I'd use the leaves now and then as garlic greens, kind of like scallions. Pull it in September and use the whole plant.

You can try to pull now and replant in the fall at the proper time for your area. For me it's September for the largest cloves to be harvested in June. Garlic needs all winter to grow long healthy roots which will contribute to bulb growth in the spring to be harvested in early summer. If you want garlic, plant it at the proper time for your area.

Check with your state's Extension Service. Each county should have it's own Cooperative Extension Office which provides free publications and information for the asking. They will have valuable vegetable/gardening tables available specifically for your area determined by universities and horticultural research scientists who have collected data from growing those crops in your state. Your tax dollars are already paying for this service so you may as well get some use out of it.

Vegetable Planting and Planning Calendar for Missouri (download the pdf) complete with spring and fall planting dates (underneath the spring planting dates for appropriate crops), how much to plant per person, etc. They can also tell you the average last frost date for your area and ideal planting times for specific crops and varieties in your area.

See how detailed this example is:

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