Squash Container Soil Mix
Cucurbita pepo / moschata
Container soil mix for bush and vining squash — pumice-heavy for water efficiency, vermicompost for slow N.
- Container:
- 10-15 gal bush / 20+ gal vining
- pH:
- 6–7
- EC:
- 1.8–2.4 mS/cm
- Sun:
- 6–8 hr
Components
Percentages by volume. Quantities scaled for a 15-gallon container (US units).
| Component | % | Amount |
|---|---|---|
| Quality potting mix Base structure, initial nutrients | 30% | 18 qt |
| Coco coir (low-EC, buffered) CEC, moisture buffering | 25% | 15 qt |
| Pumice Drainage, aeration (lower water requirement)
Alternates: Perlite | 20% | 12 qt |
| Vermicompost / Worm castings Nutrients, microbes, growth hormones | 12% | 7 qt |
| Aged compost Microbial diversity | 8% | 5 qt |
| Charged biochar Long-term CEC, nutrient retention | 5% | 3 qt |
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) 5-5-51.5 cup
- 4.5 tbsp
- 3 tbsp
- Epsom salt3 tbsp
- 3 tbsp
- Mycorrhizae inoculant At root zone.3 tbsp
Growing notes
- Soil must hit 70F before transplant. Cold soil stunts cucurbits permanently.
- Heavy feeder + heavy drinker. Min 1"/week water; side-dress weekly during fruit.
- Hand-pollinate AM if bees are scarce.
- Powdery mildew is the dominant disease pressure; space for airflow.
- Watch for squash bug and vine borer.
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
- Soilless beat soil for zucchini yield; pumice lowest water; cocofibre earliest yield — Rouphael et al. (2004) . J Hort Sci Biotech
- Squash yield dropped 38-58% when nutrient solution halved — Rouphael et al. (2009) . HortScience
- Squash pH 6.0-6.8 optimal (Oklahoma State Extension) — Oklahoma State Extension