by Ed Rosenthal
LEDs are lightweight, highly efficient light producers and emit far less heat than HPS lamps. They are also easy to install. The Stealth LED™ grow light has a 50,000 hour lifetime and reduces energy consumption as compared with HPS or MH systems by 60-70%.
LED fixtures cost more than HID lights, but save money in the long run:
•LED lamps use less than half the electricity of HIDs per unit of PAR light produced. At $.10 a kilowatt, LEDs will save $215 per year when compared to the cost of running a 1000w HID twelve hours a day.
•LEDs last longer than HID bulbs.
•LEDs need little to no cooling equipment; HIDs require air or water cooling, ventilation systems, or air conditioners.
Higher quality systems use mostly red light along with some blue. Just as with any other product, manufacturers’ standards differ. A few manufacturers add the green light NASA has shown to be effective with plants, and amber is also sometimes added. Most manufacturers include a few white light emitters in their units. These diodes actually emit a combination of red, green, and blue spectrums, which combine to appear white. White lights help to both supply useful wavelengths for the plants and soften the eerie purple color generated by the combination of red and blue light. Luckily, the spectrum range is usually wider than the band that is guaranteed for each emitter.
Apache Tech LEDs are scientifically designed to enhance plant growth. Red and blue peaks power photosynthesis. Other spectrums required are supplied using white LEDs. The high-output LEDs are very efficient so they save electricity, operate at about 90° F (32° C), eliminating excess heat, and last 50,000 hours for low maintenance. Photo lower left: El Eddy, photo right: Rylar Sonwil
LEDs are powered by either a transformer or a digital driver. Transformers are similar to old-style magnetic ballasts for HID units; they use more energy than digital controllers and produce heat that may need to be dissipated. This is a small consideration compared to the heat HPS lamps produce, which has to be vented. LED lamps emit virtually no heat, so they can be placed very close to the garden and are not encumbered with tubes for air or water cooling, heavy ventilation, or any of the other problems or inconveniences of HID lamps.
Light from LEDs can be combined with HPS and MH lamps, so there is no reason to scrap your digital HID lamp. Adding LEDs to your other lights increases the amount of light delivered to the garden. For instance, a garden using a 400w HPS can be increased to the equivalent of 600 watts using 100 watts of LEDs. Adding 300 watts of LEDs creates the equivalent of a 1000w HID system.
An advantage of using a combination of HPS and LED lights is that you can ensure that you are providing all the spectrums that plants need to thrive. If more HID lamps rather than LEDs are used, they add PAR light, but most of the increase is in the yellow spectrum. Adding red and blue LEDs instead increases PAR light, but not in the yellow spectrum. Excess yellow light forces the plants’ xanthophyll to absorb the heat created by the less useable light falling on the leaf surface. Red and blue LEDs put no additional stress on that pigment. LEDs can be used to amend the light spectrum during flowering. Adding red spectrum during the last half of flowering increases the size and density of the buds and shortens flowering time.
T-5 lights, such as these HID T-5 lights from Amerinada, are the most efficient fluorescent lights available.
LIGHT ACCESSORIES AND LIGHT REFLECTORS
Light doesn’t become weaker or disappear with distance. It appears to dim as the light beam widens over a larger area. As it spreads, its intensity dissipates. Just think of a flashlight. If you can keep the beam tightly focused, it will have the same intensity at the focus point as it had at the point of emission. The larger an area of the garden that a lamp illuminates, the less intense the light that plants receive.
Reflectors are a way to keep the light from your lamps focused where you need it. The three types of lamps discussed—fluorescents, MH, and HPS—all emit light in all directions. Only a portion of the light shines directly on the garden. Unless it is re-directed, the light illuminates wall and ceiling.
Any light emitted by the lamps that doesn’t reach the plants is wasted and might as well not have been produced. There are many solutions, and all but a few involve the use of light reflectors.
FLUORESCENT LIGHT REFLECTORS
The shape of your fluorescent reflector determines, to a great extent, how much light the plants receive. Use the best reflector available. Many fixtures with reflectors place the tubes too close to each other, so that only about 60% of the light is actually transmitted out of the unit. The rest is trapped between the tubes or bounces back and forth between the tubes and the reflector. This light may as well not be emitted, since it is doing no good.
Look for reflectors that have small mini-reflectors or baffles between the tubes. They are angled to reflect the light downward and to separate the light from the different tubes so that it is not lost bouncing between them. These reflectors are available on the Internet if not locally. A good reflector pays for itself over a short period because increased light results in increased yield.
Wing reflectors like this LumeWing by C.A.P. Controllers are designed to guide the heat up to the top of the room and direct light down to the garden.
HPS lamps with air-cooled reflectors are standard lights used for commercial marijuana gardens. Reflectors are essential in maximizing the efficiency of your lamps. The light is directed to the canopy rather than the ceiling, floors, and walls. Lumenaire by C.A.P. Controllers reflectors fit a variety of bulbs.
Like other fluorescents, CFL bulbs emit light in all directions. Inexpensive clamp-on fixtures with bowl reflectors help direct the light to the garden. Commercial reflectors are available for larger size CFLs. Good reflectors can double the light intensity the garden receives from CFLs.
MH AND HPS REFLECTORS
Both MH and HPS bulbs emit most of the light along their length, so it comes out of the sides of the bulb. Many fixtures orient the bulb horizontally to take advantage of this. The reflector must direct the rest of the light downward.
There are many reflector models, but they can be classified into two general types, depending on which position the bulb is held, horizontally or vertically. For most gardens, horizontally held lamps are preferred.
HORIZONTAL REFLECTORS
Horizontal lamps deliver more light directly to the garden because of the position of the bulb and the direction that light is emitted. Manufacturers have created many designs and each leaves its own illumination footprint. Some focus light in a small area; others are designed to distribute it over a large space. The best reflector for a particular garden depends on the garden’s dimensions and design.
Small one-light or two-light gardens do better with focused reflectors. The light is directed downward, so most of it goes directly to the garden. Focused beam reflectors minimize the light that goes off to the sides. Larger gardens grow more vigorously when the reflectors in the center spread the light over a larger area. The plants receive light coming from different directions, minimizing shadows and giving a larger portion of the plant the opportunity to actively photosynthesize. Reflectors closer to the perimeter should still be close focused so that light remains in the garden.
Tube reflectors spread the light over a wide area and are especially useful in large gardens. They can also be positioned vertically in Coliseum type gardens.
Tube reflectors are very convenient in a large garden because they spread the light over a wide area. When used together, they diffuse light in many directions, reducing the amount of foliage in shadow.
VERTICAL REFLECTORS
When a bulb is held vertically, almost all of the light comes out the side and follows a horizontal path to the walls. This light must be directed down to the garden. None of the commercial vertical reflectors I have seen are well designed. The light they redirect is broadcast over a very wide area. Some reflectors have adjustable bulb positioning so the light is controlled somewhat, but most reflectors ar
e too shallow and miss a large portion of light, so it is lost to the garden. Because of their poor design, vertical reflectors are very inefficient at directing light to the garden.
AIR-COOLED LIGHTS
MH and HPS lamps emit a lot of heat. You should figure each 1,000 watts of light input creates about 3,414 BTUs of heat. Just three of these lamps release the same amount of heat as two electric space heaters. If all of this heat is released into a room temperature garden, it has to be removed either through ventilation or air-cooling.
Air-cooled light reflectors solve part of the problem by removing the hot air before it gets into the room. The fixtures have a bottom glass so the lamp is totally enclosed. A six- or eight-inch inline fan is attached to a six- or eight-inch accordion air hose outside of the garden area. It leads to a small pipe extending from one of the short sides of the reflector and supplies it with cool air. Another hose attached to the other side of the reflector leads out of the room. The cooling air travels through the tube and never has contact with the air in the garden. It picks up the lamps’ heat but absolutely no odor from the room. The air can be safely exhausted from the structure or used to heat interior space.
Depending on the quality of the air-cooled reflector, between 60 and 90% of the lamp’s heat is removed from the room, simplifying temperature management. The one problem with air-cooled lights is that the bottom glass in the fixture absorbs UV-B light and 8% of other spectrums, so the advantage of using MH lamps is eliminated.
Another strategy is to use air-cooled lights with no enclosing glass. Air is drawn from the garden space through the tubing and then cleaned of odor using an in-line carbon filter so it can be exhausted or used for heating. Air above the canopy is pulled up into the reflector, drawing the heat with it. This keeps the canopy cool.
WATER-COOLED REFLECTORS
Water-cooled reflectors work in much the same way as air-cooled reflectors except that, instead of air, water is used. The water is circulated in a closed system in which the water flows across the hot glass of the bulb and is cooled outside the garden. The water exchanges virtually all the heat the lamp emits and then removes it from the room.
There is a natural aversion to the thought of mixing electricity and water. Put those thoughts aside. The water moving inside the tube touches only the glass portion of the bulb. These systems have been available commercially for many years. I have never heard first hand of an accident occurring with them, and the manufacturers are still in business, which also attests to their safety.
The water absorbs about 10% of the light. Unfortunately, more than 10% of the red light is removed because it is the weakest and is absorbed first. UVB light passes through the water, but not the glass.
Air-cooled lights make it easy to keep the garden cool. The circulating air is odorless, so it can be used to heat other areas.
This air-cooled reflector removes most of the heat emitted from the lamp. The lamp produces a lot of heat, about 3400 BTU’s.
LIGHT MOVERS
No matter what kind of light reflector you use, it delivers light in an uneven pattern. Usually the center area, directly under the lamp, receives the most light. The intensity of the light tapers off as the distance from the center increases. Moving the lights helps eliminate differences in light intensity. Light shuttles move metal halide and sodium vapor lamps so that the angle of light changes. As the lamps move, each plant section comes directly under the light repeatedly. Instead of plants in the center receiving more light than those on the edge, the light is distributed more equally throughout the garden.
Water-cooled lights and reflectors allow the grower to maximize the light available to the canopy without over-heating the room or burning the plants. They are safe because water never comes in contact with the current. The Fresca Sol light above removes 93% of the heat created by the bulb. From the light, the water goes to a reservoir and sometimes to a heat exchanger located outside of the garden space. After the water is cooled it recirculates back to the lights. With a large enough reservoir such as a hot tub, you can easily cool 8 lamps.
The water removes so much heat that you can touch the reflector without discomfort.
These units increase the efficiency of the light and garden in several ways:
Moving lamps distribute light evenly, so there are no hot spots to create uneven growth. With movers, plants grow more uniformly. Clones from a single variety grow to the same size and ripen at the same time.
Lights can be placed closer to the plants so they receive more intense light with less directed outside the plant area.
Total garden growth and yield increases. Getting light to the formerly light-deprived areas of the garden increases their growth more than less light decreases growth in the formerly favored sections. Expect a 10-20% increase in yield using light movers.
Shuttles move lights in one of two ways. Linear models move lights back and forth in a straight line. Circular models move the lights in an arc.
Linear movers have a standard-issue 6-foot movement area. However, some models have shorter lengths, and the distance they travel can be adjusted. Even if you’re only moving a single light one foot, the angle of light to the plant changes. Areas that were in constant shadow see the light and respond with increased growth.
Using accessories, light movers can move several fixtures at the same time. The accordion tubing attached to air-cooled lights moves with them.
Lamp movers that travel in a circle are convenient to use with gardens that are square. Some revolve the lights in one direction and then re-trace the journey. Most of these can be used with air-cooled lights. Rotating movers perform the same function as the linear movers, providing an even source of light throughout the garden.
Spinners are light movers that rotate lights much faster than other light movers. They come in various sizes and hold one to four lamps. Because of the fast speed at which they spin, plants receive a more continuous blast of light. Since the increased airflow generated by the spinning keeps the lamps cooler, the whole unit can be lowered closer to the plants. Although the lamps stay cool, the lamps still spread the heat they emit throughout the room.
Choose a light mover model that is appropriate to use in your garden—linear for a rectangular space, rotating for a square or circular one.
PHOTOPERIODISM IN MARIJUANA
The term short-day is something of a misnomer; what marijuana needs is a sufficiently long night.
Marijuana flowers only if it has been kept in the dark for at least 9-11.5 hours depending on variety, this critical light period occurs for 5-7 days consecutively.
The lights travel in a circle revolving about 270˚ in one direction and then traveling back. Three to five lights can be attached, depending on model. This system is an excellent choice for square gardens that are 8’ x 8’ (240 x 240 cm).
This light mover carries the lamp back and forth over a fixed length, usually 5-6’ (152-162 cm). Photo: SeeMoreBuds
Interruption of an otherwise long night by red light (666 nm) prevents flowering unless it is followed by irradiation with far-red (730 nm) light.
An intense exposure to far-red light at the start of the night reduces the dark requirement by two hours. These responses are mediated by phytochrome.
Phytochromes exist in two interconvertible forms—
•Pr because it absorbs red (R; 660 nm) light;
•Pfr because it absorbs far-red (FR; 730 nm) light.
These are the relationships:
•Absorption of red light by Pr converts it into Pfr.
•Absorption of far-red light by Pfr converts it into Pr.
•In the dark, Pfr spontaneously converts back to Pr over a two hour time period.
•Sunlight is richer in red (660 nm) than far-red (730 nm) light, so at sundown all the phytochrome is Pfr.
•During the night, the Pfr converts back to Pr.
•The Pr form is needed for the release of the flowering signal.
Therefore, mari
juana needs 9-11.5 hours of darkness for several days of this regimen in which it converts the Pfr present at sundown into Pr to carry out the supplementary reactions leading to the release of the flowering signal.
If this process is interrupted by a flash of 660 nm light, the Pr is immediately reconverted to Pfr and the night’s work is undone.
A subsequent exposure to far-red (730 nm) light converts the pigment back to Pr and the steps leading to the release of “florigen” can be completed.
Exposure to intense far-red light at the beginning of the night sets the clock ahead about two hours or so by eliminating the need for the spontaneous conversion of Pfr.
MANGO
CARBON DIOXIDE
CARBON DIOXIDE (CO2) is a gas which comprises about 0.038% or 380 parts per million (ppm) of the earth’s atmosphere.
CO2 is one of the two raw materials required for plant photosynthesis. (Water is the other.)
Cannabis uses CO2 only in the presence of light. Photosynthesis occurs immediately after the plant receives light. The plant starts mining CO2 from the air by opening its stomata, tiny organs found on the leaf surface, primarily on the underside. They function much like pores in the skin. They regulate the absorption of water, gas, oxygen, (O2), and CO2 into the plant, as well as the evacuation of water and O2 from the plant.