how do people manage to get enough bushes/trees?

[Reese]

Can't you buy unlimited bushes from the island and replace them later?

It takes quite a bit of time & effort to earn medals, I personally wouldn't want to spend a bunch of them on bushes I know I'm just gonna dig up later. Buying them to trade them might be viable, as I and others have suggested (not specifically about the island bushes but trading in general)

 

[LuciaMew]

You can trade the bush that you don't need for the one that you need