Place blueberries in a large stockpot and crush with a potato masher.
Add water and lemon peel; simmer over low heat for 5 minutes. Strain fruit through cheese cloth, metal strainer or food mill to remove pulp and seeds; reserve juice.
In a large saucepan, mix sugar and 4 cups water. Bring to a boil, stirring occasionally, until temperature reaches 260 degrees F (125 degrees C).
Add blueberry juice and boil for 1 minute. Stir in lemon juice and remove from heat.