In a world where new hydrangeas are seemingly introduced every third week, ‘Tardiva’ (Hydrangea paniculata ‘Tardiva’, above) is a dinosaur. While new, and arguably improved panicled hydrangeas (‘Limelight’, ‘Fire and Ice’, and ‘Little Lime’, below) have been relegated to the far reaches of the garden, ‘Tardiva’ was planted before these newcomers were seedlings in a…