How to Grow Annual Phlox
Phlox drummondii
Annual phlox is a half-hardy annual for full sun and well-drained soil. Sow indoors 6 weeks before the last frost at 15-18°C, covering seeds lightly as they need darkness to germinate. Prick out into modules, harden off, and plant out 25cm apart from mid-spring. Keep deadheading spent clusters to extend the flowering season from late spring well into autumn. Plants flower best in cool conditions and may slow in midsummer heat before picking up again.
When to Start
Sow indoors 6 weeks before last frost, or direct sow outdoors after frost risk has passed and soil reaches 10°C.
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Growth Stages
Approximate days from start
Care Essentials
- Feed every two to three weeks with a balanced or high-potash liquid fertilizer once flowering begins.
- One of the easiest hardy annuals from seed. Flowers best in the cool of spring and early summer; may pause in peak heat but resumes in autumn. Excellent for cutting.
Growing Conditions
- Min. soil temperature
- 10°C+
- Germination temperature
- 15–18°C
Pet Safety
- Sow indoors
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- Transplant out
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- First harvest
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Spacing & Planting
| Plant spacing | 25 cm |
| Row spacing | 25 cm |
| Sow depth | 0.3 cm |
| Mature height | 35 cm |
| Mature spread | 25 cm |
Growing Conditions
| Min. soil temperature | 10°C |
| Germination temperature | 15–18°C |
| Base growth temperature | 5°C |
| Min. daylength to start | 10h |
| Photoperiod sensitivity | day neutral |
Frequently Asked Questions
- How far apart should I plant Annual Phlox?
- Plant Annual Phlox 25cm apart with 25cm between rows.
- When does Annual Phlox flower?
- Annual Phlox typically flowers approximately 35 days after transplanting.
- Is Annual Phlox frost hardy?
- Annual Phlox is classified as Half Hardy.
