I can't be very specific at the moment because I can't load up my game, but I recall finding special seed in a couple of places.
Go into map view and have the water at the bottom of the screen. There is a building in the bottom left hand corner (can't remember, but it could be the junkyard) Look around that lot - behind and at the sides. Also there is a road that leaves town and follows the coast (sort of) to the right. Just out of town the road is heading towards the coast, then it curves to follow the line of the coast more. Where it curves, on the water side, there is a grassy area. I've found special seed there too.
Of course, you could always use the collection helper to find the location of seeds.
Hope these locations help.
I'm going to move this thread as it is not so much a skill related question (I know gardening is a skill), but rather a Showtime question as it relates to Starlight Shores.