Lighting question...

New to site. Please correct me if I am posting incorrectly.

Currently have my trees growing indoors, under a 600W MH/HPS system. First two wks I have timer set for 20/4. Each wk there after I plan to drop an hour until I reach 12/12 (9wks) of veg. state. Any comments on this?

Question is, at what wk shall I change lamp to HPS. Do I change when I reach 12/12 or is it more beneficial to switch earlier, say at 15/9 or 14/10?

Thx for any comments.

Just switch, insatntly your MH at 20/4 then, HPS 12/12.

use MH for VEG stage wich is 18/6 cuz i mimics the long days of summertime and use your HPS druing flower stage witch is 12/12 cuz that mimics the shot days of fall when marijuana loves to throw those beautiful flowers

The best way would be to wait until your plants have gone through the 'stretching period', and then make the switch. The MH will minimize stretching, and keep the internodes tighter than the HPS.

Switch to HPS at 12/12 it is, thx.