In this post we show you a grow report of regular cannabis seeds for those growers who want to use these seeds in their crops. Learn the small differe Growing weed indoors is a great option for new homegrowers. Learn everything you need to know about growing weed indoors, including how to set up your grow room and climate control. Growing marijuana indoors isn’t as impossible as you might think. Learn how to grow plants inside with this step by step guide with infographic.
Growing regular cannabis seeds indoors
Contrary to popular belief, growing regular marijuana seeds (in which we find male and female plants) isn?t more difficult than growing feminized seeds. They are accessible for everyone, also for beginners. Until early 2000, everybody learned to grow marijuana using regular seeds and the selection of female and male plants was just another step of the grow, something fast and simple to realize, such as the germination process or switching the photoperiod.
Conspiracy Kush from TGA Subcool
Naturally, 50% of the regular seeds are males and the other 50% are female plants. Of course, several factors can alter this ratio, but if using more than 10 seeds it’s almost impossible not getting a single female plant (the chances of getting 10 males out of 10 seeds is lower than 1:1000). Some people think that environmental conditions might influence on this male / female ratio (good conditions usually bring more females), but this theory hasn’t been verified in a rigorous way yet.
So, generally we recommend you to germinate 15 or 16 regular marijuana seeds for every square meter in small flowerpots. Grow them for few weeks and then switch to bloom, right before removing the males and transplanting the female marijuana plants into the definitive containers. Normally, we use 6-10 plants per square meter during the flowering stage.
In this article we will show you a grow report of 16 regular seeds using a 90 x 90 cm (or 81 m2) grow tent. The crop took around 3 months (from early October until late December). We gave our plants a growth period of 3 weeks and, approximately, 10 weeks of flowering.
Equipment for the crop, nutrients and marijuana strains
This indoor crop was performed in a DarkRoom V2 90 grow tent, with a 400W HPS bulb for the flowering phase. We used organic nutritients from the following brands: Aptus, General Organics, BAC and Cannabiogen:
- Growth Fertiliser: Bio Thrive Grow (General Organics)
- Bloom Fertiliser: Organic PK Booster (BAC)
- Growth Stimulator: Start Booster (Aptus)
- Bloom Stimulator: Top Booster (Aptus)
- Regulator (Aptus)
- Delta 9 (Cannabiogen)
Feeding chart for this crop
The beneficial fungus Trichoderma Harzianum, which grows in symbiosis with the roots of the marijuana plant, was used in each watering throughout the crop. We would like to stress the importance of using Trichoderma from seedling and also after each transplant. Trichoderma allows you to protect the roots from attacks of fungal pathogens and improve the nutrient uptake by the roots.
The Organic PK Booster from BAC contains P&K (Phosphorus and Potassium), as well as Nitrogen (N) and all the essential micronutrients needed by the plants, so it?s possible to use it as complete organic flowering fertiliser for your marijuana plants. It also contains sugars (molasses) and other interesting natural ingredients.
We used Light Mix with a bit of Bio Super Mix to enrich the soil composition. The chosen cannabis strains to grow were:
- 8 regular seeds of Conspiracy Kush from TGA Subcool, a mostly Indica cross between Obama Kush and Space Queen.
- 8 regular seeds of 818 Headband from The Cali Connection, a hybrid of Sour Diesel and OG Kush, two famous geneticsfrom USA.
Germination of cannabis seeds
16 marijuana seeds were set to germinate between two dishes, using paper towels moisturized with water and Trichoderma.
Germination of cannabis seeds
You should make use of the microbial life as soon as possible so that the symbiosis will be effective from the beginning and the small radicle is protected against the attacks of fungi and diseases such as the Phytium or wilting. Normally, it will be possible to observe the development of the Trichodermas on the roots.
Keeping the temperature between 20 and 25° C, 100% of the seeds sprouted within 48 hours. They were planted into 3 litre pots during approximately 3 weeks of growth. It?s possible to use smaller plant pots during the first days of the plant’s life to create a more dense and effective root system.
Seedlings beginning their life
Growth of cannabis plants
From the beginning of the growth period we could observe traces of thrips in the youngest leaves, noticing the silver dots typical of this pest. We soon used a treatment using biological insecticides, spraying the plants with this mixture:
- Azaprot (Neem Oil) 2 ml/L
- Pireprot (Crisanthenum Pyrethrum Extracts) 2 ml/L
- Cinnaprot (Cinnamon extract) 2 ml/L
- Alliumprot (Garlic slurry) 6 ml/L
If you want, you can replace the Azaprot, Pireprot and Cinnaprot from Ecoprotec for Trabe’s Ain THC, Expelex and Bio Fungi C Grow.
Cannabis plants after 6 days of growth
Generally, when using natural insecticides, we recommend mixing different active ingredients to prevent insects, diseases or mites, thus improving the plant resistance from the start. This mixture allows you to fight with natural methods against a great diversity of insects and mites, using it either as preventive or to erradicate pests.
Cannabis plants after 12 days of growth
During the second week of growth, we stimulate the vigour of the plants spraying 5 ml/L of Delta 9 from Cannabiogen, a product rich in vitamins, amino acids and nutrients. After around 15 days since the beginning of the plants life, we start adding growth fertiliser (Bio Thrive) to the nutrient solution, gradually increasing the dose while looking for nutrient excesses.
Cannabis plants after 16 days of growth
During the last week of growth (3rd week), we apply another insecticide treatment before switching to bloom. At this point, we prune the tops of the plants to keep their vertical growth under control, what will also be beneficial for the development of side branches.
Cannabis plants after 21 days
During this growth period, the temperature varied between 22 and 31 ° C, while the humidity level was between 40 and 70%. At early Autumn the weather can be really hot in Spain, and the humidity level raised as the plants grew.
Pre-flowering of cannabis plants (weeks 1 and 2 of flowering)
The growing space was full and it was time to switch our plants into the flowering phase, reducing the growth photoperiod – 18 hours of light per day (18/6) – to 12 hours of light per day (12/12).
We divide the flowering stage in three consecutive phases, and each phase must be performed perfectly to ensure a good harvest. These phases are: the stretch, the bud development and the final ripening of the plants, the last stage before the harvest of marijuana plants.
When we switch to 12/12, the stretch period begins and plants grow notably until reaching their final height, a phenomenon comparable to the adolescence of humans. During this period, cropping the branches of the higher plants – trying to keep them as uniform in height as possible- is advised.
Cannabis plants after 4 days into flowering
While marijuana plants are normally very vigorous and very resistant during the flowering period, this is a crucial moment for them and the grower should take care of their needs properly: if you don’t look after your plants during this stage, you will take the risk of creating a jungle very difficult to control once in full bloom, especially when working with different genetics.
The watering and feeding needs (especially Nitrogen) must be accurately met during the stretch of plants, so we must pay close attention to prevent any drought or deficiency which would slow down the overall plant development. During the transition to flowering, we used again Delta 9 from Cannabiogen (via foliar), to help and stimulate the plant metabolism during this important stage.
Cannabis plants after 8 days into flowering
Few days after switching to 12/12, we could already identify the female plants for the two pistils (white hairs) that develop on the internodes of the branches, so we could easily identify and remove the male plants, which develop very different flowers, shaped like small clusters or sacks.
In this crop, we got the following number of males and females:
- Conspiracy Kush: 7 female plants, 1 male plant
- 818 Headband: 3 female plants, 5 male plants
Thus, we had 10 female plants to flower, which were quickly transplanted into 7 litre pots. We pruned the lower parts of the plants to favour the top parts, which are more exposed to the light. These small branches were rooted as cuttings in a small propagator (during the growth cycle, 18/6), so we could keep an exact copy of each grown female.
After the harvest, the tasting will allow us to choose the best female according to our criteria (taste, smell, effect, yield, resin production, resistance to pests, etc.) and keep them as mother plants, so we can grow the same plant again and always with the same traits. Indeed, regular seeds are the perfect option for selecting mother plants.
Cannabis plants after 15 days into flowering
Right after the end of the stretch, all plants were treated for the last time with a biological insecticide. If you want to make your own regular seeds, you can also select and keep the best males in a separate space. If you don’t want to make seeds, then you should remove them as soon as you identify them to avoid that they release their pollen and get your plants seeded.
During the stretch the temperature ranged from 21ºC to 28ºC and the humidity level was between 40% and 60%.
Cannabis plants in full bloom (3rd and 4th weeks)
As soon as we see that our plants are starting to develop buds we can stop using growth fertiliser and root stimulators, which will be replaced for nutrients and boosters formulated for the flowering stage.
Cannabis plants after 3 weeks into flowering
A third and last application of Delta 9 will stimulate the metabolism of the plants for the next weeks. The stretch phase has finished, except for one 818 Headband from The Cali Connection plant that keeps on growing. We continue cropping it regularly and place it on a corner of the growing space.
The flowering was slowed down due to low temperatures, so we added heat cables around the pots: the roots of cannabis plants are sensitive to cold and we must warm them if necessary. Just like us, marijuana doesn?t like cold feet. We decrease the potency of the extraction fan with the help of a power controller to keep the heat produced by the lamp in the growing space.
After these changes, the temperature ranged from 12 °C (light off) to 20 °C (light on) and humidity ranged between 50% and 70%.
Cannabis plants after 4 weeks into flowering
At this stage of bloom the buds are beginning to develop a considerable amount of resin, and the smell is more and more intense, so using carbon filters is advised if you want a discreet crop.
Peak of flowering (5th and 6th weeks)
At this moment, the Conspiracy Kush plants from TGA develop beautiful bluish colors favoured by the low temperatures during the night periods. We keep on using our feeding schedule and any plant shows symptoms of deficiencies during this stage, in which the buds fatten up day by day.
Conspiracy Kush after 35 days into flowering
Once into flowering, marijuana plants need very little maintenance, but we should look with diligence for the presence of insects, mites, fungi, deficiencies and excesses or hermaphrodite plants.
At this point, the temperature ranged from 14 to 25° C and the humidity from 50 to 70%. In some Conspiracy Kush phenotypes the resin production was excellent, as well as the superb scents released by the more resinous plants.
41 days into flowering, we start flushing the roots (weeks 7 and 8)
Flushing the roots of cannabis plants (7th and 8th weeks)
The dosages of the nutrients and boosters used have been progressively reduced so that washing the roots of the plants is performed more progressively and effectively. The plants will now use the nutrient reserves they’ve kept in their tissues, principally in the leaves but also in other parts of the plant. Flushing the roots highly improves all the aspects of the final product, improving both the organoleptic features and its medicinal properties.
47 days into flowering
At this stage, the buds stop growing; the plants start their ripening process, the last stage of the flowering period; the flowers develop more and more terpenes and trichomes. During this period, the temperature ranged between 14 and 25 °C with a humidity level from 50 to 70 %.
54 days into flowering
End of flushing and harvest (9th and 10th weeks)
During the end of the flowering satge, when plants come to the end of their life cycle, we will use only water – without fertilisers – to perform a more rigorous root flushing. The chlorophyll breaks down and the plants lose their green colour: if carotenoids predominate, the plant will turn into yellow colors, but if the anthocyanins dominate – a natural pigment present in blue varieties which appears due to low temperatures as a protection from the cold) the marijuana plants will turn into a beautiful purple/bluish colour.
9th week into flowering
During this period it?s also important to be patient and to observe the resin glands on the buds, waiting for the ideal moment to harvest our plants. Normally, we will harvest them when most the resin glands are white/milky and only few amber trichomes are present, a sign that THC is starting to degrade into CBN, a cannabinoid which has only 10% of the psychoactive effect of THC.
The temperature ranged from 14 to 25 °C and the humidity from 50 to 70 %. The smell of the plants is amazing, constantly producing the aromatic terpenes typical of cannabis plants.
70 days into flowering, plants are ready to harvest
Drying and curing cannabis buds
During the harvest, each plant was carefully examined looking for molds. Fortunately, and despite having a relative humidity rather high during the bloom phase, any plant was attacked by fungi. A good ventilation, and the regular use of Trichoderma during the growth stage greatly helped to avoid the risk of mold on the buds, which often start growing in the substrate.
We discovered few male flowers in one of the 818 Headband plants, but they certainly were sterile because we never found any seeded bud.
The drying process was performed in a dark place, with a constant temperature of approximately 15 °C and during 4 weeks. A long drying process demands more patience, but surely rewards the grower with superior organoleptic quality.
Harvested Cannabis buds, Conspiracy Kush and 818 Headband
The small leaves of the buds, completely covered with resin glands, were trimmed after drying and kept to make high grade homemade hashish. The buds were stored in glass jars and opened every day for 30 minutes during around 3 weeks, until being properly cured; this crucial final stage is called curing.
The grower estimated a yield of 25-30 grams per plant, a total of 250-300 grams.
Smoke report of Conspiracy Kush and 818 Headband
If speaking about the cultivation of these strains, we liked the Conspiracy Kush better than the 818 Headband, mainly due to its beautiful purple colours and impressive production of resin glands, a characteristic trait of all TGA Subcool strains. These are easy to grow genetics, with a relative stability between females, what suggests a great predominance of the mother Obama Kush in this hybrid. The 818 Headband is more vigorous, especially during the stretch stage, developing more side branches and yielding a bit more.
Smoke report of Conspiracy Kush from TGA Subcool:
- Appearance : Great bag appeal, compact buds with a nice layer of resin and beautiful green/purple colours. The small leaves of the buds are covered with resin and produce excellent hashish. Score: 5/5
- Flavour : Conspiracy Kush produces a very soft smoke when inhaling. We will notice hashy and fruity notes – reminiscent of grapes and berries – with lemony undertones. The fruity and sweet flavour increase as the curing process advances. We will see some differences from one female plant to another, but they all have very similar taste. Score: 4/5
- Effect : The effect is mainly body relaxing, typical of Indica marijuana strains, although it isn?t a couch-locking high. This variety is perfect to fight against stress, insomnia or to relax after a hard day of work. Score: 4/5
Smoke report of 818 Headband (Sour Diesel x OG Kush) from The Cali Connection
- Appearance : 818 Headband buds compact, but not as Conspiracy Kush’. The flowers are light coloured and resin production is above average. Score: 4/5
- Flavour : Sour Diesel notes mixed with earthy undertones inherited from the OG Kush. The smoke is harsher than Conspiracy Kush, less refined in respect of aromas. Score: 3/5
- Effect : The 818 Headband produces a powerful and balanced effect between high and stoned, starting with a relatively strong cerebral effect that quickly becomes a more relaxing experience. Thus, it is a good choice for those who are seeking a balanced effect, suitable for the day but also before going to sleep, for medicinal purposes or simply to enjoy the plant recreationally. Score: 4/5
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How to grow weed indoors
Growing weed indoors is great because you can grow it any time of year and you’ll have complete control over the plant and what you put into it. Live in an apartment or a small house? Don’t worry, you can grow weed practically anywhere, even if you don’t have a backyard or a lot of extra space.
Benefits of growing weed indoors
Although it’s more resource-intensive than growing outdoors and you will likely have to spend more money on utilities to power equipment, you can control every aspect of your grow environment and what you put in your plant, allowing you to dial in your setup to grow some primo weed.
Unlike outdoor growing, you aren’t tied to the sun and the seasons. You will be providing the entire environment the plants need to grow, including the grow medium—soil, rockwool, etc.—and regulating the amount of water and nutrients they receive, as well as controlling temperature, humidity, and more for them.
You can let your plants get as big as you want, and can control when they flower and when you harvest, and you can start another batch right away or whenever you want. You can grow any time of year, even straight through winter or summer, and you’ll get consistent crops each time.
Privacy and security
Even in legal states, you may want to conceal your crop from judgmental neighbors and definitely from potential thieves. Growing indoors allows you to grow discreetly behind a locked door.
How to set up an indoor grow room
Below is a list of things to consider and equipment you will need to purchase to get started growing marijuana indoors.
You’ll need a dedicated space for your marijuana plants—you won’t be able to move them around. Ideally, the space is next to a window so you can vent air from the grow space outside. Growing weed plants smell! Especially when flowering kicks in, you’ll want to redirect air so your house doesn’t reek of weed.
A lot of people these days buy grow tents for their weed, but they aren’t necessary. You can grow in a closet, tent, cabinet, spare room, or a corner in an unfinished basement. Just keep in mind that you’ll need to tailor your equipment (and plants) to fit the space.
It’s a good idea to start small—the smaller the grow, the less expensive it is to set up. Newbie mistakes will be less costly if you only have a handful of plants. Additionally, most state laws only allow for growing six plants, but some allow up to 12.
When designing your space, you’ll need to take into account room for your plants, as well as space for lights, fans, ducting, and other equipment. You’ll also need space to work on the plants. Cannabis plants can double in size in the early stages of flowering, so make sure you have adequate head space!
Every space is different and there will be a learning curve to growing in yours.
Cannabis, like all plants, prefers certain environmental conditions in order to thrive. Temperature, humidity, light intensity, and airflow are all factors that will need to be monitored and regulated in order to keep cannabis healthy through its different phases.
Although you’ll be controlling the climate inside the grow space, climate outside the grow space will affect your plants. If the environment outside your grow space is very warm or humid, you’ll have issues controlling your grow space. Choose a cool, dry area with ready access to fresh air from outside.
If you’re growing in a cold, wet basement, you might have to run a dehumidifier or heater to stabilize the environment. Conversely, if your space is too hot, you might need to add extra fans or an AC to cool the plants down.
One trick to avoid hot temps is to have the grow lights on during the evening, when it’s cooler outside, and leave the lights off during the day when it’s hot. This may help bring down the temps, but you’ll only be able to work on the plants at nighttime when the lights are on.
Weed plants need different amounts of light during their vegetative and flowering stages. You don’t have to worry about this in an outdoor setting—the sun and the season dictate this—but when growing indoors, you will be controlling it.
Plants need 18 hours of light a day when in the vegetative stage and 12 hours a day when flowering. The reduction in light from 18 to 12 hours a day is what triggers the flowering cycle—when weed plants start to grow buds.
Because the amount of light a plant receives is so important, you’ll need to make your indoor grow space light-tight. Light leaks during dark periods will confuse your plants and can cause them to produce male flowers or revert to a different stage.
Different lights produce different colors of light. Here’s a brief rundown of the most popular types of cannabis grow lights used for indoor growing.
Can you grow weed indoors without grow lights?
Just about all indoor weed growers use grow lights for their plants. Grow lights ensure your weed plants will grow healthy and strong, while maximizing yields.
In theory, as long as a cannabis plant can get at least 6 hours of full sun a day, whether inside next to a window, or outside, you don’t necessarily need a grow light, but pretty much all indoor growers use them.
HID (high-intensity discharge) lights are the industry standard, widely used for their combination of output, efficiency, and value. They cost a bit more than incandescent or fluorescent fixtures, but produce far more light per unit of electricity used. Conversely, they are not as efficient as LED lighting, but they cost much less.
The two main types of HID lamp used for growing are:
- Metal halide (MH) produces light that is blueish-white and is generally used during vegetative growth.
- High pressure sodium (HPS) produces light that is more on the red-orange end of the spectrum and is used during the flowering stage.
In addition to bulbs, HID lighting setups require a ballast and hood/reflector for each light. Some ballasts are designed for use with either MH or HPS lamps, while many newer designs will run both.
If you can’t afford both MH and HPS bulbs, start with HPS as they deliver more light per watt. Magnetic ballasts are cheaper than digital ballasts, but run hotter, are less efficient, and harder on your bulbs. Digital ballasts are generally a better option, but are more expensive. Beware of cheap digital ballasts, as they are often not well shielded and can create electromagnetic interference that will affect radio and WiFi signals.
Unless you’re growing in a large, open space with a lot of ventilation, you’ll need air-cooled reflector hoods to mount your lamps in, as HID bulbs produce a lot of heat. This requires ducting and exhaust fans, which will increase your initial cost but make controlling temperature in your grow room much easier.
Fluorescent grow lights
Fluorescent light fixtures, particularly those using high-output T5 bulbs, are quite popular with small-scale cannabis growers because:
- They tend to be cheaper to set up, as reflector, ballast, and bulbs are included in a single package.
- They don’t require a cooling system since they don’t generate nearly the amount of heat that HID setups do.
The main drawback is fluorescent lights are less efficient, generating about 20-30% less light per watt of electricity used; space is another concern, as it would require approximately 19 four-foot long T5 bulbs to equal the output of a single 600 watt HPS bulb.
LED grow lights
Light emitting diode (LED) technology has been around for a while, and they are getting more efficient all the time. The main drawback to LED grow lights is their cost: well-designed fixtures can cost 10 times what a comparable HID setup would.
But the benefits are great: LEDs last much longer, use far less electricity, create less heat, and the best designs generate a fuller spectrum of light, which can get bigger yields and better quality.
Check out our buying guide on indoor lights for more info.
Plants need fresh air to thrive and carbon dioxide (CO2) is essential to the process of photosynthesis. This means you will need a steady stream of air flowing through your grow room, which will allow you to move hot air out of the space and bring cool air in.
This is easily achieved by placing an exhaust fan near the top of the space to suck out warm air—warm air rises—and adding a port or passive fan on the opposite side of the space near the floor to bring in cool air. A complete air exchange throughout the entire grow space should occur once every minute or so.
Without proper airflow, a grow space can experience rapid changes in humidity or develop pockets of CO2 depletion, neither of which are good for plant growth. CO2 depletion can lead to nutrient lockout, and areas of high humidity are prone to pest infestation, mold, or mildew.
It’s also a good idea to have oscillating fans to provide a constant breeze in your grow room as it will strengthen your plants’ stems, making them stronger and healthier.
Setting up fans
For small spaces or tents, clip-on fans can be attached to structures like walls, corners, or support beams. For larger grow rooms, use medium-sized oscillating fans or big floor models.
Fans should be positioned to provide direct, even airflow throughout the garden. This typically involves using multiple fans that work together or fans that have oscillation capabilities.
There should be a comfortable airflow both above and below the canopy, and fans shouldn’t blow air directly onto plants—this can cause wind burn, which makes leaves recede into a claw-like deformation.
Dehumidifiers and ACs
If your space is too humid, you may need to invest in a dehumidifier—also known as “dehueys.” However, keep in mind that while dehueys will reduce humidity, they typically increase temperature—you may need more fans or an AC when adding a dehumidifier.
Getting the right climate for your plants can be a delicate balance involving multiple pieces of equipment and also lots of electricity. This is part of what makes growing weed indoors more expensive than growing outdoors.
Fans are a must in a grow space to move air around, so buy some of those before an AC unit. If you find that fans aren’t bringing down the temperature enough, then you may want to invest in an AC.
You will definitely want to invest in a timer for your lights. Because the amount of light a plant receives dictates its vegetative or flowering stage, it’s important to give it a consistent amount of light every day, and that’s done with a timer. It’s a good idea to check your timer at least once a week to make sure it’s working properly.
You can also use a timer for your fans, but a thermostat is better—you can set it to a specific temperature, and the fans will turn on when it’s too hot and turn off when it’s too cold.
Most dehumidifiers and ACs have built-in thermostats, but if they don’t, you’ll want to buy an external one.
For growers who have a little extra money to spend and want full control over their indoor garden, environmental controllers will allow you to automate the process. These devices are essential for if you’re away from the garden for a long period of time.
You can connect a controller to fans, dehumidifiers, humidifiers, heaters, or air conditioners, and set thresholds whereby each device will power on and off based on your ideal environmental settings. Some units run autonomously, making changes based on set parameters, while others allow you to control each element via an app on a phone, tablet, or computer.
How to regulate temperature and humidity when growing weed indoors
You’ll need to ensure that temperatures remain within a comfortable range for your plants, between 70-85°F when lights are on and between 58-70°F when off. Some varieties of cannabis—generally indicas—prefer the colder side of the range, while others—typically sativas—are more tolerant of high temperatures.
For the most part, weed prefers these temps at each growth stage for optimal health:
- Seedlings/clones: 75-85°F; ~70% relative humidity
- Vegetative growth: 70-85°F; 40-60% relative humidity
- Flowering: 65-80°F; 40-50% relative humidity
The two factors you need to control to dial in the environment are temperature and humidity.
Inevitably, there will be fluctuations of temperature and humidity in your cannabis garden. These fluctuations can occur both throughout a grow space as well as within pockets inside a given room. They can also occur at different points within a given day or throughout a season as conditions change in the environment outside your grow space.
It can be tricky getting the right balance of temperature and humidity because they affect each other—turning up your dehumidifier will lower the humidity of your grow space, but it will also increase the temperature of the area. This in turn may require you to turn on an AC unit—everything’s connected!
Tools to measure temperature and humidity
Equip yourself with these cheap and easy-to-use tools to take measurements in your indoor cannabis setup:
- Thermometer: A basic one will allow you to measure how warm or cool the environment is inside your garden.
- Hygrometer: This measures humidity, or more specifically, water vapor content in the air.
- Infrared thermometer, or IR thermometer (optional): IR thermometers use a detection device called a thermopile to measure surface temperatures. Although not necessary, these are helpful in finding out leaf temperatures, which will give you an extra layer of knowledge on how to properly regulate environmental conditions.
Controlling temperature in your indoor grow room or cannabis garden can be achieved by manipulating these factors:
- Lights: Different grow lights will give off different heat signatures. Hot lights such MH, HPS, and fluorescents produce much more heat than LEDs. Also, lights can be raised or lowered to change temperature at the canopy level.
- Airflow: You can remove warm air (up high) out of the garden and bring in fresh cool air (down low) with fans and ducting. Fans can also help exchange air throughout your canopy, cooling leaves in the process.
- ACs: You may need to bring in an air conditioner to rapidly cool the overall temperature of your grow space if it’s too hot and fans aren’t enough.
- Heaters: Some gardens may require warm air, especially during times when lights are off and not generating heat.
How cold can weed plants handle?
When temperatures fall below 50°F, it can slow a weed plant’s growth and negatively impact the plant. Colder still and the plant could freeze.
Humidity is the amount of water vapor in the air. Here are some ways to control it in your marijuana grow room:
- Dehumidifiers: Dehueys remove moisture from the air but also increase temperature.
- Airflow: As with regulating temperature, regulating airflow will allow you to move moisture in and out of your grow space and control humidity—simply opening up a space, i.e., opening the door to your grow room or tent, can bring down humidity.
- Humidifiers: A humidifier can add water vapor to a grow space and increases moisture levels if it’s too dry.
- Water: In the absence of a humidifier, you can mist plants with a spray bottle to create extra moisture.
Soil and other media for growing weed indoors
There are many different media to choose from, including good ol’ fashioned pots full of soil, rockwool cubes, a hydroponic tray, and more.
Soil is the most traditional medium for growing marijuana indoors, as well as the most forgiving, making it a good choice for first-time growers. Any high-quality potting soil will work, as long as it doesn’t contain artificial extended release fertilizer—like Miracle Gro—which is unsuitable for growing good cannabis.
Good soil for cannabis relies on a healthy population of mycorrhizae and soil bacteria to facilitate the conversion of organic matter into nutrients that a plant can use. Alternately, you can use a regular soil mix and then supplement your plants with liquid nutrients.
Finding the right soil for cannabis
For most first-time gardeners, we recommend buying a quality potting soil that will provide your plants with enough nutrients to get them through most of their growth cycle without having to add many amendments or liquid nutrients. This pre-fertilized soil—often referred to as “super-soil”—that can grow cannabis plants from start to finish without any added nutrients if used correctly.
You can make this yourself by combining worm castings, bat guano, and other components with a good soil and letting it sit for a few weeks, or it can be purchased pre-made from a local nursery or grow shop.
While shopping for soil, you might be overwhelmed by the options available at your local garden store. The soil type is the basic structure of your soil. From there, look at nutrients, microorganisms, and other amendments that improve the soil. Your choices will be flooded with words like:
- Worm castings
- Bat guano
- Peat moss
- Fish meal
- Bone meal
- Glacier rock dust
- Plant food
These are just some examples of amendments commonly used in different types of soils. Heavily amended soils will have long lists that break down all organic nutrients they contain. Some companies create soils that offer a great structure with base nutrients, but allow you to fill in the gaps as you desire.
Soil temperature for cannabis
Soil should be in the 65-75°F range, or about the temperature of your grow space. If it seems like soil is getting too hot under grow lights, add some water on the cold side next time you water.
What soil temperature is too hot for weed plants?
A soil temperature above 80°F for a plant isn’t ideal. When soil gets that hot it can be difficult for roots to uptake nutrients.
Hydroponics is a system of growing weed without soil. Plant roots are suspended in water, which is constantly recycled throughout the system. One of the main benefits to growing hydro is that roots have easy access to nutrients. Many argue that you can grow bigger, more potent buds with hydroponics.
Can you grow weed indoors without hydroponics?
Hydroponics is an advanced form of growing that experienced growers may take on, but indoor growing can be done with soil and pots for all levels of growing experience, and is much cheaper and easier than dealing with hydroponic systems.
What type of container you use will depend on the grow medium, the system, and the size of your plants.
Inexpensive options include standard plastic pots or cloth bags, while some growers choose to spend more on “smart pots” or “air pots”—containers designed to enhance airflow to the plant’s root zone.
What size pot do I need?
Many growers will start plants in a one-gallon pot and then transplant up to a bigger pot as plants get bigger. A lot of growers will transplant once, from a one-gallon to a five-gallon pot, and harvest from there. If your plants get bigger, they may need a seven- or ten-gallon pot.
What to look for in a pot
Your cannabis wants a safe, healthy place for root development. Without healthy roots, your cannabis will never thrive. Roots are in charge of water retention, nutrient absorption, anchoring the plant, and they also facilitate vegetative growth.
Drainage is key, as cannabis plants can get waterlogged and develop root rot. If you repurpose containers, be sure they have holes in the bottoms and set them in trays.
For a root system to develop and thrive, they will need the following:
- Drainage: Water retention is paramount for healthy plants—without it, your cannabis will wither and die. But too much water will waterlog your plant and lead to root rot, killing roots.
- Oxygen: Plant roots require oxygen to function properly. Choose a container that facilitates enough oxygen for root development without overexposing them to the elements—containers do this though various styles of perforation.
- Nutrients: Roots require optimal conditions for nutrient absorption to occur. This includes pH balance, optimal temperatures, and nutrient availability.
- Space: Roots need plenty of space to branch out. A container that is too small will cause it to become rootbound and choke the plant.
Traditional plastic containers
Standard plastic containers are a popular option for growers operating on a budget. These pots are inexpensive and provide the essentials for your plants.
- Low overhead costs
- Solid drainage (plus it’s easy to add more holes)
- Transplanting is easy and inexpensive
- Can’t protect root systems from temperature fluctuations as well
- Lack of durability which can cause cracks and structural damage over time
- May have airflow issues depending on the grow medium
These are quickly becoming the standard. Roots in fabric pots grow to the outer edges and attempt to bypass the porous fabric wall but are cut back, allowing new growth to occur. This process, called “air pruning,” results in a denser root composition which promotes healthy growth and development.
- Promotes dense, healthy root systems
- Increased airflow to roots
- Excellent drainage
- Require more attention and maintenance because they dry out quickly. Note: You can use larger pots to help slow drying.
- Flimsy structure can make plant support challenging
Terra cotta pots offer a unique set of benefits to growers in hot climates.
- Absorb moisture and retain lower temperatures during hot days
- Heavy weight helps to anchor larger plants
- Less than optimal drainage; drilling holes into clay pots is possible but requires special tools and is labor-intensive
- Heavy weight makes it difficult to transport plants
Caring for your indoor cannabis plants
When starting with clones or seedlings, you’ll want to check your plants every day because they’re delicate and sensitive to environmental conditions. You may need to adjust temperature and humidity levels in your indoor grow space at first to hit the sweet spot for your plants.
As your indoor weed plants grow, they’ll need less attention, but you’ll still need to check up on them every 2-3 days.
Best water for growing weed
The cleaner the water, the better for your plants, but you don’t need to buy a bunch of distilled water. Generally speaking, if you’re only growing a few plants and your tap water is good enough to drink, it’s probably fine for your weed plants.
You can invest in an EC (electrical conductivity) meter, which measures the dissolved salts of your water, to be sure. Plain water should be between 50-300 ppm.
Ideal water temperature for growing weed
Water shouldn’t be too hot or too cold—keep water temperature between 65-75°F. Cold water can shock the plant and make it difficult for roots to absorb. Excessively hot water can damage plants.
When growing weed indoors, you’ll likely have to add nutrients to your plants. You won’t need to add nutrients every time you water, but get on a schedule where you water every other time, or two on, one off.
Before watering, check the pH of your water and add pH Up or Down if needed.
Do weed plants like warm or cold water?
If anything, use water on the cold side, rather than the hot side. Under 65°F will slow nutrient uptake, but water above 75°F can damage a plant.
If using nutrients, estimate how much water you’ll need for all of your weed plants so you can measure out and mix in the appropriate amount of nutrients.
Remember, a common mistake newbie growers make is to overwater plants.
Check out our Guide on nutrients for more info.
Check for pests, mold, or nutrient deficiencies
You’ll also want to take this time to check over your weed plants for pests, mold, or nutrient deficiencies.
Examine the tops and undersides of leaves for pests or discoloration—spider mites live on the underside of leaves—as well as stalks and branches. Also, check the soil for pests.
Make sure all equipment is on, no breakers have flipped, and everything is running smoothly. Check lights, timers, fans, dehueys, ACs, and anything else that plugs into the wall or has a battery.
Think of all the equipment in your grow space as organs in the body—if one fails, the others will have to work a lot harder for a bit, and then will fail in a matter of time.
Daily maintenance checklist for your indoor marijuana grow
- Water plants
- Check pH of water
- Measure and mix nutrients
Indoor marijuana grow timeline
The growth stages of marijuana can be broken down into four primary stages from seed to harvest:
- Germination (3-10 days)
- Seedling (2-3 weeks)
- Vegetative (3-16 weeks)
- Flowering (8-11 weeks)
Generally speaking, it takes anywhere from 10-32 weeks, or about 3-8 months, to smoke what you’ve grown. (It’ll be quicker if you start with a clone or an autoflower seed.)
That’s a big variance, but it really depends on how big you want your plants and how often you want to harvest—you can have multiple harvests of smaller plants, or less harvests of bigger plants.
For example, it takes less time to grow 3′ weed plants than 5′ plants; in the span of a year, you can maybe grow four harvests of 3′ plants, or two harvests of 5′ plants.
You’ll likely yield about the same amount of weed in both cases, but more harvests mean you’ll have fresh weed to smoke more often and have more opportunities to grow different strains. But more harvests also means more work in cleaning up the space between harvests, trimming, etc.
The biggest variability in how long a marijuana plant takes to grow will happen in the vegetative stage—after the seedling phase and before flower.
The flowering stage will always take about eight weeks—some strains take seven, some nine, some even more, it depends on the strain.
So when growing weed indoors, you can control the size of your plants by flipping them into flower whenever you think they’re big enough in the vegetative stage.
Odor control in your indoor marijuana grow
As much fun as growing marijuana indoors is, having a home that perpetually smells like fresh weed can be a serious inconvenience, if not to you than possibly your neighbors. Although weed odor from a small indoor grow in a closet is much easier to manage than a large grow with several flowering plants, both can produce pesky odors that will permeate an entire home if left unattended.
Plants in the vegetative stage maintain a low odor as they haven’t begun to produce terpenes, the plant’s aromatic compounds. As weed plants transition into the flowering phase, trichomes will start to develop and produce terpenes, causing them to smell more.
Here are some ways to mitigate odor when growing weed indoors.
Check temperature and humidity levels
The first step in odor control is making sure temperature and humidity are under control in your grow space—high temperature and humidity will perpetuate odors.
As your plants get bigger and especially when they start flowering, they’ll start to smell more. Outfitting your grow with a dehuey or AC can help bring odor down.
Make sure air is circulating through your garden
Proper air circulation will help maintain temperature and humidity, and also bring down odor. Ideally, air needs to move through a garden every few minutes, and you should create a vent to the outside. Oscillating fans, and intake and exhaust fans can move air through your garden quickly, taking odors out with them.
Odor absorbing gels may help
Odor becomes much more difficult to manage in the final six weeks of a marijuana plant’s life, when trichomes and terpene production ramps up. You can also get odor-absorbing gels, which replace weed smells with other scents. Keep in mind that odor gels don’t eliminate odors, but simply mask them.
Activated carbon filters
These come in different shapes and sizes and are a great way to get rid of odor in an indoor weed grow. Also known as “carbon scrubbers” for their ability to get contaminants out of the air, these employ activated and highly ionized carbon to attract particulates responsible for carrying odor, such as dust, hair, mold spores, and volatile organic compounds, and traps them in a filter.
Carbon filters usually work best when positioned at the highest point in your grow space, where the most heat accumulates.
Patrick Bennett and Trevor Hennings contributed to this article.
Growing Cannabis From Seeds Indoors
Article written by
Dipak Hemraj Head of Research and Education
Dipak Hemraj is a published author, grower, product maker, and Leafwell’s resident cannabis expert. From botany & horticulture to culture and economics, he wishes to help educate the public on why cannabis is medicine (or a “pharmacy in a plant”) and how it can be used to treat a plethora of health problems. Dipak wants to unlock the power of the plant, and see if there are specific cannabinoid-terpene-flavonoid profiles suitable for different conditions.
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