Herbacious plants can be safely pruned by removing about 1/3 of the foliage .
If you were to prune 50% of the foliage or more , the plant goes through "shock" , and is 'set back' a bit .
Wherever you prune close to a leave or stem , it will double the leaf or stem production .
Once my sweet basil goes into flowering and into seed production, it is extremely difficult to prevent it continueing.
Well I pruned off way more than 50%. It was the last whack that did it. I got distracted and missed the target and lopped off a bunch more than I had anticipated. LOL