Bitterbrush first-year seedling survival is low. To determine whether imbib
ition temperatures affected seedling vigor, I compared post-imbibition seed
weight, germination, and early growth among untreated, thiourea-treated, a
nd cool-moist-treated seeds from three collections. Seedling axial lengths
from untreated seeds averaged 28 mm among all imbibition temperatures. This
compared to 31 mm from thiourea-treated seeds, 68 mm from seed held at 5 d
egrees C for 14 days, and 118 mm from seeds held at 2 degrees C for 28 days
. There was no imbibition temperature for untreated or thiourea-treated see
ds that compensated for the lack of a cool-moist treatment. Seed treatments
or seedbed conditions which fully remove dormancy and reduce dormant-seed
respiration appear likely to increase seedling survival during the first gr
owing season. (C) 1999 Academic Press.