by Robin Nichols

Doug Mills Grows Orchids and More in his Greenhouse and Even a Terrarium

The Greenhouse

The 1,000 square foot greenhouse utilizes a 20’ x 50’ floor plan and is attached to the house. Heating is inexpensive, even in Iowa winters, due to a geothermal heating system and cooling is achieved with an evaporative pad cooling system. Ventilation includes two 2-speed fans and one variable speed fan for summer and one squirrel cage fan for winter. Shade cloth is used to help reduce summer heat.

Rain water caught in a barrel under an eave spout is the primary water source. Water caught in the rain barrel flows into two separate tanks, one with water only and one that includes fertilizer. A small pump is used for watering in the greenhouse with every other watering utilizing the fertilizer solution water. The system also includes a 200 gallon underground reserve tank as a safety precaution against summer drought. Snow is collected, melted and used for winter time watering. Most homeowner’s greenhouses aren’t this large and Doug estimates a 50 gallon tank collecting rain water would be more than adequate for their needs.

Long term projects include adding a system that floods the floor intermittently to keep humidity levels high and possibly a fogging system.

The Terrarium

Doug constructed his own terrarium using cedar wood purchased at a local retailer. It measures 4’ wide x 2’ deep by approximately 3’ high, contains a removable glass front and has holes drilled on the sides to help with ventilation. LED grow lights purchased are placed on the top of the terrarium and are scheduled to run 14 hours per day by using an automatic timer. The use of LEDs eliminates a lot of the heat build up associated with grow lights and as a result the day time temperature of the terrarium only reaches approximately 78 degrees or about 10 degrees warmer than the normal night time temperature of 68 degrees. Several regular lights have also been added that can be turned on for viewing purposes. The plants are misted each morning using rainwater that includes diluted nutrient solution.

Feeding the Plants

The plants in the greenhouse and terrarium receive diluted nutrient solutions in water. Doug has tried several different fertilizer and nutrient products successfully but primarily uses SuperThrive (http://www.superthrive.com/) and Orchid Focus (http://www.OrchidFocus.com/). He also uses Physan (http://www.physan.com/) as his primary disinfectant. Avoiding salt build up and using rainwater are the key factors he attributes to his success. Using rainwater, especially for orchids, is very important because the minerals in other water sources coat the roots and prevent absorption of the nutrients into the plants.

Tips from an Expert

Doug spends at least an hour a day in his greenhouse and offered a few suggestions for beginners:

• Consider purchasing or building a terrarium because they are the “great equalizer” and make growing very easy.
• Use rainwater if possible to avoid mineral build up and chlorine problems with plants. If rainwater isn’t available distilled water is a good alternative for terrariums as 5 gallons would last 3 months or longer.
• Don’t over fertilize your plants.
• Consider using LEDs because they keep the temperature down and require less cooling.

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Robin Nichols is the publisher of Garden & Greenhouse and may be contacted at 563.557.7571 or This e-mail address is being protected from spam bots, you need JavaScript enabled to view it .