Determining water need with a meat thermometer

[fredfarmer]

I know. I know. What the $%*@! Is this? Others are thinking maybe junior member posts should be reviewed before posting. But please hear me out.

I have a number of young Tolumnia that have been “potted” in 2 inch clay pots sitting in oversized clay saucers with a very small amount of tree fern to hold the roots in place inside the pots. It works rather well. They have to be watered frequently (every 24 to 60 hours dependent on ambient temperature and relative humidity) and a fan is directed on them to maintain enough air flow to make the larger leaves move slightly in the breeze.

I noticed that after about an hour of watering and lasting well into the next day that the clay pots were cool to the touch which I attribute to evaporative cooling. What I didn’t expect was the extent or uniformity of the cooling – until I decided to measure it with one of those rapid reading meat thermometers. I just stuck the needle tip into the media right next to the clay sides of the pots. I also weighed the pots as is my habit with newly acquired orchids to monitor water retention levels. Some results with 9 tolumnias are below. Note that the watering liquid was at ambient temperature (80 deg. F) for at least 24 hours prio to watering.

Hrs post watering: 2 hrs , 24 hrs , 48 hrs

Ave. wgt.– wgt. of: 35 g. , 21 g. . 14 g.
dry empty clay pot

Amb. temp minus: 4.7 deg , 5.9 deg , -0.1 deg

thermometer readiing

As the average initial weight of the Tolumnias themselves were in the range of 9 to 12 grams, it appears that at 48 hours they were pretty dry and the temperature reading on the me at thermometer was basically the same as ambient temperature. As I can determine the thermometer reading without moving the Tolumnia filled pots, it’s a convenient way to determine when to water any given pot without getting out the scale and moving it back and forth into position under the LED lights.

Not sure this will work for everyone, but maybe some inside-under-lights growers will find it useful.

My next effort will be to figure out how to make a table inside an OB post.