i got my horn (suezo/tiger) to grade A 4th rank and the shop keeper didnt give me any seeds what do i need to do to get them?

I am not sure. Try to go to the item shop the whole month of February. If that does not work, try the item shop every week of a year. Do not, I repeat, DO NOT go above R4. It is impossible to get the seeds after that.

You have to visit the item shop a lot, during non-sale weeks.

on my last game i got them straight away

It's one of those random events that make the game harder in some ways, but also make it a lot more playable in the long run. If everything happened with set timing, then we'd all get less replay value out of it.

I've also seen it mentioned that you may only be able to get the seeds if you get to that rank in the first however many years of the game. I couldn't manage to get them in a game where I first reached that rank fairly later in the game, but in other games I've started where I've reached fourth rank fairly quickly, I've gotten the seeds fairly easily as well.

it seems as though the people who have had trouble with the seeds have either not gotten to rank 4 before 1020, or who blew right past rank 4 and got into higher ranks without visiting the shop much while they were there.

i say 'seems' because i am relying on memory of a few years of posts, and i am probably oversimplifying.

I'm not sure, but I remember reading in one of my Japanese MR books that you have to reach rank 4 before year 1010. I'll look it up when I get home tonight and report tomorrow.

on my old game i reached rank 4 in the year 1029 and got the seeds straight away