Time To Chop?

[Volker]

When is the right time to cut a plant down?

When 50%-75% of the pistils have turned brown. Or, if you're Mr. Wizard, when the trichomes are to your liking. No fixed time.

Is there an average amount of ounces each plant should produce?

Depends on light, nutrients, care, time, patience, experience, etc.

How long would a plant take to grow from germination to harvest?

Depends on strain. 90 days start to finish is a general rule of thumb, but can take anywhere from 6 weeks to 16 weeks.