Five Fact Friday: Seed Dormancy

1. Some seeds will only germinate after they have had a period of drying, while others need a really good soaking.
2. Some seeds will germinate when fresh, which is common in the tropics. Others cannot do so because they have a thick seed cover that is impermeable to oxygen and water - these seeds need their coats wearing down and weakening over time.
3. Some seeds will only germinate after a cold snap where the conditions are around 5 degrees centigrade. Others require a warm snap to get them on their way. This is known as thermodormancy.
4. Known as photodormancy, some seeds require light in order to germinate, while in other seeds light will actually inhibit germination
5. Some really difficult to germinate seeds require multiple dormancies, whereby they need the right conditions to present themselves twice. For instance the first dormancy may break open an impermeable seed coat, but the seed it still dormant until a cold snap awakens it.

References:
RHS The Garden, February 2013. Lancaster, N
http://en.wikipedia.org/wiki/Seed#Seed_dormancy