| African blue basil | |
| Hybrid: | Ocimum kilimandscharicum Ă Ocimum basilicum |
| Cultivar: | 'Dark Opal' |
| Origin: | Peter Borchard, Companion Plants, Athens, Ohio, 1983 |
African blue basil (Ocimum kilimandscharicum Ă basilicum 'Dark Opal') is a hybrid basil variety, a cross between camphor basil and dark opal basil. It is one of a few types of basil that are perennial. African blue basil plants are sterile, unable to produce seeds of their own, and can only be propagated by cuttings.[1]
This particular breed of basil has a strong camphor scent, inherited from Ocimum kilimandscharicum (camphor basil),[2] its East African parent. The concentration of camphor is 22% (compared with 61% for O. kilimandscharicum). The concentration of the other major aroma compounds, linalool (55%), and 1,8-cineole (15%) is comparable to many basil cultivars.[3]
All parts of the flower, leaves, and stems are inedible because of the high concentration of camphor. In adults, consuming 2g of camphor usually causes toxic effects and 4g can be potentially lethal.[4]
The leaves of African blue basil start out purple when young, only growing green as the given leaf grows to its full size, and even then retaining purple veins. Based on other purple basils, the color is from anthocyanins, especially cyanidin-3-(di-p-coumarylglucoside)-5-glucoside, but also other cyanidin-based and peonidin-based compounds.[3]
It blooms profusely like an annual, but being sterile can never go to seed. It is also taller than many basil cultivars. These blooms are very good at attracting bees and other pollinators.