Greenhouse watering controls

One of the orchid benches

The greenhouse is set up to take care of itself. It has water, electricity and natural gas. There is a heater, an exhaust fan, four air circulation fans, and both watering and misting.

The minumum temperature in winter is 60 degrees, the minimum humidity 45% and maximum temperature 90 degrees. Exposure is north, west and south. Light level tops out at 4000 foot candles with areas shaded down to 2000. It is a manageable size, 8' wide x 12' long x 9' high. The walls are recycled windows and are vertical. The roof is a double layer of fiberglass with an air space between. There are dowels for hanging plants over the whole roof area.

I have the best of both worlds! I can travel and know that everything will still be alive when I get back. I visit the orchids daily and watch each development with interest. At the same time care is minimal. I enjoy the plants and putter without the maintenance becoming tedious.




Timer for rain Timer for misting Thermostat for constant misting Thermostat for raising humidity Humidistat for raising humidity 110 volt power
This timer is for controling the rain. There are two sets of overhead sprayers, one set for the south side, another set for the north side. They run early in the day with the north side running longer than the south side. The watering is about the same as a heavy rain. Since everything is either mounted or potted in gravel, heavy watering is ok.
This timer controls the overhead misting. However, the valve is not on until both a therostat and a humidistat also turn it on. Right now the misting criteria are:
  • Time from 11:00 am until 2:30 pm. Plants need time to dry out.
  • Temperature above 80 degrees. Cold and wet causes rot.
  • Humidity below 50%. Orchids can tollerate heat if the humidity stays up.
This thermostat controls misting. It is set at 90 degrees and turns the overhead misters on continuously until the temperature drops back to below 90. Orchids can tollerate heat if the humidity stays up. Even if this is late in the day, at this temperature there will be time for the plants to dry.
This thermostat is in series with a timer and a humidistat. It is set at 80 degrees which is the minimum temperature for misting. The overhead misters don't run in a cold greenhouse.
The humidistat is set to turn on the overhead misters when the humidity is below 50%. It operates in series with a timer and a thermostat so that misting will not take place when it is too cold or it is too late in the day.
Power is available in three corners of the greenhouse and runs the timers, the air circulation fans (which run 24/7) and the exhaust fan.