Place the dried flowers in a large glass measuring jug. Zest the lemons and add it to the jug, then the citric acid and lemon juice. Bring the sugar and water to a boil, stirring occasionally to dissolve. Let the syrup cool enough so that you can stick your finger in it without getting burned; you can leave it to cool to room temperature, too. Pour the syrup over the flowers, lemons et al and stir to combine. Cover the jug or bucket with a towel and leave it for 2-4 days. When you are ready, strain it through a fine-meshed sieve lined with cheesecloth or a paper towel into a clean Mason jar. Seal the jar and store in the fridge. To serve, pour 1-3 tablespoons of the syrup into a pint glass and add water or seltzer. Or you can add a tablespoon to a glass of sparkling wine, or to a couple shots of vodka or gin.
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