Increasing The Indoor Yield Of Cannabis

Increasing The Indoor Yield Of Cannabis
November 19, 2019

Apart from the joy of cultivating, it is also the rewards later that more than makes up for all the time, effort, and money. Harvesting fragrant and flavorful, and not to mention, potent flowers are a given. Hence, home growers focus on providing the optimal nutrients, equipment, and care to help plants achieve their full potential. Not to mention, also to increase its yield.

In this regard, planting indoors has an inherent advantage. Unlike outdoors, growers have total control over the environment. Achieving optimal conditions also does not equate to spending more. Often, the necessary equipment and tools are in place. All one needs is to understand the factors that affect the size of the yield.

Increasing Yields Indoors

There are several factors that growers pay attention to with regards to optimal harvest.

1. High-Yielding Strains

Some strains are stingy when it comes to the production of buds. Even under the hands of experts, it can only produce so much. Thus, it is in the best interest of home growers to pick varieties taking into consideration its potential yield.

White Widow

White Widow Strain

For decades, White Widow has been one of the most popular strains in the world. In fact, it is also one of the top choices among home growers. Apart from an abundant harvest, it also offers a revitalizing high that is conducive to lively conversations in a social setting.

Flowering Time: 8 to 9 weeks

Estimated Yield: 450 to 500 grams/square meters

Cheese Quake

Cheese Feminized Strain

A slightly Indica leaning hybrid, Cheese Quake ushers in a clear-headed high before leaving users feeling uplifted and relaxed. It may have a subtle hint of grape, but its lineage is evident with the sharp, sour flavors.

Flowering Time: 8 to 9 weeks

Estimated Yield: 350 to 450 grams/square meters

Purple Trainwreck

Purple Star Feminized strain

A hybrid able to induce a profound cerebral high, Purple Trainwreck follows through with a full-bodied relaxation. Although bred to be an Indica-dominant plant, it also has a phenotype that leans on the other side.

Flowering Time: 8 to 9 weeks

Estimated Yield: 500 grams/square meters

Critical Kush

Critical Kush Feminized Strain

Boasting of high THC is not uncommon among modern hybrids. In the case of Critical Kush, apart from its insane potency, it also comes with a better than average CBD. For that reason, it has proven to be among the best recreational/medical combination type of strain.

Flowering Time: 8 to 9 weeks

Estimated Yield: 500 to 500 grams/square meters

Blue Dream

Blueberry Kush Strain

Unlike many Sativa hybrids, Blue Dream does not come rushing into the head. Instead, its stimulating cerebral high have a more gradual progression. And, as it takes effect, the creative juices it squeezes out of the brain takes on a dreamy quality – and does its yield too.

Flowering Time: 9 to 10 weeks

Estimated Yield: 350 to 500 grams/square meters

2. Light Intensity

Growers understand the role light plays in sugar and carbohydrate production to sustain the life of plants. In building the optimal environment, most focus on the type of light and the wattage. However, there is more to it than just the rated power.

As a general rule, plants exposed to higher wattage results in a higher yield. Growers, even beginners, soon learn this while shopping for the ideal grow light system. Apart from the right color spectrum, it is the intensity that has an impact on growth. As such, understanding, measuring and adjusting, can lead to optimal harvest.

Artificial Lighting Systems


In the old days, the measurement of the intensity of light was conveniently based on candles.

A single candle, for instance, casting light on a 12″ x 12″ book at a distance of 12″ would produce one square foot of intensity. Adding a second candle, therefore, increases it by twice, and so on.

Since then, the principle of measuring intensity remains the same. About the only thing that changed was the term used.

1 lumen = 1 foot-candle


The idea behind using lux as a unit of measurement, in theory, was to conform to the metric system. In principle, it is the same as lumen or foot-candle with one fundamental difference. Using the same example given in the previous section, the distance, instead of a foot away, is now a meter away.

1 lux = 1 meter candle

One square meter is 10.764 square feet. Hence, one can say that the intensity of light hitting the book from a single candle is 10.7 lux. Consequently, it can also be stated that the luminosity of light decreased because it has to cover an area of 10.7 square feet as opposed to one.


Reading a book 12″ away from a candle may be enough for some while lacking for others. Adding a secondary candle, then, makes sense as it doubles up the intensity. It is based on this idea that many growers invest in a secondary light source or more.

Proximity, too, plays a role. The principle of Inverse Square Law states that the intensity of light is inversely proportional to the square of the distance. In other words, the farther it is, the lesser the intensity. And, this explains all the fuss about adjusting the height of the lighting fixture in relation to the top of cannabis plants.

Intensity = Light Output / Distance Squared

Consider this:

On average, a typical HPS lamp produces 140 lumens per watt.

400w HPS:  400 x 140 = 56,000 lumens

In essence, cannabis plants receive most of the 56,000 lumens if it is a foot away. However, adjusting it to two feet away results in a significant reduction in the intensity.

Intensity = 56,000 lumens / 2 square foot = 14,000 lumens

From 50,000 to 14,000 lumens, that is already a 75% drop.

Lux Meter

Although growers can estimate light intensity theoretically, it is impossible to determine the level of illumination on different spots, especially towards the edges. One useful tool to help in this task is a lux meter. Although it is sufficient for the needs of most people, it is also not entirely accurate.

Lux Requirements of Cannabis Plants
Life StageMaximumGoodMinimum
Vegetative70,000 lux40,000 lux15,000 lux
Flowering85,000 lux60,000 lux35,000 lux

Lux meters measure light that is visible to the eyes. Unfortunately, it does not take readings of wavelengths that plants need. Furthermore, it works only with HPS, MH, CFL, and T5, but not with LED. Even so, its use lets growers adjust distance and placement of plants for maximum exposure. Not to mention, some people also use the readings to determine the necessity of adding more light sources.

Beyond Light Intensity

In preceding sections, the coverage is mostly centered on light intensity. Granted that many growers use grow light systems, not all are the same with regards to its ability to emit the optimal wavelength needed. In some instances, and most especially when one is budget-conscious, the light source used is not even one designed specifically for plants.

Light, itself, has an extensive color spectrum. Cannabis plants only utilize 400nm (blue) to 700nm (red). It is also referred to as Photosynthetically Active Radiation (PAR) – the only useful wavelengths while others bounce off.

Lux meter can help measure light intensity, but lumens or lux alone does not tell growers if the PAR is sufficient or not. In other words, it is entirely possible for one to provide recommended lux requirements but not achieving maximum yield potential.

A better way to achieve higher indoor cannabis yields, therefore, is to measure PAR. It is determined by Photosynthetic Photon Flux (PPF) – the number of light photons that hit cannabis plants per second.

A PAR meter (PPF meter) takes a reading of the intensity of light that plants could photosynthesize. However, there is one other factor that merits consideration – the quality of the spectrum measured as Photosynthetic Photon Flux Density (PPFD).

Measuring PPF is better than lux and combining it with PPFD raises it to a whole new level.

Typical PPFD Range for Cannabis Plants:

200-400 PPFD: Seedlings, clones, and mother plants.

400-600 PPFD: Vegetative stage.

600-900 PPFD: Flowering or budding stage.

By following these ranges, already, the growth rate of plants increases by 30-55%. During the vegetative stage, growers could adjust lights to induce an explosive growth. For instance, raising 400 PPFD to 800 PPFD further increases the growth rate to 85%.

Typical home growers do not increase the CO2 levels in the grow room. Keeping the PPFD range between 600 to 900, that is not an issue at all. However, once it breaches 1000 PPFD, boosting CO2 becomes a necessity so that the plants could utilize the intense lighting it receives.

If there is one hindrance to many home growers using PPF/PPFD meters, then it is the cost. These instruments range from several hundred to thousands of dollars.

Light Distribution

Cultivating indoors presents a tremendous boost in cannabis yields. Compared to outdoors, plants receive lengthier light exposure. Granted that the right pieces of equipment are in place, growers need to ensure that the surface area of the grow space receives optimal lighting intensity.

Using reflective interiors, hence, is a no-brainer. As an option, too, one could also consider placing extra lights instead of merely increasing the wattage of a lamp.

3. Plant Manipulation

Besides providing optimal environmental conditions and nutrients, growers can train plants. Apart from altering its shape or any of several other reasons, it is also one way of increasing cannabis yields.

Cannabis Trimming

Sea Of Green (SOG)

Often used when space is inadequate, SOG helps maximize the limited area by forcing plants into the flowering stage while still early, usually after two weeks into vegetation. It is suited for Indica because by nature, it is short and stocky with a single cola.

In essence, what growers do is to trim branches beneath dense canopy buds. Doing so lets the plants focus on using its energy on the buds as opposed to the new growths beneath. At the same time, these tiny cuts could also be used to start a new batch.

Because of the quick turnaround time, growers who opt to clone new batches could reap more yield in a season.

Screen Of Green (SCROG)

In a SCROG set up, cannabis plants grow upward and pass through a horizontal screen above. It helps spread the tops evenly and allows for maximum light exposure.


Also referred to as ‘pinching out,’ topping is the process of cutting off the growing tip. Doing so lets it form two kolas instead of only one. Consequently, multiple toppings let growers keep doubling up such as two to four, four to eight.

A single topping encourages plants to grow its lower branches. Multiple toppings, on the other hand, result in upside-down Christmas tree shape plants. Focusing the growth on the top helps increase the yield due to proximity to the light source.


It is mostly the same as topping except for one difference. Instead of cutting a stem between the internodes, growers cut through the vegetative part at the growing tip. And, just like a single topping, Fimming also helps promote lateral branching and new side shoots.

Low-Stress Training (LST)

Unlike topping, LST does not involve cutting. Instead, growers bend and pull the plant down. Doing so exposes the lower branches to the light source. As a result, it promotes the growth of more bud sites. Consequently, it leads to an increased size of yield.

High-Stress Training (HST)

Cannabis plants have a defense mechanism. Under stress, it tends to produce more THC. It may have underestimated humans, though, for it is also the same thing that users desire – or more so its psychoactive properties.

Growers can encourage this behavior by applying HST or more commonly called super cropping. In principle, it is merely a matter of exerting just enough pressure to damage the soft tissues of selected branches. It causes stress which triggers the plant to be bushier. In protecting itself, it grows more bud sites resulting with not only more potent flowers but also a higher yield.


If the lower branches of plants in a tight grow room are not receiving adequate light, the pruning it to develop a lollipop shape growth can help. At the same time, removing foliage at the bottom lets plants pour its energy into the bud sites on top.

Monster Cropping

Unlike the others, monster cropping is different in the sense that it is not directly manipulating plants. Instead, it is taking advantage of SCROG or lollipopping in which the cuttings from a flowering plant could be used as clones.

The thing about cloning a flowering cannabis plant is that it goes back to the vegetative phase. Furthermore, it grows bushier than the mother plant with lots of nodes and branches. Eventually, this results with a much higher yield too.

4. Proper Nutrients

At some point in time during the early stages of growth, growers have to feed the plants. Generally, nitrogen (N), phosphorous (P), and potassium (K) are the three essential nutrients. However, there are also several macro- and micro-nutrients needed too. At any rate, most nutrients have a label that indicates the ratio of N-P-K.

There is no shortage of brands, let alone products, on the market. Typically, these are formulated for two stages of growth.

During the vegetative phase, plants need more nitrogen. It also requires a bit more potassium too. Hence, most general-purpose nutrients for this stage has a ratio of 3-1-2 N-P-K.

Worm Casting As Fertillizer

One thing that growers do need to be aware of is the nutrients already in the medium used. Soil, for instance, already have essential minerals. It is best, therefore, to let plants use it first during the first 3 to 4 weeks before adding. Otherwise, feeding it too early, or too much during the later stages might lead to nutrient burn.

During the flowering phase, cannabis plants need fewer nutrients. Nitrogen may significantly contribute to rapid growth during the vegetative stage. However, it also hinders the ability of plants to produce buds as well as affect its fragrance and flavor. Hence, its level is lowered during this period. On the other hand, cannabis plants receive more phosphorous and potassium.

5. Control The Environment

Light is every bit a part of the environment. In the section on Light Intensity, it is evident that the higher the wattage, the more lumens it delivers. As such, it plays a critical role in the final yield. At the same time, it also generates heat. Consequently, it affects the temperature.

As alluded to earlier, of the many benefits of growing cannabis indoors, one is the ability to control the environment of the grow room.

Cannabis Indoor Controled Environment


Growth rate and yield go hand in hand. One of the factors that could hinder it is temperature. At the optimal range of 24-29°C, plants can photosynthesize efficiently.

Some growers opt to increase the level of carbon dioxide in the grow room. For growers who have a quantum meter, raising the PPFD to at least 1000 allows the plants to utilize the higher intensity of light. In this case, raising the temperature to 30-32°C increases its metabolic rate to achieve an explosive growth fully.

The difference in temperature between day and night time affects the internodal length, and most especially during the first 2 to 3 weeks after triggering the flowering period.

If kept within 4°C, the internodal length is short. As a result, plants can grow denser buds.

Some growers go to the extent of keeping the day and night temperature the same during this time to maximize the internodal growth. In essence, cannabis plants can focus more energy on flower production instead of wasting it on longer stems.

In opting to match the daytime and nighttime temperature, growers should also make sure to do it only within the first three weeks. Beyond, it becomes counterproductive. In fact, it may lead to leaf chlorosis (discoloration).

Finally, consistency also merits attention. A deviation, such as a sudden drop in temperature during the flowering period, can hinder the production of buds. An exemption to this is during the last two weeks. There are particular strains that when exposed to a nighttime temperature of 17-19°C, will stimulate the production of anthocyanin. It can bring out vivid colors (as well as purple hues) making the buds look all the more appealing.


Humidity level can be a hindrance to achieving the full potential of plants with regards to yield. For instance, if too high, it may result in the growth of mildew as well as spread other diseases including root rot. It is for this reason that many growers opt to keep it low. Unfortunately, it could also impact the final harvest.

Plants will always transpire. In other words, it releases moisture into the air as it tries to achieve an equilibrium where the water level inside level out with the surrounding.

As humidity level drops, plants lose more water and could reduce its potential yield. Inversely, a higher humidity level slows down the rate of transpiration.

Clearly, the dilemma presented here is that it is a choice between plants too dry or increasing the risk of diseases. Thus, the only option is to find a middle ground. Transpiration itself is a necessary process for it is how plants could regulate its temperature. Not only that, having the right amount of water allows for the transfer of minerals and nutrients within the plant system. Furthermore, as it lets moisture out through the stomata, it also absorbs carbon dioxide.

  • Cutting/Seedling Stage. Seedlings should focus on growing leaves and its root system. Keeping the humidity at 70-80% RH keeps the rate of transpiration on the low side, but there is not much imbalance during this early stage.
  • Vegetative Stage: As the plants vigorously grow and prepare for reproduction, keeping the RH to 50-80% is ideal. It takes into consideration that as it becomes bigger, it has more surface area to transpire.
  • Flowering Stage. During this time, high humidity level could result in the dreaded root rot. Growers could now lower it to 40-50% RH.

Air Circulation And Exhaust

One of the limiting factors of cultivating cannabis in a grow room is access to fresh air. In the outdoors, that is not a concern unless there is a change for the worse in the weather. Not when indoors though as growers have complete control. Having proper air circulation is essential to health, and consequently, the quality of buds and yield.

During transpiration, air movement lets plants release more moisture. In turn, it draws in water from the growing medium. And, in doing so, it also absorbs essential nutrients and minerals. The constant removal of moisture also results in the decreased likelihood of mold, bud rot or white powdery mildew.

As presented in earlier sections, temperature and humidity play a critical role. Hence, controlling air circulation is the key to providing an optimal climate inside a grow room for plants to achieve its full potential.

In a basic grow room, there are three kinds of fans that growers need.

  • Exhaust Fan. Stale air needs to be let out and so does heat. A typical grow room will have a fan the vents out air. As an option, growers could also attach a carbon filter to eliminate odor too.
  • Intake Fan. Air exchange should occur every 1 to 2 minutes. As stale air is vented out, fresh air comes in to help maintain proper temperature and humidity levels.
  • Additional Fans. Depending on the size of the grow room, growers could use an oscillating fan to cast a slight breeze. If space is tight, small clip-on fans could also be used. Not only does it help with air movement with regards to maintaining proper humidity, but it causes the stems and leaves to sway. As a result, plants could become stronger.

6. Container Types And Sizes

The root system of cannabis plants come to mind when it comes to the type of container and sizes. In essence, growers want to make it most conducive to healthy development. Some of the factors that come to play are moisture, oxygen, nutrients, and pH.

Cannabis On A Bucket Containers
  • Regular Pots. Usually cheaper and readily available, regular pots have been in use for a long time. Having a saucer at the bottom also helps catch runoff water.
  • Smart Pots. Also called Fabric Containers, these pots provide more oxygen to plants. Since water dries from the sides, there is less risk of overwatering. However, growers will also need to water more often. To offset, some people opt to use twice the size of regular pots. Another key benefit is that through the process of air pruning, it helps plants avoid root-bound.
  • Air Pots. It has the same benefits as smart pots. Air pots, though, are tall and thin. As such, it may be better suited for come plants that tend to grow tall as opposed to bushy. Furthermore, some growers may find it a better alternative in small grow rooms.
  • Hempy Buckets. Ideal for large cannabis plants that need plenty of water. It is practically the same as regular pots except that the drain holes are on the side instead of the bottom. By holding a small pool of water at the bottom, there is less need to keep watering. However, the nutrient buildup and stale water could also be problematic.
  • Hydro. It is not a type of container, but a soilless growing method. Many growers prefer this system of feeding the plants directly for rapid growth. Some strains, though, have a better profile when grown in soil. Other than that, hydro is perhaps the best way to go in achieving the highest indoor yield possible.

Some people go by the general rule of using up to 2 gallons per foot tall. It could be a good start in determining the size, but it is also not reliable. For example, many cannabis strains are short but incredible bushy. And, if the pot is too small, then the root system will run out of space.

For many home growers, the most common size used is 3-gallon pots. It is a good compromise on size between what plants need and a typical grow room. If possible, space-permitting, then 5-gallon pots are excellent for practically any strain as it affords all the space necessary for an extensive root system.

7. Use Trellis

Most cannabis growers would only support stems if growing strains that produce massive and weighty buds. In fact, the thought of using trellis has not crossed the minds of most too.

Trellis often involves the use of latticework or crosses and could be made from different materials. Its only purpose is to provide stability and support as plants approach maturity.

Cannabis Attached To A Trellis
  • Vertical Trellising. Often made of wood, metal or bamboo with horizontal interconnecting pieces. Typically installed early on individual plant sites.
  • Horizontal Trellising. Can be used in small areas but most suitable for large commercial-size growing spaces. Often, these are nettings or screens with wide holes hanged over the canopy and supported by any vertical structure. These trellises should be installed no later than the vegetative stage to give plants sufficient time to grow through.

By employing smart pruning techniques on its branches, growers could increase the average yield by 25-35%.

Harvesting High Yields Of Cannabis

From the strain to its growing conditions, numerous factors affect the production of buds. Even if some plants are what is deemed as beginner-friendly, there is work to be done. Not to mention, the cost of having the right equipment, tools, and nutrients.

Granted, beginners in growing cannabis may have complicated or confusing moments throughout the journey, it gets better during the succeeding batches.

At any rate, once harvest time comes, one thing that growers should keep in mind is to resist the temptation to do so. Consider too, that no matter the advertised flowering time of strains, not all plants grow precisely the same. In other words, some may require more time.

Cannabis Leaves

After spending time and effort, the last thing one wants is to harvest too soon. In some cases, growers could lose a quarter of the potential yield. And, worse, compromise the quality of the buds.

Increasing the yield of cannabis indoors is not merely a matter of knowledge or skill. It is also a habit. Some people have the patience while others do not, for instance. Keep in mind, though, that the amount of buds harvested in one batch is great. But across multiple batches, it is insane.