Can basil flowers be substituted for basil leaves to make tea?
Yes, you can use them the same way you would use the leaves- note that flowers are often used in herbal tea blends (I see hibiscus used particularly often). Depending on the cultivar, however, the flavor may be noticeably different than what you would get with the leaves, probably a bit more bitter- that's what I noticed when using mint flowers for tea, and mint is very closely related to basil.