Essential tips to start growing indoor cannabis

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Illustration representing a grower in a house doubting how to start growing marijuana
Illustration representing a grower in a house doubting how to start growing marijuana


We are in the best season for indoor crops and from your favourite growshop we want to share our experience, hoping you achieve the best results with your indoor crops yield and, in the process, avoid losing because you made a key error in the process.

Based on certain common questions asked by our clients and readers, I’ll share with you some tips to improve your crops. Remember, growing indoor cannabis is a form of art, and as such, it needs certain knowledge if you want to increase your crop yield.


Probably you have heard before about the gram/watt rule, in all honesty, you should ignore it. Even if it works as a reference to find out how are you doing so far, this is only applicable if you are using the light of sodium lamps, return of a LED (up to 1.4 grams/w) or a LEC (up to 1.7 grams/w) is quite different, and all this without taking into account the genetics you’ve chosen.


Even if your favorite seeds are feminised or autoflowering, I’m pretty sure you’ll want the best results for your crop yield, THC levels and terpenes, if you get marijuana seeds from PEV Seeds you’ll be starting on the right path.


So let’s move forward, I’ll try to summarize the most important aspects to keep in mind if you want a successful crop.


Setting up a quality indoor crop, a very important advantage of cultivating indoors is the fact that we can control all the elements a marihuana plant needs to grow in the most optimum way. Outdoor weather and air flow change constantly, but indoors, we can control all these things such as temperature, humidity, CO2 levels and lumens per square meter.



Growing Cabinet



Grow Tent growing cabinet
Armario de cultivo Grow Tent


The Grow Tent Indoor Grow Cabinet. Made entirely of top quality aluminum and lined with a reflective interior that makes the lumens emitted by the focus are fully exploited by your plant…


Available in different sizes, so that, based on your growing space, you can choose the one that best suits your needs

– 80x80x160 cm.
– 100X100X180 cm.
– 120X120X200 cm.

More information about
Grow Tent growing cabinet



Even after seeing marihuana grow in many types of indoor spaces, we always recommend professional crop cabinets, which are completely sealed to outside light and atmosphere, only connected to the exterior by ducts adapted for air flow, meaning, intraction and extraction. In addition, it isn’t recommended leaving a single free space for cultivation due to odor dispersion, which we do not want to be detected outside our growing cabinet.


It’s important to choose a cabinet that has all the quality points we propose, one that gives you full control of weather, illumination and odor emissions.


For example, in a 100 x 100 cm space you’ll be able to have a 4 to 42 plant indoor crop, but the size of your cabinet depends on your budget and commitment.





Let’s talk about pots you need to grow your marijuana indoors, there’s an infallible rule “100 liters of substrate/m2”. With this in mind, you’ll be able to customize the size of your pots, depending on the growth time you prefer, if you want a shorter cycle, then, choose smaller pots, and apply a shorter growth time to the plants, but if you are not in a hurry, you can choose bigger pots and wait a few more weeks before moving them to flowering.


I always use 9 pots of 11 liters per square meter and it usually takes around 3 months from germination to harvest.



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Air Extraction


WK metal Dospel Extractors
WK metal Dospel Extractors


The most elegant and effective set of extractors, WK METAL, from Dospel. It has much more power than other competitors of the same size.…

WK-100 metal Extractor
WK-125 metal Extractor
WK-150 metal Extractor
WK-200 metal Extractor
WK-250 metal Extractor
WK-315 metal Extractor

More information about
WK metal Dospel Extractors




Lamps generate high amounts of heat, and the temperature of your indoor closet could rise up to 28 ºC, which is the critical temperature that we should never exceed.


The extraction systems, with soundproofing elements, should stabilize your crop temperature, likewise, due to them being soundproof, they’ll cushion most of the sound coming from the extractor.


The extractor must always be connected with the lamp on. During the darkness phase, it’s recommended to connect it 15 minutes each hour, and during the last weeks of the flowering period increase it to 15 minutes every half an hour.


If you live in a zone with a very humid climate and its relative humidity is higher than 80%, it would be a good idea to always have it working.


With a hygrometer you can measure humidity in the atmosphere, it shouldn’t exceed 75% nor go below 20%.


The ideal hygrometry should be between 40 and 60%. But there should be no problem if occasionally there is a relative humidity of 90%. The thermohygrometer is essential to control the climate of our crop.



Air Conditioning


If you have an indoor crop in the middle of winter or summer, it would probably be a good idea to control the air temperature by installing an air conditioner system, with these devices you’ll be able to get a clean and dry air flow, free of impurities, and this is essential during the flowering period of your plants.


If you live in a zone with a relatively high humidity (coastal zones for example), maybe installing an air dehumidifier will be more than enough.


Remember that the temperature can’t be higher than 30ºC and never below 15ºC. The adequate climate should oscillate between 20 and 28º C.



Lighting for Indoor Crops



Electronic LEC Philips 315 Illumination Kit
Electronic LEC Philips 315 Illumination Kit


This technology is more efficient than traditional luminaires. In case of HPS or MH lamps, the efficiency is 40% lower in watt-lumen ratio. That’s why this kit is equivalent to the 600w lighting kits with sodium lamps and metal halide lamps….

Power: 315W
Input tension: 210-250V
Power Factor: >0.95
Frequency: 50-60Hz
40cm x 28cm x 22cm
Weight: 6kg

More information about
Electronic LEC Philips 315 Illumination Kit




The best illumination technology that we currently have can be acquired with LEC luminaries, Light Emitting Ceramic, these are high performance and low heat diffusion systems, with high measured results in the production of grams of cannabis per watt consumed.


Without a doubt the best for your indoor crop!


On the other hand, if you are a traditional cultivator, the HPS luminaires (High sodium pressure) are the best options regarding crop yield, although life cycle of the product is way shorter than LEC, and it also has the disadvantage of overheating the atmosphere of your crop.


The high pressure sodium bulbs are suitable for the vegetative and flowering phase, being able to find specifics for each phase, or maybe mixed ones to use during the whole cycle of your crop.


The most common lamps are 250, 400, 600 and 1000 watts. Lasting for at least 3 crops, after this time, they will stop working.


Both HPS and HM bulbs require a ballast, the most durable and efficient are the electronic ones with a power regulator. But there are some more economic options, such as the ones with magnetic reactances.


How to use Lamps Indoors?


The reflector must be placed half a meter from the plants (with sodium 600 watts lamps) or 35/40 cm of illumination (with sodium 400 watts lamps), keeping this distance during the growth period. During the vegetative phase marihuana plants need 18 hours of light and 6 hours of darkness. This period goes from 1 week to 5 weeks, and this will depend mainly on the size of the pot you choose.


On the other hand, during the flowering time, the plants need 12 hours of light and 12 hours of darkness (it’s very important that it is in total darkness). The duration of the flowering period can vary and change from 50-70 days, depending on variety.


This table is used as a reference for the nominal power in recommended HPS or HM lamps, depending on the available space.


Optimum crop space:

0.5 square meter………. 250 W.
1 square meter…………. 400 W.
1.5-2 square meter……. 600 W.
3 square meter……….. 1000 W.


Another option available in the market is the CFL or fluorescent bulbs. They are used in small crops or in the maintenance of mother plants. They do not emit heat and there are many options available from 105, 150, 200 and 250 watts.


In 2018, LED technology was the main one, when talking about indoor marihuana crop with the best warranties. More and more efficient and with better performance, especially in the flowering phase.


The Led panels  have a 50.000 hours life cycle and you will also save around 60% in your next energy bill.


I recommend checking our catalog if you want to know more about this luminary.



Odor Treatment


As we shared with you, to avoid any issues, install some kind of odor treatment system, so no one will ever smell your indoor crop.


To do so, you have the option to incorporate an activated coal filter in the extraction tube, it will absorb all the odor molecules. Its main disadvantage is that the filter eventually gets saturated and you will need to change the activated coal for each crop.


Another option is ozonizers, which release ozone as it passes through the extraction air, destroying any molecule of smell, smoke, or microorganism




Is the reflector important for my indoor crop?


The reflector is essential to grow marihuana, it improves a lot our crop yield. The reflector reflects upwards the light from the bulb, focusing it on the plants.


The most common ones are:


Open reflectors, these are the cheapest, compared to others, but they cause a big loss of lumens.


Powerful Closed reflectors, more efficient than the open ones, some have a thermal screen to diffuse heat from the bulb and redistribute it to the plants. There are also some reflectors with an electronic ballast included.


Cooltube Glass reflector + adjustable wings (extra aluminum)


With Cooltube devices you get the advantage that the injected air goes directly to cool the bulb, taking advantage of the heat generated by it to stabilize the cabinet temperature if you are growing cannabis during winter. Also, it improves the efficiency and durability of HPS bulbs.


As you can see, you have many options to choose from, but if you want my advice, the Cooltube reflector is the best one considering quality/price.





How to water the cannabis plants of our indoor crop?


Marihuana plants need more irrigation after the first three to four weeks, around 180 ml per plant each day. At the beginning of the flowering period we will increase the watering to 250 ml and during the last two weeks, before the harvesting period, we will reduce it to 150 ml per plant each day.


This is only one reference, because the amount of water can be different depending on the environmental temperature. It is much better to touch the ground or check the amount of humidity of the substrate by lifting the pot, if it’s heavy it would be a good idea to irrigate it later.


It would be ideal to fertilize every two irrigation sessions, once with clear water and another one with water and fertilizer, the quantity of fertilizer will be indicated by the manufacturer.


I hope you have found these tips useful, if so please share this information with your friends. Don’t be lazy 😉

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Alan Martínez Benito
Alan Martínez Benito
CEO of Pev Grow, expert grower with more than 20 years of experience.
In constant struggle for the regulation of cannabis, mainly in the medicinal field.
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  1. Avatar for freddie longiamf

    amazing read thank you