Due to how invasive some fungi are, some plants are impossible to unlock if you don't already know precisely the exact setup to unlock them. And boy are those setups convoluted to do.Greenrot:
Greenrot is bread from 1 White Mildew and 1 Ordinary Clover, at a weight of 0.005
That being said 1 White Mildew spreads on its own into Brown Mold at a weight of 0.5, which means you first need to prevent the grown of Brown Mold in order to get your Greenrot. In order to do that, you need to have 2 Brown Molds adjacent to every plot that could grow a Brown Mold. But since you're adding in Brown Mold to the mix, you also need to prevent its spread into White Mildew by having every plot where a White Mildew could spawn be adjacent to 2 White Mildew.
Then you have to consider that, by itself, the Ordinary Clover also spreads around if there are 2 or more clovers adjacent to 1 tile.
Conclusion: in order to successfully unlock Greenrot (mandatory to unlock 2 other plants), you need plots that are adjacent to 2 White Mildews, 2 Brown Molds, but no more than 1 Ordinary Clovers. Here's what this looks like:
(where red and dark red are the fungi and green is the clover, this gives you only 8 spots to grow stuff)
Suggestion to fix this: rebalancing the weight values so that Greenrot still has a chance to spawn even though other fungi could also potentially spawn there.Crumbspore:
Crumbspore is necessary to unlock 5 other plants, that being said it spreads on its own and its spread is only prevented if there are 3 other Crumbspores adjacent to where you want your plant to be. This means that in order to spawn any of the 5 new plants, you need plots that have 3 neighbouring Crumbspores and 1 other breeder plant. Once again, the setups are kinda ridiculous, and also frustrating if you consider that Crumbspore can destroy nearby plants (ie your breeder plants).
I go into much further details on this reddit post
, with pics and stuff.