Step 1In a small saucepan, whisk the water and sugar over high heat until the sugar is in suspension and no longer mounded on the bottom of the pan. Bring the mixture to a boil and cook until all of the sugar is dissolved, about 5 minutes. If this happens before the water boils, heat to the boil anyway.
Step 2When the water comes to a boil, remove the pan from the heat and add the rose geranium leaves. Let the mixture steep at least 10 minutes while you're slicing the nectarines.
Step 3Combine the nectarines and blackberries in a large bowl or divide evenly among 6 small ones. Ladle the warm syrup through a strainer over the fruit. This can be done up to 2 hours in advance and held at room temperature until serving.
Here are some pairings of flavored syrups and the fruits they best enliven. Follow the directions in the recipe for nectarines and blackberries with rose geranium syrup, substituting herbs and fruits as follows.
Basil: 2 tablespoons chopped fresh leaves. Pair with cherries, strawberries, figs
Black peppercorns: 1 teaspoon crushed -- not ground -- black peppercorns. Pair with cherries, figs, blackberries
Chamomile: 1/2 teaspoon powdered chamomile tea, made with all flowers only. Pair with cherries, blackberries
Jasmine: 1 teaspoon jasmine pearl tea. Pair with cherries, figs, blackberries
Lemon verbena: 2 tablespoons chopped fresh leaves. Pair with figs
Mabel Grey geranium: 2 tablespoons chopped fresh leaves. Pair with figs
Rose geranium: 2 tablespoons chopped fresh leaves. Pair with nectarines, peaches