Is it too late to plant garlic now for fall harvest? And can I grow it from the garlic cloves I buy in the store?

Sorry, but I'm afraid so. You are in the NE US? You would probably have had to plant garlic around October or November, and mulched heavily after the first hard frost and would be just thinking about harvesting either in late July to August. Gardenz is possibly in your area, and she'd be able to say for certain. This is how it is for me here in zone 4 MN.

And yes you can. Break it apart into cloves and plant individually, pointy end up.

You need to plant in October...when you plant daffodils or tulips.

You can plant storebought cloves, but you have time to get seed garlic from some interesting varieties.

I grew garlic from store-bought bulbs last year and had good results. It was organic, and the cloves had already started sprouting which was a good sign to me that it would grow. You may or may not have as good a result from conventionally-grown.

Now is the time to choose what you wanna plant for next years harvest. Look at your organic grocery, or farmers market. Some of the garlic in our city garden has been growing for over ten years. I like to find different varieties and see how they grow.