildew in warm, humid weather around cities like Sydney. Water at the base, not overhead, and remove any mildewed leaves. Deadhead or shear spent flowers lightly to encourage a second flush. In hot summers plants may fade early, so a follow-up sowing keeps fresh colour coming. Phlox also makes a good, long-lasting cut flower for small posies.
Phlox at a glance
| Sowing depth | 3 mm |
|---|---|
| Plant spacing | 10-15 cm |
| Row spacing | 20-30 cm |
| Germination | 10-20 days |
| Days to maturity | 70 days |
| Frost tolerance | Hardy |
| Method | Raise Seedlings,Sow Direct |
Common questions
- when do you sow annual phlox in temperate Australia
- Sow direct from August to December once frost risk eases. Phlox flowers fast, in about 70 days, so a spring sowing gives colour through late spring and summer. Successive sowings extend the display.
- does phlox seed need light or dark to germinate
- Annual phlox prefers darkness, so cover the seed fully at about 3 mm and keep it moist. Leaving seed uncovered in the light is a common reason for patchy germination over its 10–20 day window.
- how far apart do you space phlox plants
- Thin or space plants 10–15 cm apart with 20–30 cm between rows. Adequate spacing improves airflow and reduces the risk of powdery mildew in warm, humid weather.
- how do you stop powdery mildew on phlox
- Space plants well, water at the base rather than overhead, and remove affected leaves. Crowded, humid conditions encourage mildew, so good airflow is the main defence in coastal temperate gardens.
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