Cover petals with lemon juice in a deep glass bowl. Microwave for two minutes on HIGH.
Mix sugar and boiling water in a saucepan, heat over high heat on stove top until boiling and sugar is thoroughly dissolved. Add the petals and lemon juice mixture to the sugar water. Stir well. Simmer over medium heat until reduced by 1/3 volume (approximately one hour).
Strain to remove petals, then store in a covered jar in refrigerator. Syrup keeps for a year and is delicious over fresh fruit, ice-cream, custard, pound cake, etc.