Sunday, November 23, 2008

Meters in the greenhouse

There are three things that are important to know about an orchid-growing environment: temperature, light level and humidity. These cannot be judged well without the use of meters.

Since my greenhouse is close to my home, I can use an inexpensive remote thermometer. It has a reliable range of 50 feet. It can read from three remote sensors, but I only use one. The primary information I need from it is whether the heater is on and how hot the greenhouse is getting in the daytime.

The primary reason that orchids don't bloom is not enough light. The human eye is especially bad at judging light. While being able to adapt to a range of light levels is good in most cases, it doesn't serve well in the greenhouse.

There are two models of inexpensive light meters: one with a separate sensor and one with the sensors in the top. I have had both and prefer the meter with the built-in sensors. It can be operated with one hand and is much less directional, both better traits for working in the greenhouse. The total amount of light on the leaf is more important than light from the brightest direction.

Greenhouses have microclimates. Even with three fans moving the air there is a wide variation. To monitor them and help with plant placement I have three of inexpensive thermometer-hygrometer sets in different parts of the greenhouse. These are not very accurate but they are consistent.

I took them apart and placed them side-by side for an hour, then I set them so they read the same as the remote sensor and the same as each other for humidity. They have lasted very well and can be in locations where they get wet.

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