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How to Grow Marijuana Indoors

Growing weed indoors has many advantages when compared to the risks associated of growing marijuana outdoors makes with threats from theft and possibly the law if it is illegal to grow where you live. By growing marijuana indoors you can control the ambient conditions just exactly as you want them and grow a nice healthy cannabis plant.

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Marijuana indoor growing and hydroponics

You can grow indoors without a full hydroponic system all you need are some good grow lights to replace the sunshine while placing your little seeds or seedlings straight into a pot of soil. This is the most basic indoor growing system and for simplicity it is still a great method. However, when most people think of growing marijuana indoors they think about using hydroponics.

Hydroponics is the name given to a variety of techniques for growing plants without soil. It was realized by researchers studying plant metabolism that plants took in their nutrients as simple inorganic ions, and that soil, while a source for such nutrients it was not essential. While a plant’s nutrients normally come from the soil, the only nutrients a plant can successfully absorb are those that dissolve into the plant’s water supply. When the required nutrients are introduced into a plant’s water supply artificially, soil is no longer required for it to thrive and that is hydroponics.

Grow room planning

Most growers will only have a specific amount of room available inside or within a weather proof area outside. We try to concentrate on the home grows for personal use who might want to grow from 2 to say 12 plants. There are numerous hydroponic growing systems available and lots of hydroponic grow boxes.

See our reviews on some of the biggest grow boxes from Dealzer and SuperCloset.

There are so many different types of hydroponic systems for growing marijuana indoors. From the basic wick method which does not involve any pumps at all to the more intricate aeroponics method with full misting emitters. We think that some of the easiest methods involve a little bit of trickery such as timers, pumps and maybe some aeration but it will be worth doing to have healthy roots which means healthy big buds.

1. Aeroponics – The roots of the marijuana plant is held in a water tight, dark box with small nozzles emitting a fine mist of nutrients over them. This gives a humid but oxygenated area for the roots to flourish in.

2. Continuous flow – Or the Top Feed system.

3. Deep Water Culture (DWC) – Roots of your plant are situated within the nutrient solution, however if it was left this way they would die from lack of oxygen so an air stone is added to oxygenate the nute solution and give the roots what they need to grow.

4. Drip Irrigation – A very effective way to grow with small emitters dripping the nutrient solution directly into the pot near the roots. This saves on water, evaporation is near zero and it is highly effective as the roots get nutrients and also air.

5. Ebb and Flow – The Ebb and flow system works with your plants sitting in a tray above a reservoir of nutrient solution. The nutes are flowed into the tray, the roots take what they need and the rest of the solutions flows back into the reservoir below.

6. Nutrient Film Technique (NFT) – Similar to the Ebb and Flow situation above but the tray is tilted so the nutrients are a thin film of liquid and constantly flowing past the roots.

7. Wick system – Very basic, see description above.

You will always have to watch your pH levels, pests and get your lighting and seed strains right of course. We find most visitors to this site are looking to grow a little to medium size grow and often the best course of action is to find a full grow box kit or grow tent which some with everything you need to get started.



Sea of Green (SOG)

SOG method incorporates how the Dutch masters create a fast yield in super quick time. They force the flower to flower at around two weeks old, it saves space and harvesting is far quicker. More info on Sea of Green.

Screen of Green (SCROG)

SCROG is very similar to the SoG method above and also extremely productive. The difference is using screens to spread the leaves out and give more of the plant light. More info on Screen of Green.

Low Stress Training

Growers train their crops by tying them down instead of topping or pruning them this is known as Low Stress Training. More info on LST training.

Marijuana seeds 

Selecting your marijuana seeds is an interesting part of the growing process. For those that do not have any access to clones first make sure you know the difference between Sativa and Indica strains.

  • Autoflowering marijuana seed strains have been around for some time now and are a cannabis seed strain perfect for indoors growing. Autoflowering seeds will not require the lighting to be changed from 24 hours down to 12 as they should still flower under 24 hour light, but usually it is best to cut the light down to 18 hour on and 6 hours off to help them flower really well.
  • Feminized seeds – We also suggest growers who can not get their hands on clones to buy feminized seeds. Feminized cannabis seeds are chemically treated so that they grow to become females. Feminized marijuana seeds are an excellent choice when considering growing marijuana indoors. Full marijuana seeds guide.

  • Buying marijuana seeds can be done online and there are a number of reputable companies that will send them worldwide. We say ‘reputable’ as over the decades we have only found certain companies to hold themselves out with excellent customer service, fresh quality seeds, discreet packaging and fast delivery. Some of the guys we like to deal with are:
  1. Herbies – Located in the United Kingdom they have over 2,500 different seed strains. They deliver worldwide, offer excellent customer service and we like them :-)
  2. Sensi Seeds – Of course are one of the oldest and most respected seed companies based in Amsterdam  The guys over there have spent millions of dollars on their seed stock production and they always offer amazing quality. They do not always send worldwide but you can usually buy their branded seeds from companies that do, like Herbies Sensi Seeds.
  3. Bonza Seeds – They ship worldwide, free discreet shipping, fully tracked delivery no signature required, delivery guarantee. Bonza mate!
  4. SeedsMan – Located in the UK and deliver worldwide with up to 30% off for bulk orders. Easy going guys who are good to work with and offer you guys great value for money.
  5. Marijuana-Seeds.nl – Based in the UK also, they do not offer branded seeds such as Green House, Barneys or Sensi but offer excellent quality white label seeds like Big Bud and White Widow. For fast, quality service and discreet delivery worldwide these guys rock.
  6. Cannabis-Seeds-Store  – These guys are UK based and offer great strains like Super Cheese Feminized and historically high 20.94% THC levels in Green House Seeds Jack Herer Feminized. Contact is excellent with CSSSeeds, they actually have a phone they answer and price match guarantee.
  7. MidweekSong.com – We still have no idea where the name comes from but we do know they pride themselves on worldwide delivery, awesome 24 hour customer service and discreet packaging.
  8. WeedPrices.com – They deliver a simply straight forward concept. They review only the cream of the crop cannabis seeds and tell you where to get the best deal on them.

Growing medium

This is the substrate that replaces the soil and what your plants require to grow in whilst using hydroponics. You can choose between many different mediums including Rockwool, perlite, clay pellets, cocos fiber or a combination of them. More info on growing medium 

Marijuana seed germination

This is where it all starts and one of the best methods for indoor growing is to the seeds off in a small amount of Rockwool, they then grow into the small cube which you then place onto the growing medium. The marijuana seedlings then grow straight through the rockwool into the substrate below. More info on marijuana seed germination.

Vegetative growth , pruning and flowering

Following on from germination your little seeds will start the vegetation stage of life. This when they require the more blue and green light spectrum from your grow lights. The vegetation stage can last from two weeks to many months depending on the strain and your growing method. For example using the Sea of Green method you would induce flowering in as little as two weeks. One you have you plants near your desired height turn the grow lights from 24 hours down to 12 hours on and 12 hours off  to induce flowering making sure that once it begins after around 10 to 14 days you identify the males (if you have not used feminized seeds) and pull them out of the grow room, read more here marijuana sexing. More information on vegetative growth and pruning then on to marijuana flowering.

Temperature and CO2

Getting the right temperature and mix of air so that your plants aren’t too hot, cold or humid is crucial for fast quality growing. When plants are too hot or do not get enough oxygen they start to droop and lose their color. Marijuana will tolerate temperatures between 60°F and 92°F (17°C – 33°C) however these are more the extremes. Their ideal holiday temperature is 70°F – 83°F (21.1°C – 28.3°C) and if you use CO2 you might need a higher temperature again.  Try and keep the temp around the 72°F to 77°F (22.2°C to 25°C) range through the whole growth cycle. The big HID grow lights such as HPS grow lights will produce around 5 to 6 times as much heat as LED grow lights, so if you use HIDs you must consider what ventilation system you will put in place.  More info on temperature, ventilation and CO2

Marijuana odor control your next indoor crop might use some amazing new cannabis seeds or even the original Skunk variety which is named so for a reason. It stinks! If you need to control the odor created by growing then you will have to pass the air out of the internal environment to the outside usually through tubing and an extractor fan. If the external area is too close to neighbors for example then you need to filter the air first using carbon filters, ionizers and ozone generators.

Hydroponic marijuana water pH

It is not always possible to simply use the hose and fill up the reservoir and leave it overnight. Some water will have higher acidic pH which is considered to be above 7.0 (distilled water) and some water will be lower and too alkaline. Usually it is best to let water stand for 2 or 3 days in another reservoir before use to help neutralize its pH. More info on hydroponic marijuana pH.  

Hydroponic nutrients

Most hydroponic nutrient solutions can bought from a hydroponics shop and marijuana, like all plants requires the basics, nitrogen (N), phosphorus (P) and potassium (K). You may recognize these letters from nutrient packs, (N-P-K) or in the format 10-5-5 showing it contains 10% nitrogen, 5% phosphorous and 5% potassium. More info on hydroponic nutrients.


Marijuana lighting guide


Basic Marijuana lighting guide

Lighting using the Nutrient Film Technique (NFT)

In this method, the plants grow through light-proof plastic films placed over shallow, gently sloping channels. A steady flow of nutrients is maintained along the channel, and the roots grow into dense mats, with a thin film of nutrient passing over them (hence the name of the technique). A downside of the technique is that it has very little buffering against interruptions in the flow eg: power outages, but overall, it is probably one of the more productive techniques.

You don’t need a lot of kit to start growing great flowering plants in a cupboard, wardrobe, attic or grow room. Apart from the seeds, the lamp is the most important item you will require. There are three main types used for growing light hungry plants. Metal halide (MH) which are one of the best HID grow lights for the vegging stage due to their blue / green light, high pressure sodium (HPS) which are decent all rounders but far better in the flowering stage offering light in the yellow, amber and reds. These days there are now full spectrum LED grow lights are an excellent choice as they can be used from seed germination right through to harvesting. Broad (full) spectrum LED grow lights cover the spectrum from 420 nm right through to 750nm which is the light spectrum that plants require for photosynthesis. LEDs usually cost more to setup when compared to HIDs but only suck down about 1/8 of the electricity as HID lights waste a lot on heat production. The top performing LEDs have excellent thermal parameters and run cold to the touch so you do not need hefty extraction systems or heat control, they do not have ballasts, can be placed 18 inches from the top of the canopy so save on space and are cheaper to run with bulbs that last far longer. More on marijuana lighting.

Basic kit using grow pots or NFT tank

  1. LED full spectrum grow lights with a total output of approximately 50 to 250 Watts or a high pressure sodium lamp (600 Watt is the most efficient but a 400 Watt may suit a smaller space);
  2. Fan and ventilation exhaust systems running 24 hours a day if possible. No need with the LEDs as they produce very little heat;
  3. Buy some seeds and now you have seedlings in pots situated in your tray using your chosen grow medium. Try a basic mix of 50% potting compost 50% Perlite. Raise the pots in the trays with bricks or wood so they don’t sit in a puddle once watered, they need drainage to keep oxygen flowing and help them grow. OR. NFT tank with pump and spreader mat (these come with the tank), Rockwool cubes.
  4. 24 hour timer to control light cycles. This should be used with a high power switch known as a contactor or relay switch as grow lamps can easily burn out regular timers used on their own;
  5. A pH tester to test water and nutrient feed solutions to adjust water and feed solution to around pH 6.0 – 7.0;
  6. Nutrients, ones aimed at growing the plant during the vegging stage and then usually a different solution when it comes to flowering or budding;
  7. Matt white paint or white plastic to cover the walls of the grow space to help reflect light back onto the plants.

Also useful are a measuring bucket, measuring jug, large syringe and pea netting or string to support top heavy plants. If you can afford it a great help is a Total Dissolved Solids (TDS) meter. These allow you to check the nutrient levels of feeding solutions to make sure they are optimised for your plants.

Growing hydroponically in a Nutrient Film Technique (NFT) Tank is really simple and not something to be afraid of. In fact some beginners to growing may find it easier than using soil mixtures in pots. You do not have to judge if the plants need watering or feeding so much using NFT, as long as you follow the simple instructions supplied with the tanks the plants should look after themselves.

Also useful is a measuring bucket, measuring jug, large syringe and pea netting or string to support top heavy plants. If you can afford it a great help is a Total Dissolved Solids (TDS) meter. These allow you to check the nutrient levels of feeding solutions to make sure they are optimised for your plants.


Wherever you decide to set up your grow space remember that the plants night time or dark period is very important. Check that when the light goes off the grow space is in total darkness. Proper ventilation for the grow space should also be considered as the area can become very humid. Opening up the space daily may be enough but larger areas may need extactor fans to avoid problems. Please visit Legalize Marijuana and show your support for the cause.

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From the forum

How to Grow Marijuana Forum - Growing Marijuana Indoors & Hydroponics

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72 thoughts on “How to Grow Marijuana Indoors

  1. Wanna learn how to grow seeds. Thanks for letting me join your web site.

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  2. reno says:

    i have 3 plants 3 weeks after sprouting sitting on window sill with day light and night, ive just put them under 24 hr fluro light wile getting a indoor room ready. will this stress out the plants at such a young age? any help would be appreciated. melbourne australia. new to growing


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  3. Vaper1306 says:

    I germinated my seed right, put into organic soil less mix, have had it on my west facing windowsill for five weeks now and it’s starting to reek a little bit, how much longer do I keep in small pot before transplanting to a larger pot for more root room? And I’m supposed to keep the light cycle @ 18/6 or 24/7 until the 24hour shock that begins flowering phase? Imma first time grower and I’m tryna keep it organic, high-yielding, high THC, and indoors.

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    Rating: +2 (from 2 votes)
  4. Soumua says:

    Hi so i am a new grower and i have one plant that is developing yellow leaves but its not a burn fron nutrition because i havent added any and the leaves dont turn brown they become yellow and dry out any suggestions???

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    • Chris says:

      I would add some epsom salt. 1 teaspoon per gallon. You NEED to add nutrients also, thats the plant food.

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    • I would say to much water that’s what a tomato plant does on the bottom when u water to much

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      Rating: +3 (from 3 votes)
    • barry says:

      I assume you are using soil? Sounds like your ph is off in your soil and you should be adding some sort of juice to your plants. Could be your plants are trying to tell you something. If you want to get a good harvest it makes a huge difference. I over juiced mine (2 days in a row) and got every tip on every leaf brown and dying (curling up) on me.
      My male plant that I had outside I did not give any juice to and it turned all yellow and died on me.

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  5. John says:

    I am new to growning, dont have access to plant food or fertilizers. Need some help figuring out on what type of home remedies to feed my weed plant. By home remedies i mean regular store bought food products that we have. Please help, Also need instructions on how to have a structured watering time along. Please Help!!!

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  6. chris says:

    My leaves are wilting almost looks like claws the way the smaller leaves look.. Any help?

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  7. lil-bro says:

    Ok I have 6 plants and they are 7 inches and 2 weeks I wanna know am I growing them right

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    Rating: +1 (from 9 votes)
  8. donnie says:

    First time grower indoor 1000 watt light hps light on one Clone clone in my closet. 8 weeks left of flowering. Its growing great but I want to be sure I max yield on this plant. What steps could I take more to ensure productivity and mass? Tips? How much do I water?

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  9. mann says:

    How do u grow weed?

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  10. mary says:

    hi can anyone please tell me how buds loose there THC level and become like hemp,lol,i have cloned many time from the same strain at the beginning smoke was really good but over time the THC has deminished is there such a thing as over cloning,or is there another reason for this happening

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