It fights like a combination of Choking Weed and Crystal Core. It's a giant mutated rose. It also has a blue bulb resembling a core.
This pretty flower is not a thing to mess with. Giga's Rose opens up, firing small bolts from it's tentacles and sucking you in. After this, it will close, and fire two streams of lasers while firing large seeds. These seeds then burst open to fire a three way shot at you. This pattern repeats until it dies, upon death, it withers, shrinks, and falls off the wall.