In my distant youth I thought I understood why (most) fruit trees were
grafted onto different root stock:-

The 'pure' fruit is difficult to grow from seed and isn't vigorous
enough to grow at a reasonable pace so bits of the original (Cox,
Bramley, whatever) are grafted onto a vigourously growing root
stock and off you go.


However I now believe this is somewhat simplistic and probably even
wrong. Among other things some rootstocks seem to be chosen to
inhibit the fruit tree so it doesn't grow too big as I understand it
now.

So, a couple of questions:-
Is it possible in general to grow fruit trees from seed or are
there other issues than vigour (or lack of vigour) that prevent
one doing this?

Does the same apply to all fruit trees (e.g. apples, pears,
cherries, plums, etc.) or is it only some types that are grafted
and others are 'complete' as it were.

What do the suckers on various fruit trees grow into if they are
left to grow? We get masses of suckers growing up from the roots
of our plum trees, often several yards away from the trees. Do
these grow into fruit bearing trees if separated and planted or do
they grow into the plum equivalent of a crab apple or some such?

We have an apple tree that I think grew from below the graft on a
tree that all but died. It's very vigorous! It's become quite a
sizeable tree in just a couple of years and bears a lot of fruit
already. Is it going to cause us any problems? (We have lots of
space - several acres altogether)

--
Chris Green