Mushroom allows Kinoko to instantly grow mushrooms anywhere.
Kinoko's body naturally releases spores that are capable of traveling very far depending on the location's humidity. Once those spores make contact with any surface, mushrooms will start growing in those spots at an alarming pace. She demonstrates the ability to manually choose where her mushrooms can grow so long as the spores are able to reach that area.
Kinoko has access to at least two spray bottles that she uses to increase an area's humidity levels, allowing her spores to scatter more easily. She is able to completely cover a terrain with mushrooms in a few minutes through this method, however, in order to prevent her teammates from being affected, they must be sterilized with an antifungal spray first. As a last resort, Kinoko is also capable of growing a mushroom within her opponent's throat, in order to put them in a state of asphyxiation. 
Kinoko's ability works well with Black and Comic, as the former can take advantage of black mushrooms to use as a hiding spot while the latter is able to amplify humidity through the right onomatopoeia, increasing the rate of mushroom growth.
The mushrooms that she has shown to be capable of growing include:
- Ionomidotis Irregularis
- Tricholoma Equestre
- Flammulina Velutipes
- Coprinopsis Atramentaria
- Schizophyllum Commune 
- Mushroom - Wikipedia article about the lifeform Kinoko is capable of growing.
- Spore - Wikipedia article about the reproductive cell Kinoko can produce.
- Fungicide - Wikipedia article about substances that are highly effective against Kinoko's Quirk.