Photo and description from Johnny's Seeds (www.johnnyseeds.com)
 
The only purple Genovese type basil. Large 2–3" wide, turned-down leaves. This stunning basil is nearly black in color. Ht. 16-20". 
Edible Flowers: Use the flowers in any recipe that calls for basil, or to garnish drinks, salads, soups, pasta, and desserts. Flavor is of intense basil.
 
Harvest: Begin light harvesting after plants have become established. It is best done in the early morning when the temperature is cooler and the leaves are less likely to wilt. A full harvest should be completed just before the plants start to flower. Cut the entire plant 4-6" above the ground to promote a second growth. Leaves are easily bruised when picking, so handle carefully. Do not store at a temperature less than 50°F (10°C).