Vertical HPS. It's a 4'x4'x6' box on 6" legs. Two 600w bulbs hang inline down the middle of the box. There is a floor fan at the bottom blowing straight up over the bulbs, air-cooling them, and an extractor fan above pulling the air out (which you can see in the photo). A cylindrical trellis is wrapped around the bulbs and fans, and the plants are grown around the outside - up to eight at a time.
The plants are grown in 2-gallon pots of coco that are auto fed by drippers on timers. The waste nutrient drains out the bottom and out into a vege garden outside - that's why the box is on legs, so the plumbing hoses (nutrient inlet, waste outlet) can enter and exit underneath. There's a hole in the bottom of the box, which also lets in fresh air and keeps light leaks to a minimum.
You'll notice the plants are not typically top-heavy - they grow bushy on all sides because they have complete side-lighting. You get much more yield for the same height, and no wasted light, as the bulbs are completely surrounded by plants.
It's a great way to grow tall sativas, as you can see below. But I also like to grow a bit of variety, so I didn't always maximise my space., and always had various height plants in there.
I've never really liked horizontal HPS set-ups, as most of the light is reflected off the hoods, which probably only have 80% efficiency, and heat is trapped underneath. With vertical growing, no light is reflected and all the heat is ducted away. It's also a good use of a small footprint, as you are obviously growing vertically.
There are two reasons why the big room I designed has horizontal HPS lamps. Firstly, my mate was skeptical of LEDs and wanted to use HPS. "Fair enough" I said. He then wanted to grow vertically, like me. But I said that eventually he would come around to LED and that it would be easier to covert if we set the grow up initially as a horizontal grow.
Horizontal grows are a little less work than vertical, as you need to do a lot of plant maintenance to ensure they grow around the light and fill in all the gaps.
Here are some other old grows that were different to the previous one I posted. They weren't alway 3.5lb - depending on strain (I always multi-cropped) - but the best I had was close to 4lb (60oz) in that 4x4, growing a bunch of haze plants similar to the one below.
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