Thai Purple Basil
[Bai Horapha (Thai), Hung Que (Viet), Ocimum basilicum]
Now quite common in Southern California, this basil has good flavor and reasonable keeping properties (almost a week if treated well). In general the leaves are dark green with only a hint of purple, and the stems are distinctly purple but there are also all-green varieties. Of the Asian basils, this one is closest to Italian Basil but is sharper and slightly sweeter in taste. They can substitute for each other in a pinch.
More on Basils.
Buying: Thai Purple Basil can be found in markets catering to a Southeast Asian community. If a little wilted this basil can be refreshed by cutting the stem ends off and immersing completely in cold water for an hour, then dry in your salad spinner.
Growing: Purple basil is more resistant to fusarium wilt than Italian basil but may be somewhat stunted by it.
Storing: If fresh, Thai Purple Basil can be kept loosely bagged in plastic in the refrigerator for about 5 days. Freezing is not a good option because most recipes use it as fresh whole leaves. Dried it's pretty much worthless.
Cooking: The most common way this basil is used is as a garnish or by stirring whole leaves into the recipe after taking off the heat and as close to serving as possible. In either case, before you start cooking, remove the leaves from the stems and set them soaking in cold water. Drain just before adding to the recipe. With this treatment it will take the leaves a few minutes to start to discolor rather than doing so instantly.