If a seed germinates within a certain range of temperatures, and the soil isn't within that temperature range, some people won't sow the seed at that time. Especially because there is a danger of seeds rotting in cold, wet soil. If you're a farmer planting several acres, you can imagine what kind of loss that would be.
I did a little research and found that you're supposed to insert it 2"-3" if you're sowing seeds or deeper if you're transplanting.
