Re: How does temperature effect germination?

A higher temperature will speed germination but eventually, above a certain 
limit, it then slows or prevents germination. There is also a minimum 
temperature below which germination will not occur. So each species has a 
minimum, optimum, and maximum temperature for germination. The optimal range is 
77 to 86 degress F for most species. Alternating day and night temperatures 
give better germination than constant tempertures. An 18 degree F difference 
between day and night is optimal.

Some seeds require stratification before they will germinate. Stratification is 
a period of several weeks to several months of cold (around 40 degrees F), 
moist storage. 

Reference

Hartmann, H.T. and Kester, D.E. 1983. Plant Propagation: Principles and 
Perspectives. Englewood Cliffs, NJ: Prentice-Hall.