Wash quart-sized glass jars and lids thoroughly to ensure they are clean and sterile.

Trim the asparagus to fit into the jars, aiming to leave about 1 inch of headspace below the rim.

Bring a pot of water to a rolling boil and blanch the asparagus for 2 minutes, then immediately drain.

In a medium saucepan, combine white vinegar, water, granulated sugar, salt, garlic, black peppercorns, red pepper flakes, and dill seeds and bring to a rolling boil over high heat to dissolve sugar and salt.

Pack the blanched asparagus tightly into the prepared jars, arranging them upright.

Carefully pour the hot pickling liquid over the asparagus, leaving 1/2 inch of headspace at the top of each jar.

Wipe the rims of the jars clean with a damp cloth and seal securely with lids.

Allow the jars to cool to room temperature, then refrigerate for at least 24 hours before serving for optimal flavor.