http://www.raintreenursery.com/chill_hours.cfm
http://www.raintreenursery.com/indexpics/chill-unit-map3.gif
Does not include Canada.
<Chill hours are roughly the number of hours between the temperatures of
32-45 degrees fahrenheit. Winter hours above 60 degrees are subtracted
from the totals.>
These numbers are air temperatures for fruit trees. I'm not sure how
this relates to seeds in dirt. Might be more if in shade & under
reflective mulch, less if exposed. Map is a little hard to read, but I
think 3400 hrs (~= 4.7 months of continuous chill in a fridge) is the
most shown on this map. In northwestern Washington, extending into the
farthest northwest corner of Oregon. Looks like Salem might be around
2800 hrs or (ta da) 3.8 months.
If vernalization of seeds can occur at warmer temperatures (i.e., 55oF),
seems like the number of chill days could double. But I've not been
able to find data for that.
Linda Mann
TN
outdoor chilling = ~1300 hrs, according to map.
