What is Reseeding?
A plant, in order to reseed must meet a few requirements. It must:
Produce viable (fertile) mature seeds.
The seeds must be released from the plant.
The seeds must find safe ground to germinate in.
The seeds must survive over-wintering where they are: ie, not desiccate, not rot, not be eaten, and they must be tolerant of that particular region's coldest temperature in winter.
Survival of the fittest, as well as luck, are equal factors here, but it is often luck that is the determining factor for viable seeds to germinate in a natural setting.
If a plant can meet these needs it should be able to reproduce itself with new seedlings. These seedlings are entirely new and separate plants grown from seeds of the parent plant. This is not the same as a plant over-wintering with new growth coming from the original crown the following growing season.