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: http://embeddeddatasystems.com/DS1921G-F5--Thermoc… 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: http://embeddeddatasystems.com/SK-IB-R--iButton-Co… 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.