Roselle Container Soil Mix
Hibiscus sabdariffa
Container soil mix for roselle (Hibiscus sabdariffa) — sandy-loam-mimicking, biochar-enhanced for salinity tolerance.
- Container:
- 7-10 gal
- pH:
- 5.5–6.8
- EC:
- 1–2 mS/cm
- Sun:
- 6–8 hr
Components
Percentages by volume. Quantities scaled for a 7-gallon container (US units).
| Component | % | Amount |
|---|---|---|
| Quality potting mix Base structure, initial nutrients | 30% | 8.5 qt |
| Coarse sand Mimics native sandy loam, drainage
Alternates: Pumice | 20% | 5.5 qt |
| Coco coir (low-EC, buffered) CEC, moisture buffering | 20% | 5.5 qt |
| Aged compost Microbial diversity | 15% | 4 qt |
| Vermicompost / Worm castings Nutrients, microbes, growth hormones | 8% | 2 qt |
| Charged biochar Long-term CEC, nutrient retention | 5% | 1.5 qt |
| Perlite Drainage, aeration | 2% | 2.25 cup |
Per-container amendments
Scaled linearly to your container size. Apply at transplant or as side-dress per the notes on each line.
- Balanced organic fertilizer (4-4-4 / 5-5-5) 4-4-4 or 5-5-50.5 cup
- 1 tbsp
- Basalt rock dust or azomite2 tbsp
- 1 tbsp
- Mycorrhizae inoculant At root zone.1 tbsp
Growing notes
- Short-day plant — won't flower until day length drops below ~12.5 hours.
- Transplant 5-6 months before first frost.
- Highly salt-tolerant; biochar + compost boost performance further.
- Susceptible to root-knot nematode — rotate yearly.
- Stake at maturity (top-heavy, 4-7 ft).
Want to scale this to a different container size, save it to a plot plant, or track applied dates? Open it in the interactive calculator.
References
- Roselle culture: pH 5.5-6.8, organic matter >1% — Rutgers NJAES . Rutgers NJAES Fact Sheet FS1298
- Biochar + compost (1% each w/w) increased N+16%, P+38%, K+15%; anthocyanin +29% — Liu et al. (2021) . Scientific Reports
- Rice husk biochar on roselle: height +16.5%, stem +12.0%, leaf area +12.9% — MDPI study (2025) . MDPI