From the Super Mario Wiki
Egg-Plants are flowers that are found in Super Mario World 2: Yoshi's Island, Yoshi's Island: Super Mario Advance 3, Yoshi's Island DS, Yoshi's New Island and Yoshi's Woolly World. These flowers normally spit out normal Yoshi Eggs. They are very common and appear in almost every level. They spit out Yoshi Eggs one at a time, but if a Yoshi Ground Pounds near one, the plant will either shoot out several at once or start shooting them out more quickly. The Yoshi can also lick the eggs to catch them. Since the Yoshi can only carry six eggs each, the Egg-Plant won't produce more eggs anymore until the Yoshi uses one of the Yoshi Eggs on something.
The Egg-Plant's name comes from the eggplant, a type of fruit. It also shares its name with a type of nightshade (hence the appearance).
Also, some Egg-Plants will spit out Needlenoses, but as long as a Yoshi has six eggs, it can't spit any out. There are four Needlenose-spitting Egg-Plants in the Island Museum. They can be viewed in the botanical enemy exhibit.
An Egg-Plant providing an egg for Mario.
An Egg-Plant appears in the Super Mario-Kun volume 14, where it helps Mario, Yoshi, and Luigi by providing eggs in their fight against Burt the Bashful.
In Yoshi's Woolly World Egg Plants are knitted and in replacement for eggs, they shoot out yarn balls of multiple colors. Egg Plants appear less frequently in the game, with only a few appearances. Notably, Egg Plants don't have a variation that spit out Needlenoses in this game.
- ^ Super Mario World 2: Yoshi's Island Nintendo Player's Guide. Page 128.