Growing cannabis indoors

Growing cannabis indoors

Growing cannabis indoors is easy. You can buy everything you need online, or from your local garden centre / grow shop. Don’t worry if you have never grown cannabis indoors before, it’s not complicated and most people can master the basic skills quickly. Read on to learn more about:

  • Choosing the best cannabis seeds
  • Germinating cannabis seeds
  • Grow lights for indoor cannabis growing
  • Nutrients used for cannabis growing
  • The importance of the climate in your grow room
  • Tips for growing cannabis indoors

New to growing cannabis indoors?

Don’t worry. Growing cannabis is easy. Cannabis grows in a wide variety of substrates and under a broad range of conditions. If you are looking to grow a few plants in a square metre tent, then any of the Dutch Passion autoflower seeds would be a good choice for an easy grow. Feminized varieties such as Night Queen, Mazar or Bubba Island Kush would also make great choices.

The Dutch Passion cannabis seed collection is one of the most complete seed catalogues ever assembled. You will find a wide selection of cannabis cup winning varieties in several categories.

Feminized seeds and autoflower seeds

Most people grow cannabis indoors with feminized seeds or autoflower seeds.

Feminized seeds grow vegetively for the first few weeks under 18 or 24 hours of daily light. They only start to bloom when daily light is reduced to 12 hours, and generally take around 8-12 weeks to bloom. Some varieties/phenotypes can be quicker and ready after as little as 7 weeks of bloom. Fast blooming varieties are probably very Indica dominant, such as Bubba Island Kush. Some Sativa dominant plants/phenotypes can take up to 15 weeks to fully finish blooming.

Autoflower seeds grow from seed to harvest in around 75 days under 20 hours of daily light. Many people find them the easiest, fastest and most convenient way to grow cannabis indoors. Less experienced growers often find that autoflower seeds are one of the easiest and most straightforward ways to start growing cannabis. Autoflower seeds grow under any light schedule indoors or outdoors. They tend to reach around a metre tall for most indoor growers and produce heavy harvests of strong cannabis.

In general, cannabis seeds with indica genetics tend to produce shorter plants, and sativa varieties tend to be slightly taller and can stretch more during bloom. Sativa dominant varieties also have a longer life cycle than Indica dominant strains, both for photoperiod and autoflowering plants.

CBD rich cannabis seeds Produce cannabis that contains 4% CBD (or more) in the dry buds. These are popular with medical growers, the high may not be quite as intense as a typical THC rich variety. You can get CBD rich cannabis seeds as both autoflowering and feminized photoperiod options.

Regular Seeds. These give rise to female and male plants in roughly equal quantities. They are often used by old-school growers or those looking to select parent plants for subsequent crossing. New growers tend to avoid using regular seeds. For less experienced growers, feminized seeds are a more convenient and simpler option.

Choosing the best cannabis seeds for growing cannabis indoors

Best seeds for growing cannabis indoors

Choosing a cannabis variety is of major importance. Yields and quality of plants grown under artificial lights mostly depend on:

1. Seed variety
2. Whether the plants are grown from seeds or clones
3. After how many days of growing the plants are put into flowering
4. Optimization of the climatic conditions of the grow-room.

Apart from “true breeding” varieties, our seed collection consists of different F-1 hybrids. Crossing two “true breeding” strains (hybridizing) gives F-1 hybrids that possess the so-called “Hybrid Vigor”. This means that the F-1 generation is a lot more potent than either parent. F-1 generations also consist of uniform plants.

How to germinate cannabis seeds

Germinating seeds for growing cannabis indoors

Germinating cannabis seeds can be done in various ways and the internet is full of cannabis grow forums that document various methods. The Dutch Passion cannabis seed germination guide lists several of the most popular ways to germinate seeds. One simple method is to simply place seeds about 1cm below the surface of firmly pressed damp soil. A film of transparent kitchen film over the surface helps keep conditions moist and after a few days of temperatures around 20-25°C the seeds should germinate. Growing from cuttings of mother plants is an alternative to growing from seeds.

In the first stages of life the seedlings are happy to start with lower light intensities often a metre below an HPS light (much closer for fluorescent lights, perhaps 20-25cm). The artificial lights are normally on for 18-24 hours per day. During this time the seedlings are in a state of vegetative growth, they will continue to grow roots, leaves and branches but no bud.

Putting your plant into flower mode, and harvesting the end result

By reducing daily light to 12 hours the feminized cannabis plant transitions into the ‘flowering’ phase. This stage normally requires 8-10 weeks (but more for certain strains) and it is during this time that the female flowers form. During this stage the plants grow heavy blooms and will tolerate more nutrients and very bright light. Some growers introduce supplemental lighting to ensure the very best yields. At the end of this process the plant is cut down and the buds (un-pollinated female flowers) are dried. Some growers harvest the plants when they see the trichomes starting to transition from clear to cloudy (this requires a magnifying glass). This often coincides with the bud producing lots of red/orange pistil hairs. Some smokers prefer bud harvested early, others prefer late-harvested bud. When you grow your own cannabis indoors it is you that decides exactly how you like it!

In general, longer periods of vegetative growth will grow larger plants and support greater yields during subsequent flowering. Typically, 4-5 weeks of vegetative growth are used and during subsequent flowering the plants may increase to 2 or 3 times their original height. Some growers use the ‘sea of green’ (SOG) method, this uses just a few days of vegetative growth before switching to ‘flowering’ conditions. This technique produces small plants of low/medium yield but allows for fast production. With enough plants per m2 you can still get great results.

Grow lights for indoor cannabis growing

Cannabis loves light and the successful indoor grower tries to deliver as much light as possible. Consider 250 watts/m² only as an absolute minimum starting point and realistically aim for 2-3 times that level. More light will mean bigger, denser buds and superior yields. As well as delivering high light levels the successful indoor grower keeps the plants close to the light to maximise the light intensity reaching the leaves and buds. It is important to be careful, put the plants too close and your plants will get light burn. This can appear as white tips on the flowers/buds – or weird looking leaves during veg. Often the personal medical or recreational indoor cannabis grower will have a growing tent of about 1.2 m² with a 400W or 600W high pressure sodium (HPS) lamp or an LED light using around 300-600W.

The indoor cannabis grower has to be careful that the plant doesn’t grow too near to the hot light and damage itself. If the light feels cool to the back of the hand it will be cool for the plant also. For a 400W lamp, growers may not want to allow plants to grow within 40-50cm of the bulb. Cannabis plants can be bent over and tied if they get too tall, some indoor growers deliberately train their plants this way to get as much of the plant as possible close (but not too close) to the high intensity light.

If you are buying an LED grow light we recommend the website of LED By Passion, our sister company. All the grow lights have been designed for growing cannabis, the grow lights have all been tested and approved before being added to the collection. The worlds best LED grow light brands are all represented.

Certain strains respond well to having the growing tip of the plant pinched out (known as ‘topping’, ‘FIM’ or pinching) after the 4th or 5th leaf pair. The resulting plants are often smaller and bushy without the dominant main growth stem (or ‘cola’) and are preferred for some smaller growrooms or for growing techniques like SCROG.

Nutrients used for cannabis growing

Growing cannabis indoors will require use and understanding of plant feeds. This is not complicated, all the plant food does is deliver essential nutrients to the roots, it doesn’t matter whether the roots are growing in clay pebbles, rock-wool, coir or a hydroponic system. Even soil-grown plants will need additional nutrients when the soil has been depleted. Read the instructions on the nutrient labels and avoid the beginners temptation to exceed recommended levels. The experienced gardener can ‘read’ his plants and will learn when to water and feed plants. If you see the tips of the leaves turn white or yellow, than this is the first indication of an excess of nutrients, when they go brown and crispy it could be due to over-feeding. If this happens reduce feed concentration immediately and consider flushing with water for several days.

Mineral vs organic nutrients

Mineral nutrients are often used by hydroponic growers in automated systems. They won’t clog up the pipes and dripper lines used in some automated hydro feeding systems. The nutrient minerals are dissolved in a water solution and are usually clear, transparent fluids which contain all the necessary minerals for growth.

Organic nutrients are a little different. The nutrition may be delivered as materials which will decompose and break down in your grow medium. This may allow gradual release of nutrients. Organic nutrients may be supplied in solid form, for example BioTabs manufacture organic nutrients made from insect/animal products. These solid feed supplement tabs are simply placed in the soil and breakdown naturally ready for the cannabis roots to absorb them. Organic nutrients are also available in liquid form. Often the liquid organic nutrients bottles will require shaking to disperse any settled solids at the bottom. Organic liquid nutrients are often not recommended for certain hydro systems since they may eventually clog up the pipes used to pump and deliver nutrients.

Biotabs for Snowbud variety
Biotabs for easy growing

Nutrients purpose designed for soil and coco

When growing in soil, especially in large containers of soil, there may be sufficient nutrients for the first few weeks of growth. That means you may only need to buy a bloom nutrient designed for soil growers. If you grow in a small container of soil, then you may also need a soil-based nutrient for veg growth too.

Those growing in coco fibre will see dedicated nutrients for coco. Often this will be as simple as a 2-part coco ‘A’ and coco ‘B” solution. Coco fibre is light and airy, cannabis thrives when growing in it. Some people add coco fibre to their soil to improve soil structure and aeration.

Nutrient pH

pH is simply a measure of acidity for a given liquid. For soil growers using organic nutrients it isn’t really necessary to worry about pH. This makes organic growing simpler and fuss free, ideal for new growers. Organic nutrients such as BioTabs are simple to use, and because it’s organic the plants are less likely to overfeed. The soil acts as a natural buffer making it more resistant to rapid changes in nutrient content and pH. Even if a nutrient build up does start to happen in an organic feed system it happens slowly. This allows the grower many weeks to notice and deal with it. By contrast, in a hydroponic system the plants can be immediately affected if you e.g. add too much nutrition or use the wrong pH.

In a coco or hydroponics cannabis grow, the grower will often have the pH of his nutrient feed set at around pH 5.8. If the pH is set at the wrong value, the plant won’t be able to absorb the nutrients even if they are present. So, an incorrect pH in your feed solution can confusingly result in nutrient deficiencies even though your nutrients contain all the necessary minerals. When using a pH meter, check and calibrate regularly to ensure it is providing valid readings. The best growers always have a spare pH meter for the inevitable time when the pH meter fails.

Electrical conductivity, or E.C.

EC meters are used by growers to give them an indication of the electrical conductivity of their nutrient solution. This in turn measures how much mineral content there is in the nutrients. The more minerals in solution, the higher the electrical conductivity. Experienced growers always have a fully calibrated and checked EC meter for each batch of nutrients that they make. They also usually have a spare EC meter for the moment that their main meter fails. The experienced grower combines their own plant knowledge/experience with the nutrient manufacturers recommendations to prepare their nutrient feed solutions. For small plants the solution is weaker. As plants age, the nutrient solution needs to become more concentrated with a higher EC reading. Note that EC doesn’t actually measure which useful minerals are dissolved in solution, it simply measures the total mineral content in the water.

Indoor growing allows the plants to develop under closely supervised grow conditions without the normal array of outdoor pests and bad weather. Once the grower has the right indoor system in place it is a predictable way of growing great quality cannabis, a lot better than weed sold by street dealers. The main challenge for many indoor cannabis growers is dealing with the characteristic cannabis smell so that no-one notices it. Ensure your carbon filter is working well and replace it if it isn’t.

Recreational and medicinal cannabis popularity now extends far outside the earths warm/tropical climates. So, for many people, growing cannabis indoors is the only option. Growing cannabis indoors has never been as popular as it is today, nor has it been as easy to produce superb quality weed. Professional cannabis seed suppliers, equipment providers, advice and information are all available on the internet.

The importance of the climate in your grow room

One of the most important factors in your grow room is the climate. You can have the best cannabis seeds and equipment. But if your temperatures and humidity are wrong you will struggle to grow the best quality cannabis. Experienced growers aim for a stable optimized grow room environment. Rapid temperature swings or extremes should be avoided. Some indoor growers use the ‘lights on’ period for the coolest part of the day, for example after sunset when ambient outside temperatures are cooler. Use of an exhaust fan with a temperature control is one technique which can help. With the use of a climate control device you can set a maximum grow room temperature, e.g. 27ºC. Once this temperature is reached, the exhaust fan speeds up to maintain temperatures.  If the grow room temperature stays naturally below your pre-set maximum the grow room uses less energy and less extraction.

LED grow lights and climate control

One of the most popular grow room technologies for quality conscious growers is LED. The best LED grow lights use an optimized light spectrum and produce far lower levels of ambient heat than older HPS lighting technology. LED produces higher cannabinoid and terpene levels, it’s the choice of professional quality-focussed growers around the world. Many growers prefer LED because it emits less heat than HPS. This makes it easier to control and optimise your grow room conditions with LED than HPS. Less extraction, and less air conditioning is needed. Less energy is used and superior quality buds are produced from LED. HPS produces a lot more heat to get rid of, and in summer time with high ambient temperatures, it can be very difficult to control temperatures in an HPS grow room. Once grow room temperatures exceed 30ºC it becomes difficult for the plant to grow in an optimized way. Quality and yield are both adversely affected. Serious cannabis growers invest in air conditioning for their grow rooms to prevent maximum temperatures reaching damaging levels.

Grow Room location and heat/climate control

Many people grow in their attics. However, in summer the high temperatures can be damaging for the plants. Likewise, in early spring, the night time temperatures in an attic can be too low. Avoiding extreme temperatures, and large temperature fluctuations improves cannabis quality and plant health. It could improve conditions if the grow room could be relocated from e.g. the attic to the cellar or a spare bedroom at certain times of the year.

Humidity and cannabis climate control

Humidity is also a crucial factor for the cultivation of quality cannabis. During early vegetive growth it is best to keep humidity at higher levels than during flowering. For vegetative stages humidity is usually kept around 60-75%. For clones that have not rooted yet keep humidity very high, about 85-90%, best way to do this is by using a dome (mini plastic greenhouse). Once bloom has been underway a few weeks, lower the humidity to about 50-60%. For the first 2-3 weeks this should be fine. As you reach the half-way mark through bloom, buds are forming and it can help to keep humidity under 50%. As you go into the final weeks of bloom, lower humidity even further to 35-40%. This will reduce the chance of mould and fungus and will harden your buds. You can control humidity by using a humidifier and/or de-humidifier.

Tips for growing cannabis indoors

Growing cannabis indoors has seen a dramatic rise in popularity in recent years. When done properly it produces excellent quality cannabis which is usually much better than that sold on the streets.
Growing cannabis indoors relies on the use of powerful artificial lights to replicate the effect of the sun. The ‘average’ home grower has a 1.2 x 1.2m tent (or similar) and usually has a light between 100-1000W. The 400W and 600W HPS grow lights have been favourites with indoor cannabis growers for many years. More modern LED grow lights produce better results, with higher THC levels but at a higher cost. A carbon filter and extraction fan are essential items for any indoor cannabis grower. Your local grow shop, or an online supplier will have all the necessary equipment and usually can provide good advice. They will also supply nutrients.   

Growing cannabis indoors at home

Some indoor growers train the plants underneath a metal wire mesh screen allowing only the buds to grow vertically while the stem and growing part of the plant are trained horizontally. This SCROG (screen of green) technique allows the indoor grower to keep as much of the bud growth as possible equidistant to the lamp, maximising the efficiency and yield.

Specialist suppliers offer ‘air cooled’ lights for the indoor grower that enclose the light in a glass casing. A fan forces air over the light and outside the grow-room via tubing, keeping the grow room cool and allowing the plants to grow taller without burning. Grow rooms are typically kept around 25°C for optimum results. Higher temperatures can cause the plants to wilt and cooler temperatures may slow down growth. The plants will need a gentle breeze from a fan, and a steady supply of fresh air which can be from your house or from outside. Stale air from the grow room is normally continually extracted outdoors by a fan and the pungent cannabis aroma is removed with a carbon filter.

Those indoor growers that do get caught are often betrayed by the smell of their grow room, so some people also invest in ozone generators to further remove odours from the exhausted grow room air.

Indoor grow box

Choose feminized seeds for indoor growing

Feminised seeds are popular with the indoor growers as they virtually eliminate the possibility of male plants. For many indoor growers feminised seeds from a quality supplier are regarded as the only way to grow.

Male plants are nearly always destroyed by the indoor grower as they don’t yield any buds, and given the chance they will pollinate the female plants reducing them to seed.

The indoor grow-room allows plants to be grown in soil or any number of other grow mediums. When growing in soil the cannabis plant benefits from 25% perlite or coco fibre being included. This allows better aeration of the soil and more oxygen for the cannabis roots. One common mistake by inexperienced growers is the tendency to overwater/over-feed soil-grown plants. Get to know the weight of your plant pots and water only when the plants need it. Over watering soil-grown plants will reduce yield/quality and slow down plant development.

If you want a tool to help you pinpoint the exact time to water your plants then consider buying a tensiometer. This is a device that will precisely measure the moisture level in your soil. With this you can give your plants the exact amount of water they need, when they need it.

Macro shot of Bubba Island Kush

Indica versus sativa versus hybrid cannabis seeds

Before you buy your cannabis seeds consider the differences in the way they grow and the types of bud/high produced.

Indica cannabis seeds often tend to produce more compact plant growth, bushy and short. These can be ideal for the grower with limited head room or smaller grow tents. Indica plants often show broad leaves with wide fingers. The stems tend to be short, strong and stocky with a large main bloom but sometimes not so much side growth. Indica buds tend to be hard, compact and with relaxing sedative properties with a fast acting high and strong body effects. Indica’s often take between 7-9 weeks to complete bloom, making them faster than many sativa varieties. The buds tend to be firm and easy to trim. Indica’s are known to handle a higher nutrient feed easily. This traditionally makes Indica’s and Indica dominant hybrids more suitable for inexperienced growers

Sativa cannabis seeds generally produce stretchier plants which may require taller grow rooms. Some growers use the more slender and stretchy plants for filling out a SCROG screen. The flexible branches are easy to manipulate and bend in a SCROG screen. This is a good way of using just 1 or 2 plants to fill a small/medium grow area with buds especially with a little extra veg growth. If you grow sativa plants in a sea of green (SOG) system they can be flowered immediately, often under a 12/12 light system to help control final plant height. Once in bloom a sativa plant can take 10-15 weeks to complete the flowering process and fully ripen. Sativa blooms, which have evolved in intense light levels with hot humid conditions, often have a more open and airy bud structure to grow with reduced chance of mold. This can make the long sativa blooms a little more time consuming to cut and manicure properly. If your climate is hot, humid with strong light levels then a sativa variety may adapt better to the conditions than an indica. Conversely, an indica variety may suit you better if your conditions are a little cooler with lower humidity.

Sativa varieties can be a bit more difficult to grow than an indica. Some sativa varieties can be fussy with nutrients/feed solutions. For more experienced growers this really isn’t an issue. However, some less experienced growers may prefer to avoid a stretchy Sativa and gain more experience with indica and hybrid varieties before opting for a sativa variety Hybrid cannabis seeds combine the best of both worlds, with indica and sativa genetics. Sometimes you will see plants lean more towards a sativa or indica parent. Often you will see the plants show characteristics of both parents. With a hybrid cannabis variety, the bloom time is often between that if indica and sativa varieties, around 8-11 weeks. With a hybrid variety you enjoy bloom times which are not excessively long, you also enjoy good yields, compact buds and a pleasing high with elements of both indica and sativa. For many growers, these are the reasons why good quality hybrid varieties are some of the most sought after in the cannabis seed world.

Get cannabis seeds online

Successful indoor cannabis growing begins with the best cannabis seeds – get them from a supplier you can trust. The price difference between the best seeds and budget seeds is small in comparison to the value of the cannabis which is produced. Dutch Passion have been in business since the 1980’s supplying the best cannabis seeds with the highest THC levels and the most pleasurable highs. You can buy feminized seeds online from Dutch Passion, or you can buy autoflower seeds online. Both cannabis seed types are easy to grow and will deliver heavy yields. Dutch Passion also sells regular cannabis seeds. Buy Dutch Passion cannabis seeds online and you get decades of expertise and some of the best cannabis genetics available.

10 Comments. Leave new

  • Boitshwarelo Pico
    14/06/2020 18:04

    How close to put growing LED lights

    • It depends on the type/power of LED light you have, if its powerful start at 65cm for veg and bring it down to 45cm for flowering.

  • Rajeshwar Dayal
    10/10/2020 18:26

    More Blue light increases the number of female plants ?

    • We have not worked with this technique yet, but there are indeed theories out there that blue light in the vegetative phase could increase your numbers in female offspring.

      Dutch Joe

    22/12/2020 14:45

    There is some excellent advice in this article. Dutch Passion has been producing world class genetics for decades. Whether you are growing indoor or outdoor, Dutch Passion will have seeds to fit your needs =)

  • where can I find the black and green pot in the header or first image?

    • Hey,

      This is an airpot, you should check for yourself what the best options are to buy these 😉

      Dutch Passion

  • Michellis
    09/02/2021 17:31

    Is it possible to explain when the veg state stops and the flowering state starts. I suppose the answer is in the question, but I’m a little unsure…?

    • Hey,

      I am not sure if you mean with autoflowering or photoperiod varieties.

      But with photoperiod varieties the flowering period starts when the lights are switched from a 18/6 to a 12/12 light schedule.

      Autoflowers will start to flower automatically.

      Dutch Passion

  • Mike Mitchell
    11/02/2021 03:04

    I’m a first time growerAnd this was very informational for me


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