Annuals, Biennials and Perennials
At the end of their cycle, do they reseed?
Certified GKH Gardening Expert
These question has many variables.
If a plant produces seed and it is provided the needed environment to seed; and the seed is viable.
Many plants are hybrids and the off spring may not resemble the parent plant.
It is best to research each plant individually to learn if it reseeds itself.
Gardening Know How is a great source for this type of research. Use the search bar at the top of the page.