Burgeoning Spiderwort mold
The Burgeoning Spiderwort mold is a bulbous structure lurking where berry-bearing Burgeoning Spiderwort plants had once grown. This fungus appears occasionally, but it is destructible, so if spotted, one should take a medium-large group of Pikmin to the area and have them attack it. Soon enough, the mold and its thread-like hyphae will slowly disappear, allowing the Burgeoning Spiderwort and any Pellet Posies that were there to grow once again. This is not harmful to the Pikmin, only to the plant.
In the Awakening Wood, there is a large piece of mold near the landing site, where two Spiderworts grow. It seals away both of the plants, but when eliminated, they will grow back.
In the Perplexing Pool, there are two of them across from the landing site (near the location of the Gherkin Gate). There is a Swooping Snitchbug there as well as a Fiery Blowhog, so it is advised to defeat them first.
In the Wistful Wild, there are three patches of mold in a large clearing near the drainable lake which coincides with The Final Trial's landing area in Pikmin. Each one covers its own berry plant, so it may take a while to get rid of them all.