Um, my garlic clove is turning green?

What you see: Green on the exterior of garlic What it is: Harmless chlorophyll Eat or toss: Eat!
Garlic may look kind of root-like, but it’s actually not a root — it’s modified leaves. The cloves? Those are storage leaves. The green sprout in the middle? That's a logically named sprout leaf. The papery coating of the entire head? That's made of dried foliage leaves.
You get the idea. Lots of leaf action here. So, while these bits of garlic anatomy may not look like leaves to us, they still act like them. This clove was probably exposed to a lot of sun, or a big influx of fertilizer. That would have caused it to produce chlorophyll and turn green, says Crystal Stewart, an extension vegetable specialist at Cornell. She notes out that in the image of the clove above, it's no surprise that the smooth, pointed area is sporting some green. That's the portion that used to be closest to the sun. And, of course, chlorophyll is entirely harmless. So, enjoy your roasted garlic or pesto or garlic bread or whatever tasty creation you have in mind.
SOURCES: Crystal Stewart - Extension Vegetable Specialist - Cornell Extension
The Complete Book of Garlic by Ted Jordan Meredith, p. 73 - 76