reg

OldBasilisk

Not my exact method, but good info. By SCW back in the day.

This article is intended to provide information for new growers using the ``ScrOG’’ or ``Screen of Green’’ method in mini or micro cabinets under small HPS lights, in the range of 70 to 250 watts. I won’t discuss the application at 400, 600 and 1000 watts, as that’s outside the scope of my experience. Refer to Iguana’s site and others for information on what is called production scrog.

Small HPS lights
Small HPS lights are perfect for growing cannabis in restricted space conditions, as they produce the most light from a given amount of electricity of any suitable lamp for cultivation, and produce a spectrum that is favorable for flower growth. The spectrum is not the best for vegetative growth, but that isn’t really important to scrog growing, as the vegetative period is so short. Lights as small as 35 watts are available by stripping components from security lights commonly available at discount hardware stores. 250 watt lights can produce as much per foot in scrog conditions as 1000 watt lights in room growing. A single 70 watt light can produce enough for an average pot smoker in a space as small as 1 sq. ft. MH lights are available in small sizes, but they produce less light and more heat than their HPS counterparts, and heat is an important consideration in cabinet-style growing. Regarding fluorescents, the light to heat ratio is even worse, and I am not aware of any situation in micro and mini growing where I would favor them over small HPS lights.
Note that these lights are quite weak compared to 400, 600 or 1000 watt lights used in production growing. I read a post recently on ADPC where the question was raised whether two smaller HPS lights were equal to one HPS light with the same total wattage. The answer is no, and the reason is intensity. Consider a stream of water coming from a bunch of garden hoses at normal pressure. You could stand in front of them, right? You’d be wet, but they wouldn’t knock you down. Now how about the same volume blasting you in the gut from the nozzle of a fire hose? You’re on your butt. Replace the fire hose in the example with a 1000 watt light and a group of 70 watt lights for the bundle of garden hoses, and you get the picture. Intensity means that the light can be father away from the plant and still be bright enough at the bud surface to produce. Intensity is necessary for tight bud formation.
To get the most out of a small HPS light, you must keep the bud sites within the productive range of the bulb, a lopsided sphere extending out from the lamp source. For a 250 watt light, that circle of light extends out about 20-24" from the lamp. For a 70 watt light, the maximum distance is apparently around 8" (per chthonic, who has experience with the lights). A group of tall, skinny plants under such a light would only be properly lit at the very tops of the plants, leaving the bottom parts shaded out and in a low intensity light field, producing small, lightweight buds at best. Ideally you would like all the buds within that magic circle of light intensity, and you would like that sphere of light completely filled with buds. How can that be accomplished?

The scrog method
The essential detail of the scrog method is a screen, usually poultry netting, typically suspended between the planting medium and the lamp. The plants grow up to the screen and then are ``trained’’ under the screen, resulting in a flat table of plant growth, a field rather than a forest. Because all the buds are growing at the same height, it is possible to get all the growth within the effective circle of light from the lamp, maximizing production from the space. It’s really that simple.
Well, nothing new under the sun, the method has been used for years. In modern terms, the method was first popularized on the internet by the work of pH on the usenet group Alt Drugs Pot Cultivation, or ``ADPC’’ for short. You can access ADPC from several web-based sources, and pH still posts there regularly. But the method as initially used by pH was designed to tweak production from a large area under fluorescent lights, like the ``multi-shelf’’ method explained in his article on N.P. Kaye’s Lycaeum site. N.P. Kaye is in fact credited with the term ``screen of green’’, which pH shortened to ``ScrOG’’.
I am aware of a least one grower who used scrog and HID lights before that time, based on a mention in Robert Clarke’s book ``Marijuana Botany’’, which was also a source for pH. But most work involving scrog and HID lights is quite recent. It is noted by pH that the first ``yield-o-rama’’ post involving scrog with HID lights was in July of 1997.
Before discussing the method in detail, let’s explore the other alternative for small HPS lights, the sea of green method.

Sea of green
The sea of green method was developed to maximize the speed of cannabis growing in limited height situations. In a typical sea of green setup, clones are planted at densities as high as 9 per sq. ft. Within a short time after being established, the lights are switched to a 12 hour dark period. What happens to the planted clone?
The clone could just sit there, stretch a bit under the light regime, and flower, producing a tiny little bud with a couple of seeds. But that never happens. Instead the clone takes off in a rush of growth, forming a woody main stem and branches. If the plant is suitable for sea of green growing, it will stop short of the lights and flower. Most indica dominated plants stop short enough to be grown using this method. That process is at the heart of the sea of green method, as it results in the smallest possible plant flowering in the quickest possible time.
Why does the clone act in this manner? The actual process is subject to debate. Your author suspects that the clone reads the light switch as fall, and has a mechanism that recognizes that it’s too small to produce seed. So the clone goes into a furious growth mode that stops when the plant reaches a minimum height set within its genetic software, and then flowers. Others argue that the clone’s response is just a variation on the normal stretching process that happens when flowering is forced in any size plant. For purposes of the discussion here, it doesn’t really matter why the response occurs, just that you can rely on it.
The problem with the sea of green method under small HPS lamps is that it produces a number of small spikes under the lamp, a forest rather than a field. The plants crowd each other out and shade the lower portions, which in any event are too far from the light source. As we discussed above, tall and skinny is not productive under a small light. I grew initially using this method, based on books and magazines that I read before designing my 250 watt system, and it worked well for many years, yielding just over 1 oz. per ft. Not bad, but it can be so much better.

Basic flat, fast scrog
The screen method used by pH relied on a long vegetative period for the plants to cover a large area of screen held close to a series of fluorescent tubes. The method I will describe here uses the same sort of growth process that occurs in a sea of green plant, and is very fast.
The screen should be set about 8-12" above the planting medium. There are two purposes for that gap. First, you have to get your hands underneath the screen in order to handle the plant shoots and to remove excess growth shaded out under the screen. Second, there needs to be sufficient space for the plant to branch. Branching is essential to scrog. I prefer a space of about 10" for a 250 watt light, but some growers prefer shorter gaps for smaller lights, as little as 4-6".
Note that the screen does not have to be absolutely flat, and there are good arguments for dishing the screen to match the curvature of the light field. I don’t radically dish my screen, but I do tie down the middle of the screen to prevent the screen from being pushed up, which would be counter productive.
The clones are set under the screen at a density of about 1 pla