How to Grow Water Pepper
Persicaria hydropiper
Water pepper is an unusual herb that prefers moist, even wet soil and tolerates partial shade — the opposite of most culinary herbs. Sow indoors in spring or direct-sow once soil reaches 10°C, keeping the seedbed consistently moist. Transplant to a pond margin, bog garden, or any reliably damp spot after last frost. It grows quickly to 30-70 cm and produces peppery, spicy-tasting leaves used in Japanese cuisine (as "tade" with sashimi) and across Asian cooking. Harvest leaves frequently before flowering for the strongest flavour. Add raw or at the end of cooking — heat destroys the peppery compounds. Plants self-seed freely; allow a few to set seed for next year.
When to Start
Sow indoors 4 weeks before last frost, or direct sow outdoors after frost risk has passed and soil reaches 10°C.
Don't know your frost date? Find it here →
Growth Stages
Approximate days from start
Care Essentials
- Light feed at planting only. Growing in moist, fertile soil usually provides enough nutrition. Avoid heavy nitrogen feeding — it reduces the peppery flavour.
- Water pepper thrives in moist to wet soil and partial shade, unlike most herbs. It self-seeds freely and can naturalise at pond margins or boggy areas. The peppery bite fades quickly with heat — add leaves raw or at the very end of cooking.
Growing Conditions
- Min. soil temperature
- 10°C+
- Germination temperature
- 10–20°C
Enter your last frost date to see your dates
- Sow indoors
- —
- Transplant out
- —
- First harvest
- —
Want your full season plan with reminders? Try Leaftide free
Spacing & Planting
| Plant spacing | 20 cm |
| Row spacing | 30 cm |
| Sow depth | 0 cm |
| Mature height | 60 cm |
| Mature spread | 25 cm |
Growing Conditions
| Min. soil temperature | 10°C |
| Germination temperature | 10–20°C |
| Base growth temperature | 5°C |
| Photoperiod sensitivity | day neutral |
Frequently Asked Questions
- How far apart should I plant Water Pepper?
- Plant Water Pepper 20cm apart with 30cm between rows.
- When can I harvest Water Pepper?
- Water Pepper is ready to harvest approximately 50 days after transplanting.
- Is Water Pepper frost hardy?
- Water Pepper is classified as Half Hardy.
