I think that all trees in Valheim should drop A LOT of seeds. But to keep fine wood rare birches and oaks should take much longer to grow instead. This would be more realitic as the average tree (if it is the right season for seeds) has hundreds to thousands of seeds. Also, trees with harder wood generally take longer to mature.
Then, if seeds could be in as large of stacks as gold, and be used to craft leaf piles (as a sort of stand in for all the greenery that falls off trees) people could create an autumn effect. I think they should be suject to decay however, so leaf piles would go away unless indoors. This way extra seeds would get used up and not just become another item that needs to be thrown away.