Seed Starting PhD: Germination as affected by temperature

In the seed starting class, I remarked briefly on the effective of temperature on how many of your seeds germination. Here's the data for that relationship.

http://tomclothier.hort.net/page11.html

I don't know the HTML yet for inserting a table, so you'll have to look at the page for the table.

One example is onion seeds:

If you direct sow your onion seeds now and assume your soil is frozen or about 32 degrees, you will get 90% germination. But at 32 degrees, it takes 136 days for an onion seed to germinate. Fortunately, the soil won't stay 32 degrees for 136 degrees, but basically the seeds are going to sit there until soil temperatures get ALOT warmer.

If you germinate them inside or somewhere you can keep the temperature at 68 degrees, 99% of them will germinate in 5 days. This is why we germinate onions indoors and plant them out later.