Understanding Greenhouse Maintenance
Maintaining your greenhouse is key to ensuring it operates efficiently, maintains its structural integrity, and provides crops with an environment where they will thrive. Not only will greenhouse maintenance make your greenhouse last longer and perform more efficiently, but it will also help your crops be successful and help prevent pests and pathogens.
Greenhouses can suffer at the hands of severe weather. They are especially susceptible because they are built to provide maximum exposure to light by minimizing the profile of framing. Glazing can be torn and frames can be bent from extreme weather exposure. Buildings that meet the standards of the International Building Code will be better prepared to resist storm damage.
Wind Damage Prevention
- Keep site clear of loose objects
- Clear the site of any dry or weak tree limbs and dead trees
- During severe winds, close all openings to the greenhouse (vents, shutters, doors)
- During severe winds, disconnect the arm to the ventilation motors, tape shutters closed, and turn on exhaust fans to create a vacuum in the greenhouse that will keep the glazing plastic tight against the frame.
Snow Damage Prevention
- Plastic glazing should be tight and inflated to 0.25-inch water pressure
- Retract shade screens so heat can fully reach the glazing
- Consider a standby generator to ensure heating isn’t lost in power outages
Cleaning and disinfection prevent greenhouse problems such as pests and pathogens like Pythium (root rot), algae, gnats, flies, and fungus. Cleaning is especially important in-between crop cycles when the greenhouse is empty. Algae is a breeding ground and food source for gnats and flies. It can grow in walkways, water pipes, equipment, and coverings. It can clog irrigation systems and misters and is slippery which can cause safety hazards on walkways.
How to Clean a Greenhouse
- If the greenhouse has concrete floors, vacuum up any debris
- Use special greenhouse cleaners like Strip-It that are designed to remove algae and dirt or use soap and a high-pressure power washer to clean surfaces
- Clean the greenhouse from ceiling to floor by sweeping off walls and rafters then cleaning equipment and floors
- For dirt floors, install cloth weed barriers that resist algal growth and allow drainage
- Use a product such as Strip-It or SaniDate to clean irrigation systems of debris and eliminate any biofilm (microbe filled slime) that has built up.
Preventing Pest and Pathogens
- Fertilizer runoff and moisture will encourage algal growth; allow surfaces and growth medium to dry after cleaning and between watering
- Use tables and benches that can be disinfected; porous materials like wood can harbor algae and mold
- Pathogens like Pythium, Rhizoctonia, and Thielaviopsis can survive in the root debris of used soil; do not reuse containers and soil if growing pathogen prone crops or crops that have been contaminated
- If containers are to be reused, they should be cleaned and disinfected
Disinfectants for Greenhouse Cleaning
Quaternary ammonium (and Q-salt), hydrogen peroxide, peroxyacetic acid, octanoic acid, sodium carbonate peroxyhydrate, and chlorine bleach are all effective active ingredients to look for in a disinfectant for greenhouse use. Alcohol may be used for disinfecting propagation tools but is not generally used in greenhouse cleaning.
Always follow the instructions for preparation and use found on the product’s label. Disinfectants have a dwell time where a surface must remain wet with the product (or soak in the product) in order for it to effectively disinfect. For example, a 10% chlorine bleach solution needs to contact a surface for 10-20 minutes to sanitize it from most bacteria, but it needs 20-30 minutes of contact time to kill spores from fungi. Bleach can be a good cleaning product for day to day use, but a stronger disinfectant will be better for cleaning in between crop cycles.
Since bacteria can acclimate to particular cleaners, it is best to develop a rotation schedule where different active ingredients are used. Some active ingredients target certain bacteria better than others, so cleaning with multiple products ensures that a wider spectrum of pathogens is prevented. After cleaning with a sanitizer, it is a good idea to rinse with soap and water to remove any chemical residues that can build up and degrade materials.
Energy Efficiency Measures
Energy costs for greenhouses can be very costly. Approximately 75% of the energy used in a greenhouse is for heating, 15% for electricity, and 10% for vehicles. Focusing on the factors that use the most energy and ensuring that they are running efficiently and well maintained will help reduce energy costs overall.
Tips for Energy Efficiency
- Weatherstrip doors, vents, and fan openings
- Seal gaps around openings for stovepipes and chimneys
- Lubricate shutters frequently
- Use poly glazing with infrared inhibitors
- Insulate greenhouse perimeter below ground with 1-2” thick insulation board to reduce heat loss
- Insulate knee walls, sidewalls, and end walls up to bench height with insulation board, foam, or double bubble insulation
- Insulate around sidewall heat pipes and hot water pipes
- Install shade screens to aid cooling
- Check boiler, burner, and back up heat systems annually and have furnaces cleaned and adjusted
- Use a root-zone heat system (radiant in-ground heat) for better efficiency
- Use alternate fuels when possible (biomass burners, shell corn, cooking oil, solar power)
- Install controllers and thermostats (+/- 1°F accuracy) and check their accuracy annually
- For active ventilation, horizontal airflow systems will provide the most energy efficiency
The USDA Virtual Grower software can be used to calculate greenhouse heating costs and predict energy use for your greenhouse, it is also free!