cold definitions

Fall
- Sep 15-Nov 1-- drop temperature from 65 ° to 35 °, over 4-6 weeks, 5 °/wk

Winter
- vernalize: cold 35-45°F for 6-12wks needed for many perennials to flower
- colder and roots may go dormant
- if foliage, ambient light or 25-50ft-c

Fall