African Blue basil is the plant I was referring to, it is a cross of 2 basils, and in honesty, I could not tell you exactly how to split hairs on designating what a technical term for layering new plants from last years plants would be.
I do not always succeed in keeping cuttings alive past Feb where I am.
As far as turning black, that would be considered freezer burn, it is a tender plant after all. Even dried herbs lose their flavor within a year or less.
IF you have seeds, and a good indoor place to grow them, then simply reseed until you can harvest. Basil can be successfully be a (ummm, lost my word) succession planting crop. African blue basil:
African blue basil (Ocimum kilimandscharicum × 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.
Ocimum kilimandscharicum × Ocimum basilicum
Peter Borchard, Companion Plants, Athens, Ohio, 1983[1
I should have edited this earlier