‘Dark Opal’ Basil (Ocimum basilicum 'Dark Opal') offers dark purple, almost black leaves that are perfect for celebrating Halloween. Bonus? The edible leaves have a unique licorice flavor that can be incorporated into many culinary dishes when you're finished with your spooky season decorations! While ‘Dark Opal’ Basil does take some work to cultivate, we think this tasty and visually striking plant is worth the effort. ‘Dark Opal’ Basil does best in full sun and is grown as an annual.