For those of you who like challenging treasure hunts, the developers have practically made a mini-game of looking for Special Seeds in Twinbrook without a Collection Helper. The seeds are most abundant at the (I guess you'd call them) mudflats in the marshy area near the bridges, opposite the main town. Those big white seeds definitely don't stand out like they do on bright green grass. In fact, they congregate under trees, amongst tall, non-vanishing reeds and grasses, and to top it all off, there's usually ground fog obscuring the view. Finally found a seed? Nope, it's usually Unknown Rares or Uncommons, not the Special ones that yield Money Trees, Deathflowers, Life Fruits, or Flame Fruits. The Special ones are there, but they're few and may not spawn until another day.
I've also noticed that the 5 or 6 seeds that spawn outside the graveyard are most usually not Special Seeds, and need to be checked frequently to find one.