The temperature of the propagation
medium should be high, and a general range for
floricultural crops would be 68 to 86°F. Most
seeds will germinate at 75°F, but one should
always check the germination requirements of
specific seed. Not only do specific species require
an optimum germination temperature, but some
seeds may or may not require light. There are a
number of excellent publications which contain
the germination requirements of herbaceous
plants (Nau, 1999; Styer and Koranski, 1997). If
seeds are to be covered, a general rule of thumb
is to cover the seed by a layer of loose propagation
substrate (coarse vermiculite or perlite is often
used) as thick as 1/4 the length of the seed. Along
with a light covering of mix or a mix component,
some growers will cover the flats with white or
black plastic to keep moisture levels high and
prevent rapid drying of the germination substrate.
The plastic is then removed after the