Light deprivation, or “depping,” is a technique used by growers to maximize yield by manipulating light exposure to mimic light conditions that occur in the fall, which forces plants to flower.
If you’re new to depping, you may want to review Americover’s intro to light deprivation before digging into the advanced tips below. For those already familiar with depping techniques, check out the following ten expert tips for growers that want to:
- Multiply annual harvest yield
- Grow stronger/healthier plants
- Increase profits
Let’s get started:
1. Research marijuana strains thoroughly
By researching different strains, you gain critical information about sun exposure, when to plant and harvest, and vulnerabilities that could limit overall production.
Vulnerable strains include those most susceptible to mites, mildew, mold, root rot, and fertilizer sensitivities. Some of the more delicate strains include OG Kush, Pure Kush, Bubba’s Gift, and Guido.
As you work through a few harvests, you’ll develop experience that will allow you to tackle more sensitive strains. James Defenbaugh advises “what you need to do is choose a strain, and master that strain. Figure out what it needs, how long it takes to flower, and how to reproduce those results.”
Whatever strain you decide to work with, make sure to note ideal sun exposure and daily darkness minimums. This will vary depending on the plant type and whether it’s an eight-week or ten-week strain.
2. Make a grow schedule and stick to it
To be effective, growers maximize the sun but shoot for a consistent light-dep schedule of twelve consecutive hours of unobstructed darkness for sixty days. Exactly how they accomplish this varies.
The old-school camp favors a sun exposure between 7:00 a.m. and 7:00 p.m., setting a hypothetical greenhouse covering time at 7:00 p.m. and uncovering at 7:00 a.m. This method is contingent upon good ventilation throughout the whole grow, especially during the bud cycle.
James Defenbaugh, author of The Light Dep Growers Guide: How to Harvest Marijuana Multiple Times a Year, says that the “ideal time to cover is when the plants are getting shaded out.” But he goes on to say that growers must also consider location, orientation to the sun, and personal schedule and flexibility. Plants, especially once budded, need to be uncovered at night to ensure proper air circulation and temperature.
Defenbaugh’s bottom line is to simplify: if the best light is from 6:00 a.m. to 8:00 p.m., you may want to use the morning hours to light-dep, so your plants don’t get cooked in the evening heat.
While a lot of people rely on the default 6:00 p.m. to 10:00 p.m. cover window that produces nice sticky buds, you have to figure out what schedule works best in your locale’s light, temperature, and humidity conditions. If that means covering at 5:00 p.m. and uncovering once it’s dark to let your plants awaken naturally when you do, so be it. If you’re in a hurry, you might cover at 6:00 p.m. and with a lot of ventilation, not uncover the plants until 7:00 a.m., shortening the duration 3 to 4 weeks. Once you find your schedule, follow it.
Light dep occurs within a broader context of controlling environmental factors like temperature, humidity, irrigation, and CO2 levels. It is essential to ventilate your grow, which will provide circulation, humidity and temperature control, and manage the CO2/Oxygen replacement. Ventilation removes warm, humid air and replaces it with drier air to prevent condensation, the breeding place for disease and mold. Moreover, proper airflow also creates a balanced environment for optimum photosynthesis. Good air flow means plants will have the necessary CO2 to produce food sugars for maximum growth.
Depending on the size of your grow, you may use passive ventilation by venting or mechanical ventilation by installing exhaust fans or other mechanical devices that control air circulation. Because air circulation interacts in complex ways with other factors that are difficult to manage manually, most growers turn to automation. In fact, according to Cannabis Business Times’ 2016 “State of Industry Report,” more than two-thirds of cultivators reported using automated temperature control, and half said they controlled humidity with technology.
Covering and uncovering a greenhouse is no small task, but it’s made a lot easier with equipment that helps automate some of the process.
The BOLD® EZarm allows one person to easily cover and uncover a greenhouse in just minutes. Unlike other arms, this product is mounted to concrete and specially designed to withstand extreme outdoor conditions.
Regardless the type of automation you decide to employ, each demands a capital investment. Fully automated systems require a substantially greater financial investment. That means that when you decide on automation, make sure you’re adding an investment that frees up your labor to do more important tasks. If you can cover and uncover plants in minutes, you will have “more time to work on optimizing everything else.”
5. Avoid light leaks
Light leaks occur when sunlight penetrates a greenhouse cover either because of pinholes, rips and tears, or poor fit. During the light deprivation cycle, any amount of light can trigger plants to prematurely flower.
To avoid light leaks, look for a greenhouse cover that’s designed specifically for light-dep and delivers total blackout protection.
BOLD® (Black Out Light Deprivation) is the #1 requested light-dep cover in the country and features a built-in scrim reinforcement that adds durability and tear strength to ensure no light leaks. BOLD® is made of virgin polyethylene, so it’s safe to use with all agricultural products, and carbon black blocks light, and UV inhibitors extend the life of the polyethylene. BOLD® puts you in control of the sun, so you can protect your valuable plants with controlled sunlight exposure.
6. Encourage better vegetative growth
Vegetative growth is essential to maximizing harvest yields. During the vegetative growth stage, the plant needs to get bigger, or stretch, to generate sites where the buds will grow. Too few of these sites will limit production; too many, and growth may overcrowd the greenhouse.
If you follow tip #1 and research your strain thoroughly, you will know how big the plant should be before the flowering stage.
7. Trim in some light
After the pre-flowering stage, some growers prefer to trim or prune parts of the plant that will not produce quality flower, because they are too shaded by large leaves near the top.
By cutting off branches that are not essential or shading parts of the plant you want exposed to the sun, you can control the size and quality of other flowering sites. The reason this technique is successful is because the plant redirects energy once flowering has begun. If less productive sites are removed, the plant has more available energy to spend on the best bud sites. Even so, one should take care not to over prune during the flowering period, for you could shock or stress your rapidly growing plants. And stressed plants can become hermaphrodites.
8. Separate hermaphrodite plants
Cannabis plants are sensitive to stress, especially in the flowering stage of a light deprivation cycle. When plants don’t have a routine light-dep cycle, they experience stress, and this stress can turn female plants into seed bearing hermaphrodites.
The male sex organ of a cannabis plant looks like little bananas. These “bananas” can pollinate nearby female plants if left untended, which can limit the output of an entire harvest.
Separate or quarantine hermaphrodite plants as soon as you see them. You can use these plants to create feminized seeds, which is an economical way of generating offspring that will most likely produce female plants in the future. Marijuana and Hermaphroditism explains in more detail how to avoid hermaphroditism in cannabis.
9. Use clones when possible
Starting with seeds is economical and exciting, but you don’t always know what you’re going to get. Seeds make it difficult to achieve uniformity, because each plant is a different phenotype, and may be male or female.
Clones, however, share the exact same DNA and will produce plants and flowers that are identical in size, smell, and taste. This makes the entire harvest easier to grow and tend, since everything will mature and flower at the same rate.
Clones optimize production and generate a high-quality, uniform product.
10. Buy for quality
It will be tempting to purchase inexpensive greenhouse equipment, but there’s no substitute for quality products that produce quality buds. Don’t risk an entire harvest by purchasing an inexpensive, lower quality greenhouse cover or covering equipment.
Seasoned growers rely on the best-selling greenhouse cover on the market: BOLD®. Conveniently, this product was developed in tandem with the BOLD® EZarm, which gives growers an extra hand while covering and uncovering a greenhouse.
Take advice from the experts.
Learning from the experts is always a good idea. Here are some good places to start:
- Robert Bergman, “How to Prune Marijuana Plants, 7 Tips,” The Weed Blog
- Jorge Cervantes, The Cannabis Encyclopedia: The Definitive Guide to Cultivation & Consumption of Medical Marijuana.
- Michael Cheng (1 July 2016) “Should You be Cloning Cannabis Plants?” MassRoots
- James Defenbaugh, “Canopy Use Tips for Your Cannabis Cultivation,” The Ganjier
- James Defenbaugh, The Light Dep Growers Guide: How to Harvest Marijuana Multiple Times a Year.
- Greg Green, The Cannabis Grow Bible: The Definitive Guide to Growing Marijuana for Recreational and Medical Use (Ultimate Series) 2nd Edition
- Jonathan Katz (4 August 2016) “The Value of Automation,” Cannabis Business Times, July, 2016.
- “Light-Dep/ The Grower’s Best Kept Secret to Increasing Your Harvests,” Americover: Protection from the Ground Up
- Pearl Moon, “What Times Should You Pull Tarp for A Light Dep? 3 Methods,” The Ganjier
- “Proper Ventilation for a Light-Deprivation Greenhouse,” Americover, April 4, 2016
- “Marijuana and Hermaphroditism,” Alchimia Blog: News about marijuana and growing guide
- Ed Rosenthal, David Downs, Marijuana Harvest: How to Maximize Quality and Yield in Your Cannabis Garden