[pbs soil temperatures, amaryllis belladonna flowering in NY, other stuff

penstemon penstemon@Q.com
Sat, 22 Aug 2015 09:27:24 PDT
>Very interesting data, which pretty much proves what most have suspected.  It would be interesting to see what soil temperatures are like at various depths in areas with much colder winters.  I wonder just how cold my Crinum bulbispermum bulbs experience when it is -1F outside as it was a couple of times this winter, and solidly frozen all February though with snow cover most of the time.  
Probably no where near as cold as you would imagine. Maybe just below freezing, as the Wiki article suggests. I think the minimum survivable temperature for almost any bulb is about 10F (-12C), which is why they (very sensibly, in my opinion) spend the winter underground. 
Denver has very cold winters, to –29C (-20F) at least, but Magnolia soulangeana is planted throughout the city, and its roots are only hardy to –3.9C (25F). 
So, the way I see it, if bulb experiences winter dormancy, and is planted in the ground instead of left out on the patio, it should be hardy. 
Bob Nold
Denver, Colorado, USA
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