In article ,
Michael Bell wrote:

I am trying to develop alder as a grain crop. One of the things I want
is bigger seeds.

Yes. As people have commented before, good luck, because you will
need it!

So, how do tree seeds normally spread? In the case of hazel, oak, etc,
obviously birds and squirrels, and they are the right size to be
attractive to these creatures. Alder seeds seem too small.

Birch is related, and they are distributed by the wind for quite
a long way, and can be a real pain. Naturally, that selects against
becoming large. I don't know about alder.