Trim the ends of 1 bunch of asparagus. Cut the spears in half lengthwise.
Fill a large pan with water just deep enough to cover the spears lying down. Bring a boil then blanch them (in batches if necessary), adding them to the water and then removing when it comes to a boil. Immediately dunk in very or ice cold water. Drain.
Boil a pot of water large enough to fit two pint jars completely.
In another pan, combine 1 C. white vinegar with 1 C. water. Add 1 roughly chopped green garlic, stem and bulb, plus 1 T. salt and a pinch each of hot pepper flakes, allspice, cumin seed, and coriander seed. Bring to a boil and stir a few times, then remove from heat.
Boil 2 wide-mouth pint canning jars with their lids and rings. Remove with a tongs.
Pack the asparagus into the two jars tightly. Pour the liquid over them, leaving a half inch of air space. Wipe any liquid off the rims of the jars with a clean towel, then place the lids on top and tighten with the rings — but not super tight.
Place a rack on the bottom of the pot of water and then stand the jars upright on it. The jars should be completely covered with water. Bring to a boil and cook on a gentle boil for 10 minutes. Shut the heat off and leave the jars in the pot for another five minutes before removing.
Allow the jars to rest for at least six hours. After a day check the seals; the button on top of the lid should be tightly sucked down.
Store asparagus for at least 4 weeks in a dark, cool spot before using.