Maximizing Tropical Plant Growth in Short Seasons: Soil, Fertilizer, and Water

Reader Question: Pushing Bananas, Cannas, Elephant Ears in Louisville, KY

"I grow bananas, cannas, colocasias outdoors. Season is short. Using Epsom salt + 20-20-20. Want bigger, faster growth. Soil enriched with manure/compost. Water nightly. What fertilizer numbers and rates?"

Expert Answer: You're Already Doing the Critical Things

• Deep, amended organic soil (manure + compost) = #1 factor. You have this.
• Balanced fertilizer (10-10-10, 20-20-20) monthly = excellent.
• Epsom salt = magnesium only; already in complete fertilizers. Use sparingly—it's a salt and can burn.
• Frequent watering = necessary for large-leaf tropicals in heat. Daily may be needed.
• Mulch heavily = conserves moisture, moderates soil temp.

To Push Further

1. Start earlier: Pot up rhizomes/corms in greenhouse 4–6 weeks before last frost.
2. Foliar feed: 20-20-20 at ½ tsp/gal every 2 weeks during peak growth.
3. Wind protection: Shredded leaves = lost photosynthetic area.

You're near the practical limit. Genetics and season length ultimately cap size.