Hey bongzilla, there is not a given time frame on how long you will need to wait. Care to give us some more info on your grow?
1. Soil or Hydro?
2. If hydro what type bubble, ebb and flo, etc.?
3. ferts/nutes used? Soil mix?
4. Lighting: Florous, HPS, MH, or mix? wattages?
5. PH if known...