From the Super Mario Wiki
Nipper Spores are red spheres that are attached to white balls of fluff via small, green stems in Super Mario World 2: Yoshi's Island, Yoshi's Island: Super Mario Advance 3, Yoshi's Island DS and Yoshi's New Island. There are four Nipper Spores on one Nipper Dandelion. When strong gusts of wind blow (usually caused by Windbags), the Nipper Spores are blown off of the Nipper Dandelion and into the air, until they land and become Nipper Plants. No eggs are produced when Yoshi eats a Nipper Spore.
In Yoshi's Story, Nipper Spores have spikes on them. They are also foul tasting, meaning that they'll hurt any Yoshi (except for the Black and White Yoshi) that eats them.
Nipper Spores also appear in Mario & Luigi: Dream Team, where Piranha Plants in battle spit them out into the background to create Nipper Plants.
Nipper Spores reappear in Yoshi's Woolly World, acting the same as in previous games. Nipper Spore Patches, a related species, also appear.
- ^ Super Mario World 2: Yoshi's Island Nintendo Player's Guide. Page 128.