Black light

ok i have 3 question about blacklight & growing.
1. how would a blacklight effect the plant??
2. what stage would you do it in if any?
3. when would i do it during my daylight hours or after i turn them off?

1. it helps the plant during flowering. giving extra spectrum of light.
2. only during flowering. but you could do it all through the gowing stage.
3. only when the lights are on. not at night.

give it a go more light the better.