Fertilizing Greenhouse Plants: Timing, Types, and Techniques

Greenhouse fertilization requires precision—matching nutrients to crop, stage, and growing method.

General Principles

• Newly potted plants need time to root before fertilizing.
• Crop-specific nutrient needs are non-negotiable.
• Houseplants: fertilize every 1–2 months in growth, 1–2× in winter. Liquid at half-strength more frequently.
• Annuals: every 2 weeks in short season. Azaleas: no fertilizer during bloom.

Fertilizer Selection

• Most greenhouse fertilizers: ~50% nitrogen, nitrate-based, labeled "peat-lite." Check N-P-K on bag.
• Standard application: 200 ppm nitrogen (e.g., 21-5-20 or 20-10-20) via constant liquid feed. Adjust for crop.
• Balanced growth: N-P-K near 1-2-1 for flowering/foliar plants.
• Soluble > slow-release for speed and control.

Application Rules

• Soil must be moist—dry roots burn from chemical concentration.
• Always use recommended dilution or weaker—strong solutions damage tender roots.
• Use injectors/siphons with backflow preventers to protect water supply.
• Avoid softened water (high salt).

Recommended Systems

• Flora series (Floramicro, Florabloom, Floragro): mix ratios for any crop/stage.
• Calcium Nitrate (greenhouse grade) + Hydro-Gro for large-scale complete nutrition. Buy 50-lb bags for economy.

Daily monitoring catches pests/diseases early. Know each plant's habits. Enjoy the greenhouse journey!