Bring a boiling-water canner, half full with water, to simmer. Enough water to cover the jars by 1-2 inches. Wash jars and screw bands in hot soapy water; rinse with warm water. Or dishwasher and keep hot. Pour boiling water over flat lids in saucepan off the heat. Let stand in hot water until ready to use. Drain well before filling.
Place chopped lemon verbena leaves and water into a pan. Bring it to a boil, then take it off the heat and let it steep, covered, for 15 minutes.
Place apple juice in a quart size measuring cup.
Strain and add infusion to juice to make 4 cups (adding more water or juice to if needed). Place in a 3 1/2-quart or larger saucepan. Add lemon and sugar. Mix well and bring to a full boil over high heat, stirring constantly.Add the liquid pectin; bring back to a full rolling boil and boil for exactly 1 minute.
Ladle immediately into prepared jars, filling to within 1/8 inch of tops. Wipe jar rims and threads. Cover with two-piece lids. Screw bands tightly. Place jars on elevated rack in canner. Lower rack into canner. (Water must cover jars by 1 to 2 inches. Add boiling water, if necessary.) Cover; bring water to gentle boil. Process 10 minute Remove jars and place upright on towel to cool completely. After jars cool, check seals by pressing middle of lid with finger. (If lid springs back, lid is not sealed and refrigeration is necessary.).
Sealed jars can be store up to one year in a cool dark pantry.