(last upadated March 5th, 2008)

Garlic is my very favorite crop in my home garden. Aside from my love of the Stinking Rose itself, garlic provides me with a project to keep me out of trouble long after most of my vegetable garden has succumbed to frost.
My New Hampshire garden is in Zone 5a, with winter lows bottoming out around -15°F to -20°F on average. This makes it well-suited to hard-neck varieties which actually like the cold weather.
I am told by a friend that this guide almost intimidated her into not planting the garlic I sent. It was too detailed; her husband commented that it looked too complicated for Sunday gardeners like them.
Don't worry: growing garlic is easy! You don't need to follow all these suggestions, or most of them, or even any of them. Push a couple of cloves down into the ground, and chances are your garlic will grow.
That is how I started: I purchased a few bulbs of an unidentified garlic grown by my local organic farm stand*, split the bulbs into cloves, and pushed them into the soil, and pretty much ignored them until the scapes appeared in July (what were those funky looking things?). The easy success of that crop led me to purchase seed garlic on the web and eventually to my current obsession. I now grow over two-dozen varieties, including that local version (which I have dubbed Roc Jerome as it appears to be a Rocambole, and is ready to harvest on Jerry Garcia's birthday.
*One warning: most garlic purchased in your local grocery store has been treated so it will not sprout, and will not grow. Try a local farm stand that grows their own (it will be suitable for your climate), or order some seed stock online (there are some suggested sources below), or get some free garlic with your Dharma Rose order in the Fall.
Autumn
Typically, hardneck garlic should be planted about six to eight weeks before the ground starts to freeze. For me, that means mid to late October, though I often continue into the first week of November
In the Fall of 2007 I planted 28 varieties. I grow my garlic in 4' wide beds, rotating my crops so that each bed gets at least two years off before they grow garlic again.
While garlic is forgiving, it does like fertile soil, so I add 2" of composted manure and mix it well into the soil. This bed is a young raised bed, as compost gets added each year the soil will eventually rise to 8" above ground level.
The planting ritual starts with sorting and selecting your planting stock. I choose only the largest cloves from the largest bulbs as smaller cloves will merely yield small and unsatisfactory bulbs. I save the other cloves for my kitchen, and for growing green garlic (more on this later).
The night before I intend to plant, I break the bulbs carefully into individual cloves. (These cloves should be planted within 2-3 days.) I first run my thumbnail around the stalk just above the cloves to break the wrapper there and again, very carefully, break the wrappers between cloves on opposite sides of the bulb. I then can easily break the bulb in half and separate it into individual cloves.
I generally know how many cloves I want to plant of each variety so I sort the cloves into three categories: ideal, satisfactory, and unsatisfactory. Some varieties of garlic are prone to "double-cloves" which will yield two bulbs joined together (usually there will be a marked depression running the length of such cloves). I prefer not to plant such cloves and add them to the unsatisfactory category. After counting the number of ideal cloves I have, I make up any difference from the satisfactory cloves (largest first), and revise my target downwards if necessary.
I plant most of my varieties in a 6" grid; I grow a few of my smaller-bulbed (1.5" or less) types in a 4" grid. Commercial growers usually recommend growing in double rows to allow more sunlight, but given my setup that is impractical and I am satisfied with the grid layout in my 4' wide beds. I leave a full 12" between different varieties.
When I plant, I set small bamboo stakes at 6" intervals and use a half-inch PVC pipe which I have marked off at 6" and 4" to layout my rows of garlic. I use a fat bamboo stake to create each individual hole, "stirring" it into the soil to make a hole about 1.5" wide and 3" deep. The target is to have the tip of the clove about 2" below the surface of the soil.
After "digging" each hole in the half-row (I work the two sides of the bed separately; the stakes help me keep the rows contiguous) I set a clove into each hole the flatter root end (basal plate) down and the pointed growing tip up, gently pressing the clove in so it has good contact with the soil below. When I am done setting out all my cloves I smooth out and gently pat the soil, filling in the holes.
The last step is adding a layer of mulch. I use about 4" - 6" of straw or hay, but you can also use chopped leaves or grass clippings. The latter two can matt down, and should be removed in the Spring, or they may prevent some of your garlic from sprouting.

Spring
Some farmers remove the mulch from their garlic in the Spring regardless of the type used. I have found that most of mine have no trouble punching through the hay that I lay down, but I may lose up to half of several varieties (turbans in particular) if I do not remove the mulch. In those instances, I try to replace the mulch around the plants once they are established to control weeds and moisture. Some do not bother to re-mulch, but weeds need to be kept in check as garlic (like all crops) do not appreciate competition.

Summer - Scapes
Early in July, hardneck garlic varieties send up flower stalks called scapes. As they grow they will curl, often 360° - 540°, and eventually make bulbils which can also be used to grow garlic. Most farmers cut off the scapes when they start to curl to encourage large bulb size. I cut (most of) mine when they have a 180° bend, and do so to harvest the scapes more than in the hopes of larger bulbs (evidence indicates that larger bulbs are probable).
The scapes are delicious and versatile. I find that they keep refrigerated for over a month. I chop them up and use them on salads, in salsa, pesto, omelettes, pasta sauces, and and anything else I can think of. If you plan to eat your scapes, it is important to harvest them early as they get hard (wooden) as they mature. I enjoy the scapes as much as I do the bulbs themselves.
I do leave some scapes to develop for varieties with large bulbils (pea-sized or larger — Rocamboles, in particular). As mentioned above, bulbils can be used to grow garlic. The downside is that they take 2-3 years to create full-sized bulbs. However, large bulbils can create "rounds" in the first year, undifferentiated bulbs which look more like round onions as they do not have individual cloves. I have found that some rounds grow into extra-large bulbs the following year; in some cases larger than those produced from even my largest cloves. I am still experimenting on which varieties do best from bulbils, planting them about 2" apart and 1" deep. For varieties with small or tiny bulbils (Porcelains, for example), I find no advantage to leaving any scapes.

Harvest
While a few of my varieties are ready to harvest in early July, my busy period is the last two weeks through the first week of August. The rule of thumb is to harvest when half the leaves on half the plants have started to brown. If you harvest too early you sacrifice some size, but if you harvest too late there will be few, if any, wrappers left intact and the bulbs will not store well.
I grasp the stalk just above the ground and the bulbs usually come up easily. Gently dig if you encounter too much resistance. I bundle them in bunches of 12-15, and hang them to dry in our barn for 3-4 weeks. Any shaded location sheltered from rain will do.
While many may find cleaning tedious, it is one of my favorite events in the cycle. You take an ugly bulb encrusted in dirt and uncover the gem within. I trim the stalk first, leaving about 2" for aesthetic reasons (and aesthetics are paramount), then rub off the loose soil with my hand. Using a toothbrush I next clean the roots, and use the bristles to carefully peel of a layer or two of wrapper, just enough to leave the bulb shining. The last step is to trim the roots with a pair of scissors; I leave about an inch.

Garlic Seed Stock Suppliers
I have purchased garlic seed stock from each of these farms, and was entirely satisfied with the result. They were all friendly and helpful, though I feel that Filaree and Garlicsmiths both went well beyond the call of duty.
Filaree Farms - "Located in north central Washington State where we've been farming organically since 1977. Filaree offers over 100 unique strains of seed garlic which we have collected from sources all over the world."
The Garlicsmiths - "Garlicsmiths is a small family farm business located in northeastern Washington, certified organic by the Washington State Department of Agriculture and the USDA."
The Garlic Store - This distributor was one of my first suppliers. "TheGarlicStore.com is a Certified Organic Processor/Handler by the Colorado Department of Agriculture. We only sell garlic that is grown in the U.S.A."
Gourmet Garlic Gardens - A large seed garlic store based in Texas. They grow some of the garlic they sell, but also purchase stock from other growers.
Snakeroot Farms - This kind organic farm in Maine only offers one variety of garlic (Red German), but they also sell large bulbils should you want to try planting those. This is a nice site with lots of helpful information.