soil temperature variation with depth in a bulb garden

M. Gastil-Buhl
Fri, 22 Nov 2013 08:21:30 PST
Dave wrote
"For instance, a cold, hard rain after a dry spell chills deeper."
Serendipitously, the first big storm of the growing season fell  
yesterday with 0.89 inches (2.3 cm) inches of rain. The ground was  
already slightly damp from stored rain water I had used to irrigate a  
few days prior. I explored with a trowel in a nearby bed to the trial  
just now and can see the soil is only just damp, not soggy, but it is  
evenly damp (as judged from color) at least 6 inches (15 cm) down. So  
although it was not the original plan, we will see the temperature  
change from that rain storm.

Dave asks:
"where did you find these thermistor devices?"
The iButton was recommended to me by some ecology researchers. These  
are manufactured by Maxim but they are re-sold by many vendors. I use  
this one:…
I notice just today they went up in price significantly. To connect  
them to a computer I use the little blue USB plug and the "Receptor  
Interface Cable" the buttons snap into. Those are shown here:…
These iButtons are not waterproof, only water resistant. I sure hope  
mine are ok after that rain storm. We'll know on Saturday.

Peter has been doing my homework for me, reading that thick textbook.  
He writes:
"Temperatures less than 17 C apparently act as chilling for certain  
'dutch' Iris for example."
That is particularly relevant to this experiment because dutch iris  
are one of the bulbs which thrive in my garden without any special  
care. They multiply rapidly and bloom reliably. They do like to be  
planted fairly deep here, around 5 to 6 inches from soil surface to  
bulb base. No fertilizer, no irrigation, no shading, no care, and they  
bloom like a magazine cover. So that is a good reference point for  
soil climate.

I like Peter's idea of shading prior to emergence but I would shift  
that to Sept-Nov, the time when the bulbs may begin to be wet but the  
weather has not yet turned cold. (November can get cool.)

- Gastil

P.S. (off topic)
Dave refers to a photo on Flickr where I am shown holding a ruler up  
to a bloom stalk of Aristea capitata, which seems to like my climate.

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