Prepare for water bath canning. Add 4 1-quart canning jars with lids to a large canning or stock pot. Fill the pot with enough water to cover the jars with one inch of water. Bring to a boil over high heat. Covering the pot with the lid will speed up the process.
Fill a medium size stock pot or large pot about half full with water. Bring to boiling. While the water is heating up, trim (from the bottom end) of the asparagus to 6″ lengths.
Once the water is boiling, add the asparagus.
Bring back to a boil and then immediately drain and transfer to a bowl of ice water to cool. Drain well.
In a medium pan, combine the vinegar, water, salt and sugar. Bring to a boil.
Remove the jars from the boiling water. Place two teaspoons each of crushed red pepper flakes and dill seed into each hot jar, followed by two sliced garlic cloves and a couple of slices of fresh jalapenos for each jar.
Divide the asparagus between the jars stems facing up. It may help to place the jar on its side to fill.
Ladle the hot vinegar mixture into the jars, leaving 1/2″ headspace at the top. Use a damp paper towel to wipe the rims of the jars clean, then put a hot flat lid and a ring on each jar, adjusting the ring so that it’s just finger-tight.
Return the filled jars to the canning pot, making sure the water covers the jars by at least 1″. Bring to a boil. Boil for 10 minutes to process.
Remove the jars to a folded towel and do not disturb for 12 hours. After one hour, check that the lids have sealed by pressing down on the center of each one. If the lid is dimpled and can be pushed down, it hasn’t sealed and the jar should be refrigerated immediately. Label the sealed jars and store.