Place the elderflowers in a medium, heavy-bottomed sauce pot. Cover with the water and bring to a boil. Let simmer, covered, for 30 minutes.

Remove the pot from the stove and strain the liquid into a fine mesh strainer into a bowl. Discard the flowers.

In the same sauce pot add the sugar. Whisk the liquid back into the pot with the sugar.

Bring to a simmer for 10 minutes more. Remove from the heat and, using a funnel and a ladle, pour it into mason jars to store in the refrigerator. Use as a flavoring for spritzers or as a delicate flavoring for oatmeal, yogurt and other favorite things.