Many growers dispute the proper way to cure the garlic and cut the leaves and roots off for storage. Many growers wash their garlic and see nothing wrong with it while others are horrified by the thought. In my experience, garlic that is washed has a tendency to have wrinkled bulb wrappers that look a little like your fingers do right after a bath. It also seems to me that the extra moisture that accumulates in the bulb could lead to fungal infestation. Some cut the roots and leaves immediately, some wait a few weeks before trimming and some never trim their garlic. What is proper for one but not another may have to do with climate, humidity, human resources, cost of handling or available facilities.
We feel that garlic likes to dry down gradually in temperatures that are similar to those a few inches underground (about 72F). This initial drydown process is called curing the garlic. The idea is for the excess moisture in the roots and leaves to evaporate or withdraw into the bulb. When the roots and necks are completely dried and it does not emit a typical garlic odor when cut, that is the time to trim it. It usually takes two to four weeks to get to that point, longer for extra large bulbs. If you trim it while it is still moist and green, the fresh cuts expose the garlic to fungi, viruses and other contaminants that can set in and cause the garlic to spoil or pick up some disease you don't want it to have. With softneck garlics, many people braid them before they are completely dried down and are still pliable and never trim the roots while other braiders will trim the roots and flake off an outer bulb wrapper or two to make them more attractive.
After the garlic has cured, it is time to decide whether to trim or how much to trim it and how to store it so that it will last and still be good and healthy a few months later when it is time to plant next years crop or to last you for eating through the winter. USDA standards prescribe no more than a quarter-inch of root and no more than a half-inch of stem. I don't go along with that as I think it makes the garlic difficult to handle. We also use stem length as a means to identify certain garlics at a glance-different varieties of softnecks are cut to different lengths, that is, Locati will have longer stems than Rose du Var, to tell them apart at a glance since both look alike but taste different. It helps our customers identify them better, too. Many growers peel away the outer one or two layers of bulb wrappers in order to remove soil particles and contaminants and to make the bulbs more attractive to purchasers. If you have harvested your garlic at the right time, there should be several layers of bulb wrappers remaining.
Storing the Garlic.
As you might suspect, there is not widespread agreement among growers about storing the garlic any more than there is agreement about anything else. Again, you might try a few different things to see what works well for you. About the only thing that most people agree on is that it is bad to store garlic in plastic bags or sealed containers as these things promote rotting. They also agree that garlic should not be stored in direct sunlight.
Four factors affect the storage of garlic; namely, how well it was grown and cured, its varietal type, temperature and humidity. Garlic that was poorly grown and improperly cured will not get any better in storage. Some varieties naturally store longer than others. Silverskins are the longest storing , with Porcelains coming in second and Rocamboles being the shortest storing varieties, with Purple Stripes and Artichokes falling somewhere in the middle. Specific cultivars of each kind can vary from the pattern, but in general, this is the way it is.
Have you ever noticed that garlic that you buy at the supermarket doesn't seem to store very long once you take it home? There is a reason for that. The USDA recommends storing garlic at 32F, so most large chains of stores do that and require their suppliers to do likewise. Garlic stores well at that low temperature for a few months, (if the humidity isn't too high, which it sometimes is) but when you remove it from cold storage and place it on the shelf for sale, time catches up with it in a hurry. It either deteriorates rapidly or sprouts fairly soon and tries to grow. This makes for a garlic that is good for immediate use only.
We think garlic stores best long term when it is stored at between 55F and 65F and between 40% and 60% humidity. If the humidity stays below 40% for a couple of weeks or more, garlic has a tendency to dry out faster than it otherwise would. If humidity goes higher than 60% for any extended period of time, fungus and molds can set in. If the temperature goes below about 55F for an extended period of time, garlic tends to want to sprout and grow, even if it is not the right time of year (that's why the refrigerator is not a good place to store garlic). If temperatures stay much over 70F for any extended length of time, garlic tends to dry out and deteriorate. These are approximate ranges and need not be taken literally, but are very good guidelines. In our experience, garlic, except Rocamboles will store quite well for four to six months at between 65F and 75F as long as the humidity is moderate.
One of the advantages to keeping garlic around 55 F. is that fungi and other pathogens and pests are much less active than they are with the temp in the 75-80 F. range. Keeping them cool, but not cool enough to sprout them is the key to storing garlic well. It's pretty hard for the average person to achieve the proper temperature range for ideal storage of garlic.
It is important that airflow around the bulbs not be restricted too much as this hastens deterioration. A ventilated terra cotta storage jar is the best way to store garlic for the average person, since most people don't have grandpa's root cellar anymore. We have found that garlic stored in double paper bags in the shade in a normally air conditioned house seems to do pretty good. Of course, this isn't practical if you have several thousand bulbs, but works quite nicely for a few dozen. Basically, any dark, cool place is ok as long as the humidity is not excessive.
Good luck and enjoy the fruit of your labor. You will probably discover that you get much better tasting and longer storing garlic when you grow your own from selected cultivars than the garlic you get at the local supermarket. Enjoy.