How to achieve a maximum indoor cannabis harvest? This is the question that many people ask themselves after a successful first harvest.
Increasing your yield is relatively simple if you follow the advice we give you in this guide. You will only be limited by your budget and the time and space you have available for indoor cultivation.
The techniques and knowledge required are not very complicated and we tell you absolutely everything in this article.
Only a few advanced techniques such as SCROG or CO2 supply require a little more knowledge.
However, be careful not to fall into the trap of extreme optimization.
Some beginners waste a lot of money and time on advanced optimizations that do not pay much.
And because they are preoccupied with these complicated optimizations, they forget the basics of indoor cultivation. This can lead to ruined harvests.
In this article, we focus on the most effective optimizations to generate a maximum harvest.
Pareto’s law: 80% of the results come from 20% of the effort.
You could embark on a hundred different optimizations. But here we give you the 20 optimizations that will give you 80% of the productivity gains for your next indoor session!
To make it easier for you, we have divided these methods into 5 sections :
- Improve your Lighting
- Optimize your Culture Space
- Maintain Air Quality
- Use Advanced Cultivation Techniques
- Additional Tips (But Not Optional!)
Once you have learned and applied these tips, all you need to do is be patient until the end of your session to achieve a record harvest.
Read this guide through to the end. The very last section gives you a list of high-yielding cannabis strains!
Upgrade your Lighting for Maximum Harvest
Lighting is of course the most important element when you want to increase your harvest. The amount of light and the quality of your lighting will largely determine how much weed you will harvest.
If you were to retain only one thing from this guide, it would be that you don’t want to save money on the purchase of your horticultural lighting.
1. Choose the Right Type of Lighting: Recommended MH and HPS
Many beginning growers believe that cannabis plants just need light to grow properly.
In reality, if you want to make a big crop, your plants will need a lot of light. And even if you want to generate a lot of light, you want to make sure you use the right type of lighting for your plants.
It would be a shame to spend so much electricity if your plants are not able to turn this light into big, compact buds.
The best lighting for indoor cannabis cultivation is discharge lamps. There are 2 types of bulbs: Metal Halide (MH) and High Pressure Sodium (HPS).
Because of their light spectrum, MH bulbs are better suited to the growth phase of cannabis. Whereas HPS bulbs are intended for the flowering phase.
Both MH and HPS lamps are very efficient in terms of yield because their spectrum is largely absorbed by the plants, which allows a large part of the energy consumed to be converted into light that can be used directly by the plants.
Other types of lamps such as CFLs do not offer the same efficiency above a certain power level.
MH and HPS lamps are particularly suitable for high-powered lighting. There are bulbs from 150 watts to 1000 watts.
Is there an alternative to HPS lamps?
A good alternative to MH and HPS lamps? LED lamps. However, these are still very expensive, at least if you opt for quality material. Count more than 1000 euros for the LED equivalent of a 600 watt HPS.
Moreover, even though LEDs are improving very quickly, they are not yet up to the HPS for the flowering phase.
The advantage of LEDs is their low power consumption compared to HPS. Indeed, you can replace a 600 watt HPS lamp with an LED panel of only 400 watt. This makes a big saving in electricity in the long run.
But it will take quite a few sessions to amortize your purchase.
2. Increase the Power of your Lighting
This is the most important point in this whole guide to increasing your cannabis harvest: just increase the power of your lighting!
So be careful, there are of course other parameters to take into account, such as the size of your growing space (read below) or the power of your ventilation system (also below).
But the truth is that if you want to harvest more weed, you have to give your plants more light!
To give you an idea of the importance of lighting power, here is an estimate of the harvest based on two lighting powers, all other parameters being equivalent:
The ideal wattage for an HPS lamp is 600 watts. This is the most efficient voltage in terms of the energy returned to the plants in the form of light.
Above 600 watts per lamp, the efficiency per watt decreases. That is why we recommend multiplying the lamps instead of investing in a 1000 watt lamp.
For example, you will harvest more weed with 5 HPS 600 watt lamps than with 3 HPS 1000 watt lamps. Even though in both cases you will consume the same amount of energy: 3000 watts.
To conclude, if you are currently in 250 or 400 watts, switch to one 600 watt lamp. If you are already in 600 watts, consider adding a second 600-watt lamp, instead of switching to a single 1000-watt lamp.
3. Improve the Quality of your Lighting: Ballast, Bulb and Reflector
After choosing the right type and power of lighting, you can still gain a lot by improving the quality of your equipment.
This is because the ballast, bulb and reflector you use play a key role in the amount of light you give back to your plants. And that, in turn, affects the maximum harvest you can achieve.
We wrote an entire article on choosing the best ballast. But to put it simply, you have to choose a quality electronic ballast.
There are 2 types of ballasts: magnetic and electronic.
Electronic ballasts generate much less heat than magnetic models and give much more light back to the plants.
Lumatek Dimmable Ballast
For MH or HPS lighting, an electronic ballast will give between 30% and 50% more light to your plants.
This type of ballast therefore allows you to optimise the use of the energy consumed. And therefore to increase your harvest significantly.
The best ballasts are those of the Gavita brand. They are quite expensive but the investment is worth it.
If your budget is limited, choose an electronic ballast from Lumatek or Nanolux.
The choice of bulb also allows you to pick up a few grams more on your next harvest.
Choose a bulb suitable for electronic ballasts and if possible, the same brand as your ballast.
Here again, Gavita remains the best option if you have a ballast of the same brand.
The Lamp Reflector
We have also written a comprehensive guide to choosing the best reflector.
The reflector allows a maximum amount of light to be reflected back to the plants. Beginners often opt for a basic stucco model, but open reflector models offer a much higher level of reflection.
In addition, open reflectors prevent the creation of hot spots by distributing the light more evenly.
Finally, open models have the advantage of allowing the lamp to cover a larger area of crop.
For example, with a 600 watt lamp and a basic reflector you cover about 1.5m². Whereas the same lamp with an open reflector can be sufficient for a space of 2.25m². That is 50% more growing space!
In terms of brands, the best known is Adjust-A-Wings.
But you can also opt for a model from Prima Klima, which is much cheaper and just as efficient.
4. Optimize the Exposure of Plants to Light
Now that you’ve done the biggest thing in terms of improving your lighting, we can move on to more subtle optimizations that will allow you to add a few grams of weed to your precious crop.
The exposure of your plants to light should be as even as possible. This ensures that your plants grow uniformly and prevents certain plants from taking up all the space in the growing area.
A canopy of uniform size and density will give a more generous harvest than a wild garden where plants try to shade themselves to steal the little space and light available.
There are two ways to optimize the plants’ exposure to light: either by moving the lamp or by moving the plants.
Makes sense, doesn’t it?
To move the lamp, you can use an electronic rail that makes the lamp go back and forth permanently during daylight hours.
We also advise you to rotate the plants when watering or once a week. Take the most off-centre plants and place them in the middle of the growing space, and vice versa.
If some plants are too small to receive light from the lamps, you can raise them by placing them on a stool or on an upside down pot.
5. Respect the Distance between the Plants and the Lamp.
This may seem obvious to experienced growers. But all too often I see beginners investing in high-end equipment, with very advanced technical optimizations, while the distance between the plants and the lamp is not adjusted.
And the consequences can be catastrophic.
20 cm too low, your lamp will burn the tops of your plants in just a few days. It would be a shame to burn the big buds on top!
20 cm too high, and your plants will start to tiggle enormously. This means that they will grow very quickly in height in order to get the light they need, instead of developing their secondary branches. The result: very thin plants and crop compared to small, thick bushes.
For a 600 watt HPS lamp, keep a distance of 50 to 60 cm between the tops of your plants and the bulb.
Distance between Lamp and Maximum Harvest Cannabis Plants
The best technique to maintain the right distance at all times?
Attach a string to your reflector with a length of 50 to 60 cm (for a 600 watt HPS or MH) make sure that the end of the string always reaches the top of your plants.
No higher, no lower!
That way you can’t go wrong.
Reinstall your lamp as soon as the tops of the plants are higher than the end of the string.
6. Add Secondary Lighting
Finally, if you have performed all of the above lighting optimizations and want to go further, you can opt for secondary lighting.
This involves placing one or more additional lights, usually weaker than the main lamp, at the bottom and/or sides of your growing area.
This allows the branches at the bottom of the canopy to receive more direct light and thus grow faster. With side lighting, you give off-centre plants a little more light to even out their exposure.
The effectiveness of such a device is limited by the power of the additional lighting.
Indeed, it is not possible to place a 600 watt HPS lamp at the bottom of your growing space because it would burn your plants.
Most growers who choose secondary lighting opt for an LED or CFL (compact fluorescent) lamp.
Their low power consumption and low heat emission make them a good option for such a device.
Be careful however not to fall into extreme optimization, it is not a question of decorating a Christmas tree with electric garlands!
Stay on horticultural lighting and on reasonable wattages.
Optimize your Growing Space for Maximum Harvest
Now that your lighting is at its best, you need to make sure that your growing space allows you to achieve your harvest goals.
7. Increase the Size of your Growing Space
As you probably know, increasing the size of your growing space is the first thing to do if you want to harvest more weed.
Just like lighting power, the size of the growing area has a direct impact on the amount of weed harvested.
Indoor Cannabis Growing Space Secret Garden
For example, by doubling your growing area, you can double the power of your lighting and therefore double your harvest.
Indeed, if you manage to harvest 400 grams of weed with one 600-watt lamp in 1.5m², you will manage to harvest 800 grams of weed with 2 600-watt lamps in a space of 3m².
If space and power consumption are not a problem for you, don’t hesitate and increase the size of your growing area.
8. Cover the walls with Mylar or White Matte Paint.
For growers who own a grow tent, this is not helpful. Commercially available boxes are already covered with Mylar or white canvas.
However, if you have built your closet yourself or if you are reusing an existing space, the walls may not reflect light well.
In this case, you should cover the walls of your grow room with a reflective material.
These materials allow you to reflect as much light back to your plants as possible instead of wasting it on the walls.
The most effective:
- The white tarpaulin
- Matte white paint
- A lot of beginners are busting their brains about what to choose between Mylar, white tarpaulin and matt white paint.
There are even different finishes for Mylar: brushed, hammered, Diamond, Gold, etc.
In reality, it doesn’t make much difference.
The important thing is that your walls are covered with one of these materials. So you don’t need to spend more money on “Super Diamond Mylar” if you have a can of matte white paint on hand.
Save that money to buy better seeds!
9.Raise the pots 10 cm above the ground.
This is a small optimization that is totally free and requires almost no effort!
Take care to raise the pots at least 10 cm above the ground.
This creates a layer of air between the pots and the ground and thus protects the roots of your plants from cold weather.
The soil cools down if the pot is in contact with cold soil. This can slow down the growth of your plants, especially in the early stages of growth.
To avoid this, elevate your plants by placing them on an upside down pot or something else (whatever you have on hand!).
Some people use polystyrene sheets like the ones used for household appliance packaging.
Others prefer to place a wooden pallet on the floor of their grow closet.
It’s up to you to see what you find, so be creative!
Maintain Air Quality
The quality of the air in your growing area is one of the most important factors in indoor growing.
Indeed, the air your plants breathe plays an essential role in their development.
The temperature, humidity and composition of the air affect the health of your plants.
10.Use an Adapted Ventilation System for Optimal Conditions.
To guarantee the good development of your plants at all stages of the session, you must make sure you have a ventilation system adapted to your installation.
The climate management system for a 400 or 600 watt installation always includes:
- An air extractor to expel hot and stale air from the growing area
- A duct fan for interaction (insufficient passive interaction), allowing fresh air to enter the culture space.
- An air blower to simulate the action of the wind.
- A weather station to monitor temperature and humidity levels
- We recommend that you invest the right amount in the air extractor.
Prima klima models offer an excellent price-performance ratio.
What Extractor Power?
For a 600 watt installation, you will need an extractor with a power of at least 400m³/hour to limit the problems of extreme heat.
However, opt for an 800m³/hour model if you want to have peace of mind. The price difference is minimal and you will not regret the investment!
For interaction, take a duct fan of 180m³/hour if your extractor is 400m³/hour. Or 300m³/hour if you have chosen an air extractor with 800m³/hour.
For the air extractor, you can opt for a large fan placed at the top of the growing area. Or several small clamp fans that you can position closer to the plants.
In any case, make sure that all your plants oscillate slightly.
Finally, place a weather station in your grow room to make sure that the temperature and humidity are always appropriate.
11. Invest in an Air Humidifier to Maintain the Right Humidity Level
At the beginning of the growing phase, cannabis plants need a very high moisture content.
This can be complicated, especially if the ambient air in your area tends to be dry.
And the bigger your closet, the harder it is to increase the humidity level with grandmother’s methods.
So you’re going to need a humidifier.
Indoor Cannabis Growing Air Humidifier
There are different types of humidifiers. We advise you to avoid the cheaper models as they will not last long.
One of the main disadvantages of humidifiers is that their water tank is quite limited. Therefore, they need to be refilled regularly.
Tip: Connect your humidifier to a timer so that it operates intermittently. This will extend its autonomy.
Use Advanced Cultivation Methods for Maximum Harvest
In this section, we present you with 3 optimizations that are quite advanced but that are really worth it when done successfully:
- Cultivation in SCROG
- CO2 input
12. Culture in SCROG
SCROG or Screen Of Green is a cultivation method that aims to optimize the use of the cultivation surface. It consists of placing a net or screen over your plants and braiding the plants along the mesh of the net in order to cover the entire growing surface with large buds during flowering.
This makes it possible to achieve a large harvest with a limited number of plants in a limited space.
It is possible to make a SCROG with only one huge plant. But this will require a very long growing phase.
We therefore advise you to grow several plants to be able to harvest faster.
Indeed, 5 plants will be able to cover the grid much faster than one plant.
Growers who have mastered SCROG often achieve record harvests in terms of grams per square metre.
Hydroponics is an advanced indoor growing technique that consists of irrigating your plants continuously and automatically, in order to optimise their nutrition and therefore their speed of development.
Most often, hydroponics is done with an inert substrate such as clay balls or coconut fibre instead of potting soil.
The potting soil acts as a buffer because the nutrients must first dissolve in the soil before being absorbed by the plants.
With an inert substrate, the nutrients are absorbed more quickly by the plants.
Hydroponic Growing System for Indoor Cannabis Cultivation
Hydroponics allows plants to grow faster. This allows you to go into bloom sooner, but also to have huge buds at harvest!
Be careful though, if the water in your hydro system is not good, or if there are too many or too few nutrients in the water, you will pay for it immediately.
Although automatic, a hydroponic system requires regular attendance to ensure that the irrigation water is of good quality.
14. The Contribution in CO2
The CO2 input is the most advanced optimization in this guide.
But it is also one of the most efficient, when well done.
You might as well tell yourself right away that the CO2 management system is expensive and that you need to do some calculations before you know exactly how much CO2 to supply to your plants.
But once the investment, calculations and adjustments are behind you, you can achieve a harvest that is up to 30% bigger.
CO2 Bottle with Manometer for Indoor Cannabis Cultivation
In order to achieve a regular CO2 supply you will need the following:
- A CO2 cylinder
- A solenoid valve
- A pressure gauge
- A CO2 management system (if you want the supply to be automatic and accurate)
- A few meters of plastic tubes to distribute the CO2 in the growing area.
The 2 Methods of CO2 Supply
There are two main methods of making a CO2 contribution. But we won’t go into details in this article.
The first method is to use a solenoid valve to regulate a continuous supply of CO2. This involves calculating the necessary supply to your plants by considering the extraction power.
The disadvantage is that you spend a lot of CO2 for nothing and you have no idea how much CO2 is in the growing area. The only thing you do know is how much you are injecting.
The other method is the regulated method. You have to use a CO2 regulation system to do that. It’s a device that continuously measures the composition of the air and its CO2 content.
The system injects CO2 only when necessary. In addition, there is no risk of injecting too much, because the supply stops as soon as the air contains enough CO2.
Additional Tips (But Not Optional!)
Finally, here are 6 additional tips to achieve maximum indoor harvesting.
Attention, additional does not mean optional!
15. Water your plants neither too much nor too little.
It may seem obvious, but many beginning canola growers make watering mistakes that cost them a lot of money.
Underwatering can result in stunted growth, limited bud development and even plant death if the lack of water lasts too long.
Watering Cannabis Plants
On the contrary, over-watering can lead to the development of mould on the roots, stunted growth and in some cases the development of fungi that can kill the plant.
To know when to water, simply press your finger 2 cm into the soil. If it is dry, you must water. If it is still wet, you can wait until the next day.
Easy, isn’t it?
16. Cut off the Branches and the Lower Heads that do not receive light.
Again, this is a completely free optimization that will have a significant impact on the amount of weed you will harvest.
Indeed, the plant will spend a lot of energy to develop a multitude of very small buds on the lower branches.
This energy is much better used if it is concentrated in the large top heads.
The result: a more generous harvest and bigger, more compact buds.
In addition, it will be easier to water and care for your plants if the lower canopy is clear.
Finally, it will save you a lot of time during the harvest.
There’s nothing worse than manicuring tiny heads.
On the other hand, if you only have a few big buds to manicure, it will go very quickly!
17. Use the right Fertilizers and Respect the Dosages
Fertilizers are a must for indoor cultivation. We have published a complete guide of the best fertilizers for cannabis cultivation.
Indeed, even if you use a nutrient-enriched potting soil, your plants won’t stay healthy for 3 months without any additional input.
And in this guide, we talk about optimizing our production in order to achieve a maximum harvest.
Fertilizer and supplements increase the quantity and quality of the harvested weed.
For a maximum harvest, we recommend the following fertilizers and supplements:
- Root stimulator to strengthen and accelerate root development.
- Growth nutrient solution – basic fertilizer for the growth phase
- Flowering nutrient solution – basic fertilizer for the flowering phase
- PK booster at the end of flowering to provide the plants with the potassium and phosphorus they need at this stage.
- Flowering stimulator to facilitate the plant’s assimilation of nutrients and thus encourage the production of larger buds.
- Don’t let us be seduced by the promises of fertilizer sellers. The 5 products above are all you need. Most of the other supplements will have almost no effect on the harvest.
Remember the 80/20 rule.
The only supplement you can add is a flavour enhancer.
I would strongly advise against it because most of these additives alter the original taste of the variety.
So if you have 3 different varieties grown with the same flavor enhancer, you will notice that all three will have a certain taste in common: that of the enhancer.
Respect the Doses
It cannot be repeated often enough: respect the fertilizer doses indicated by the manufacturer.
This is the best way to avoid over- or underdosing your fertilizers and supplements!
18. Flower at the Right Time
The time of flowering is crucial for your harvest.
More than just an optimisation, it is a necessary condition if you want to make full use of your growing space and the power of your lighting.
The key element is that the plants must occupy the entire growing space in the middle of flowering in order to maximise the use of space.
Indeed, if you go into flowering too early, your plants will not occupy all the growing area at the end of flowering. This means that you will have wasted space and lighting power.
On the contrary, if you start flowering too late, your plants will have grown too much and will not have enough space.
They will fight for light by growing vertically which will quickly become unmanageable.
In addition, the lack of space will drain the plants’ energy instead of concentrating this energy on the production of large resinous buds.
If you grow SCROG as we advise, this step is even more important.
Indeed, the purpose of SCROG is the optimization of the growing area.
It would be a shame to complicate your life with a SCROG for a modest harvest.
How do you know when it is the right time to go into flowering?
There is an easy way to know when it is the right time to pass your lights in 12/12 hours and start flowering.
Just wait until your plants cover 70-80% of the growing area.
19. Don’t Harvest Too Early
Just as it is important to float at the right time, it is also important to harvest at the right time.
Many beginners tend to want to harvest too early.
If you harvest too early, not only will you end up with a weed that’s not ready and lacks taste and effect, but you’ll have a smaller crop.
In fact, buds continue to grow until the last day of the session.
I even advise to leave the plants in their pot 48 hours after turning off the lights, before finally cutting them to dry.
To know when it’s time to harvest, you have to observe the trichomes on the buds.
You can do this using a small backlit microscope, sold in growshops. Or by taking a picture in macro mode. You can then simply zoom in on the photo to observe the trichomes.
The trichomes are transparent at first, during most of the flowering phase.
At the end of flowering, they become milky, then some take on an amber colour.
It is time to harvest when the trichomes are between 25% and 50% amber.
If you wait until all trichomes are amber, your weed will have a very stoned (sleepy) effect.
On the other hand, if you harvest when the trichomes are 75% milky and 25% amber, your weed will have a higher (euphoric) effects.
So choose according to your preferences, but be sure to wait for the right time to harvest.
20. Choose High Yield Varieties
Finally, the choice of varieties you grow will also have a strong impact on the amount of weed you will harvest.
Generally speaking, Sativa varieties have lower yields than Indica varieties.
Sativas also flower longer than Indica strains. Indoors, this means fewer sessions per year and a higher electricity bill per session.
And even within the two large Sativa and Indica families, some cannabis strains have genetics that tend to produce higher yields than others.
Don’t overlook the quality of the seeds or cuttings you’re going to grow.
Make sure they come from a quality breeder and have been stored properly.
Dinafem Cannabis Seeds
We have prepared a list of the highest yielding cannabis seeds available on the market.
Feel free to suggest other high-yielding strains in the comments!
- Critical 2.0 – Dinafem
- Big Bud – Sensi Seeds
- Monster – Eva Seeds
- Northern Light – Sensi Seeds
- Industrial Plant – Dinafem
- Money Maker – Strain Hunters
- Big Foot – Sweet Seeds
- Super Critical – Green House Seeds
- Power Plant – Dutch Passion
- Super Skunk – Sensi Seeds
- Moby Dick – Dinafem
- Big Bomb – Bomb Seeds
- The Ultimate – Dutch Passion
There are thousands of varieties of cannabis, so the list is not exhaustive.
Look for the most productive strains in the catalogues of your favourite breeders.
Most seed banks have at least one variety specially developed for high yield.
Did you just read the whole thing in one sitting?
Now you know how to achieve maximum yield in your next indoor session.
Lighting, growing area and equipment are of course crucial to the yield of your crop.
But don’t neglect the productivity gains from advanced growing techniques such as SCROG and hydroponics.
Finally, follow our additional tips to the letter if you want to have a chance of reaching your maximum harvest.
And remember, the important thing when doing optimization is to focus on what is most important, what is strictly necessary.
Once you’ve mastered the basic optimizations, you can add a little more advanced optimizations.
For more harvest estimates, read our article: How many Grams per Plant.
Do you have too limited a budget for all these optimizations? Find out how to grow cannabis as cheaply as possible.
And finally discover our complete guide to Harvesting 500g of Indoor Weed.