In a bowl mix together the cooked quinoa, peaches, blueberries, arugula, and mint. Mix. Divide between plates and sprinkle with the pistachios.
To make the dressing, slightly crush the lavender buds with your fingers and place them in a little bowl. Add the oil and vinegar and let stand 15 minutes. Strain and discard the lavender flowers. Stir in the blackberries and slightly mash them with a fork or spoon. Season with the salt. Try and add the maple syrup if desired.