I've left entire bulbs of garlic in the ground to use as garlic scallions. All the cloves will sprout up to grow in a nice little clump and will be ready for harvest in mid spring. And in all honesty, I feel like you get more garlic overall that way than if you were to just harvest mature bulbs. Not only can you use all of the garlic scallion, from the roots to the tips of the leaves, but they also dehydrate and preserve beautifully. Bulbs still have the advantage of being able to be used fresh in recipes throughout the year, but for stuff like homemade garlic powder, herb salt, for seasoning mixes or even as pickled garlic, I feel like garlic scallions are the way to go.

I've got walking onions that I use for green onions or scallions. The maturing plants will flower and produce topsets during summer, but if you keep some topsets on hand from the previous year (they store well) you can plant them throughout the growing season and have fresh scallions pretty much all the time.

Rodney