Cut or pull blossoms from the stem. Rinse and dry well, removing any leaves, stems, or brown flowers.
Add blossoms and sugar to a bowl*. Stir to combine. Add the sugar mixture to a jar, put the lid on, and shake the jar to distribute the flowers.
Shake the jar at least once daily for 7 days.
Sift to remove the dried blossoms**. Store in a jar. If the sugar is slightly damp, dry if desired by baking on a parchment-lined tray for 5-10 minutes at 200°F. Cool, break up any lumps, and store.
Notes
*Alternatively, to save a dirty bowl, add about ⅛ cup sugar to a 2 cup jar. Add ⅛ cup lilacs. Alternate sugar and lilacs until both are used or the jar is filled. Put the lid on and shake the jar to distribute the flowers. Continue with the recipe as written.**Lilac sugar, with the blossoms, can be blended in a food processor. This will make a lovely, stronger flavored sugar.