400W bulb... 5 plants... How tall?

[southpawprof]

I'm trying to decide when to switch over to flowering. I have a 400w metal halide bulb with a decent reflector, and some mylar on the walls. I have 5 white widow plants, and I want to maximize the 400 watts without going overboard (I don't want the plants to get so big that the light can't handle the task anymore.) I assume they will roughly double in size during flowering... so given my lighting setup, at what height should I start to flower?

 

[Cr8z13]

Not sure how others will feel, but I think 2.5-3ft is as tall as I'd want to grow a plant with a 400 due to light penetration concerns. You could maximize yield by using SCROG or supercropping.

 

[smokinskins]

since you got the right start invest in the hps bulb for your unit if you have the proper ballast that can run both types. i dont know it it could handle 3 footers! maybe but you might want to top them and tie down branches, this will allow it to get more light on more surface area. mine are about one and a half foot now, flowering with the 400w. you could go a bit taller but i love the branch tie down thing- so much more surface area and my plants arent streching as bad as they told me after that 12/12 switch

 

[southpawprof]

since you got the right start invest in the hps bulb for your unit if you have the proper ballast that can run both types. i dont know it it could handle 3 footers! maybe but you might want to top them and tie down branches, this will allow it to get more light on more surface area. mine are about one and a half foot now, flowering with the 400w. you could go a bit taller but i love the branch tie down thing- so much more surface area and my plants arent streching as bad as they told me after that 12/12 switch

My ballast is meant for an hps bulb, right now I'm using a MH conversion bulb... I have a 400 HPS for later . So maybe I should shoot for 30"-36" plants. I'm a little nervous about the tie down thing... how do you tie the branches down, and when do you start that? Right now I'm only 2 weeks into veg.

 

[smokinskins]

My ballast is meant for an hps bulb, right now I'm using a MH conversion bulb... I have a 400 HPS for later . So maybe I should shoot for 30"-36" plants. I'm a little nervous about the tie down thing... how do you tie the branches down, and when do you start that? Right now I'm only 2 weeks into veg.

they will strech with the switch so plan on it, but i topped mine and its the best thing i ever did! branches- not sun leaf stems will grow like crazy. i have some thread taped to the pot thats it! branching will promote alternate branching as they try to get light from under the sun leaf and twist. i did mine one at a time when they reached up to the canopy from top to bottom to allow light to penatrate the plant in the center, down to the lower levels. all of a sudden its a bush not a stick! topping will make branches, tie down when they reach the top or if you want to move it out of the way to let other spots share light. i topped anywhere between 4th and 6th node and those plants have major more bud than the one i left alone!