Seeds are made when pollen from one plant
lands on an egg in another plant.
In some plants, the eggs are in flowers. The
plant makes a sweet water called nectar to get
bees, hummingbirds, bats, or other animals to
visit. The animals visit several flowers, so they
bring the pollen from one plant to the eggs of the
Other plants have no flowers. The wind blows
the pollen onto cones or other places.
Why do you think seeds would not be formed
underground in roots?
If you are interested in questions like these,
you may want to study botany or ecology.
Thanks for asking