I got this from Texas A&M's PlantAnswers site:

"What about another stinkerÂgarlic? A first word of warning--DON'T plant garlic in the spring! Bulb formation in garlic occurs in response to the lengthening days of spring, and bulbing and maturity are considerably hastened if temperatures are high. In addition to these requirements, the dormant cloves (divisions of the large bulb) or young growing plants must be exposed to cold temperatures between 32 and 50 degrees F. for 1 or 2 months in order to initiate bulbing. Plants that are never exposed to temperatures below 65 degrees F. may fail to form bulbs. With fall plantings, the cold treatment is accomplished quite naturally throughout the winter, but a spring planting spells disaster.

Seedstalk formation (bolting) of garlic is not induced by exposure to fluctuating temperatures, as is the case with onions. This means that a wide range of fall planting dates is permissible for this crop. Seedstalk formation is also not damaging to garlic since the cloves are arranged around the seedstalk and will be removed from the dried seedstalk. Conversely, the edible onion bulb is penetrated by the seedstalk that is hard when the bulb is harvested, but prematurely decays causing loss of the entire bulb in storage.

When the tops become yellowish and partly dry, garlic is ready for harvest. The bulbs are usually pulled and gathered into windrows. The tops are placed uppermost in the windrow to protect the bulbs from the sun, and the garlic is left in the garden for a week or more to dry (cure) thoroughly. Curing can also be accomplished in a well-ventilated shed. The cloves must be thoroughly dried before being stored. When properly cured, garlic stores well under a wide range of temperatures."

It needs cold temps so I'd still wait til fall. We usually plant in October.

Hope this helps.

Mark

I planted some in the spring, March. They grew but only to about the size of green onions.

Mark, thanks for your information. I'll try to control my impatience and wait until October!