Ocimum Basilicum:A cultivar of Sweet Basil referred to as Opal Basil. Origin: Opal Basil is a basil cultivar developed at the University of Connecticut in the 1950s. Appearance: With its distintive deep violet color, opal basil has crinkly and serrated leaves with similar colored veins and stems. Taste: Opal basil is more savory than sweet compared to common basil. Flavors of clove and ginger are revealed when eaten raw.