Greenhouses create a unique irrigation challenge—higher temperatures, no rainfall, dense plant spacing, and the need for precise moisture control. Drip irrigation is the ideal solution for greenhouse growing, and I’ve installed systems ranging from small 6×8 hobby greenhouses to commercial 3,000 sq ft operations. The key differences from outdoor drip systems are higher humidity management, fertigation integration, and tighter emitter spacing. Here’s my complete guide to greenhouse drip irrigation.
What Drip System Works Best in a Greenhouse?
For greenhouse benches and tables, use ¼-inch micro tubing with individual adjustable drip stakes at each plant pot. Cost: $0.50-1.00 per plant. For greenhouse ground beds, use ½-inch drip tubing with 0.5 GPH pressure-compensating emitters spaced 12 inches apart. Cost: $0.35-0.50 per foot. For propagation and seedling areas, use fine mist micro-sprinklers or foggers on ¼-inch lines (0.5-2 GPH each). Most greenhouse drip systems operate at 15-25 PSI—use a pressure regulator with a gauge ($15-25). A 150-mesh disc filter is essential for greenhouses using rainwater collection, which is common in greenhouse operations. For basic drip design concepts, start with my drip irrigation guide.
How Do You Design Drip Layout for Greenhouse Beds?
Greenhouse beds are typically arranged in long, narrow rows. Run a ½-inch main header line along the greenhouse spine, then branch into ¼-inch micro lines for each row or bench. Space emitters 6-12 inches apart for dense plantings like lettuce, herbs, or starts. For larger greenhouse plants like tomatoes, peppers, or cucumbers, space 12-18 inches with 1 GPH emitters. I recommend separate zones for benches vs ground beds—benches dry out faster and need shorter, more frequent cycles (10-15 minutes daily) while ground beds run longer (20-30 minutes every 2-3 days). A dual-zone timer ($30-60) handles both schedules. For more on zone planning, my irrigation design guide covers layout strategies.
How Do You Prevent Algae and Disease in Greenhouse Drip Systems?
Greenhouses have higher humidity, which promotes algae growth inside drip lines and on soil surfaces. Use opaque (black) drip tubing—clear or translucent tubing promotes algae growth inside the line. Install a backflow preventer ($15-30) at the water source—it’s required by code in most areas for greenhouse irrigation to prevent fertilizer or algae from contaminating the water supply. Flush greenhouse drip lines monthly (more often than outdoor systems) to prevent algae buildup. Use a 150-mesh filter and clean it every 2 weeks during peak growing season. For fertigation through greenhouse drip, check my fertigation guide for injector setup and cleaning.
How Much Water Do Greenhouse Plants Need?
Greenhouse plants typically need 0.5-1.5 inches of water per week—less than outdoor plants because there’s no rainfall contribution and lower wind evaporation. But the frequency is higher: in summer, greenhouse beds need watering every 1-2 days, and benches may need daily watering. Run drip cycles for 10-15 minutes on benches and 20-30 minutes on ground beds. A humidity sensor ($25-50) or electronic moisture meter helps dial in the schedule. In winter, reduce watering by 50-75%—greenhouse plants grow slower and use less water in low-light conditions. For timer programming, my timer guide covers greenhouse-specific scheduling.
How Much Does a Greenhouse Drip System Cost?
For a 10×12 hobby greenhouse with 200 sq ft of bench space: $30-40 for 100 ft of ½-inch header tubing, $25-40 for 50 adjustable drip stakes with ¼-inch micro tubing, $15-25 for a pressure regulator with gauge, $12-20 for a 150-mesh disc filter, $10-15 for backflow preventer, and $25-40 for a dual-zone timer. Total: $117-180. For a 500 sq ft greenhouse with ground beds: expect $200-350. The system pays for itself in reduced water waste (greenhouse drip uses 40-60% less water than hand watering) and improved plant health. For a full cost comparison, see irrigation system costs.
References
- Extension Foundation: Greenhouse Irrigation Systems — Research-based guidelines for designing drip irrigation systems in greenhouse environments for optimal plant growth.
- Irrigation Association — Greenhouse Micro-Irrigation Standards — Industry specifications for drip system components and layouts in controlled environment agriculture.
- EPA WaterSense: Greenhouse Water Efficiency — Official recommendations for water-efficient irrigation practices in greenhouse operations including drip and micro-spray systems.