TABLE 1

Differences in photoperiod at time of germination and bolting among the seasonal environments and geographic regions

EnvironmentApproximate
date of
germination
Date of first
bolting
Days to
first
bolting
Average
days to
bolting
Shortest photoperiod
between germination
and bolting
Photoperiod
at bolting
Fall
    Rhode IslandOct. 17-19March 11341509 hr 09 min11 hr 14 min
    North CarolinaOct. 31-Nov. 3December 19497310 hr 26 min9 hr 45 min
Spring
    Rhode IslandMarch 21-23April 28384412 hr 10 min13 hr 53 min
    North CarolinaFeb. 22-24April 15526011 hr 09 min13 hr 05 min
  • Dates of germination are the dates on which the seed stratification treatments ended and seed trays were placed under ambient photoperiods. Date of first bolting indicates the date the first plants in a cohort began bolting, that is, differentiated a flowering inflorescence, while days to bolting is the absolute number of days elapsed between the time of germination to the time of bolting. The following column provides the average number of days to bolting for a cohort. Because changes in day length may influence bolting date, the shortest photoperiod experienced by a cohort after planting, in addition to the photoperiod on the date of bolting, are presented in the last two columns. Note that the North Carolina fall and Rhode Island spring cohorts experienced day lengths consistently shorter and longer than 12 hr, respectively, from the time of germination to bolting, while the other two cohorts experienced increasing day lengths prior to bolting.