White Kryptonite

'White Kryptonite

This scarce form of Kryptonite, which is harmless to Superman and all other Kryptonian survivors but emits a radiation that “destroys all plant life,” was brought into being when a flock of Green Kryptonite meteors passed through a weird “space cloud” somewhere in the vast reaches of interstellar pace. Supergirl uses a chunk of White Kryptonite to destroy the diabolical extraterrestrial “plant intelligence” Xasnu in July 1961 (Act No. 278: “The Super Powers of Perry White!”).