Growing Weed Indoors Step By Step
So you’ve decided to start a new hobby growing cannabis indoors. This can be fun and rewarding, but also challenging, so it’s important to know what you’re getting into before you take the plunge. There’s lots of information out there, so we’ve tried to boil it down to the essentials you need to know.
Know The Law
Before you make a big investment of time or money purchasing equipment like LED grow lights or grow tent kits, know the cultivation laws for your state. Laws vary widely from state to state, and home cultivation may not be permitted where you live. Obviously, if a state has not legalized some form of cannabis (medical or recreational) then you cannot cultivate. If you are cleared to grow check out our Advanced Platinum P600 review for some of our favorite lighting set ups.
For states with legal recreational cannabis, adults over the age of 21 are usually allowed to grow a limited number of mature and immature plants per residency. It’s the same for medical marijuana, and in some states, medical users can grow more plants if deemed necessary by their doctor.
Refer to your state’s medical cannabis regulatory agency, such as California’s Bureau for Medical Cannabis Regulation, for the cultivation rules.
How Cannabis Grows
Before you start this labor of green love, it is important to understand how a cannabis plant grows.
In the germination phase, seeds sprout and roots emerge in as little as 12 hours or up to 8 days. The seed coat will crack open and root will emerge and grow downward. The root anchors itself after a few days and two leaves will then emerge.
Then, the seedling stage begins and lasts for about a month. This is when the plant is most vulnerable, so it is critically important to control the environment (light, heat, humidity, watering) at this stage.
In the vegetative phase, an indoor plant has rapid vertical growth and produces new leaves. The root system greatly expands as well. The plant is in the midst of the vegetative phase when it has seven distinct sets of leaves. This takes about two months.
The pre-flowering phase is called “the stretch” and can take about 10 to 14 days. During this phase, growers switch to a 12 dark/12 light cycle. The plant rapidly develops and can double or even triple in size during this time. The plant develops many more branches.
Finally, the flowering phase arrives. Depending on the strain (indicas, sativas or hybrids) this phase can last 6 to 22 weeks. The sex of the plant is finally revealed in this phase. Male plants produce flowers that look like grape clusters (panicles). Female plants not pollinated with male pollen will produce sticky buds in a last ditch effort to catch any male pollen blowing around in the wind. These sticky resins are the sweet spot because they contain the largest amounts of THC (or other cannabinoids). A fertilized female plant can also produce the sticky resins, but the plant also produces seeds, which takes most of the plant’s energy, so the resins are not plentiful.
Seeds or Plants?
Seeds produce a higher yield, but growth takes longer and there is an increased risk of growing male plants. Clones are faster-growing and are definitely female, but these plants are more prone to pests and disease. Clones are more prevalent for inherited issues like mildew, and seeds have less illness in plants. If you buy a clone, you’ve got to be ready to grow right away, whereas you can wait a while with seeds.
How Many Plants?
The answer to how many plants you should grow is largely driven by state limits on the number of mature (budding) and immature plants you can have. Within those constraints, don’t bite off more than you can chew to begin with. Start small. It will be much easier in the beginning for you to care for a few plants, and it is less expensive too if you eventually decide that growing cannabis is not for you. Be prepared to lose plants to inexperience, overwatering, under watering, pests or disease.
Your space needs to be clean before you start and easy to clean once plants start growing. You probably shouldn’t have any type of cloth like carpeting or curtains because they’re hard to keep clean.
It is imperative that you control your growing environment for conditions like humidity and temperature. Monitor your space before you make it a growing room. What’s it like? Is it cold and dry or warm and humid? Is it easy to let fresh air in through a door or window? The space you choose should be naturally cool and dry with easily accessible fresh air. If it’s not, you’ll have trouble controlling your growing environment down the road.
Temperature needs to be maintained from 70 to 85 degrees F (lights on) and 60 to 70 degrees (lights off). There’s a bit of variability in temperature depending on the strain you’re cultivating. Some strains like indica do better in lower temperatures, while other strains are more heat-tolerant.
It is important to choose climate control and lighting systems that can be automated. You don’t really need anything fancy (or expensive). You really just need a fairly simple 24-hour timer for your light system and a thermostat for your exhaust fan.
During the dark periods for the plant growing cycle, it is crucial that no extraneous light leak in. If it does, it will trick the plants and they’ll start producing male flowers instead of female flowers.
When you do need a light cycle, it’s so important to choose the right one. Light control is the single most important environmental factor in how much you yield and how good that yield is. Look at your budget, and then choose the best lighting system that you can possibly afford. It will definitely pay off in the long run if you make this up-front investment. Here are some lighting systems to consider:
High Intensity Discharge (HID) Grow Lights are the industry standard. They cost a bit more and are not as energy efficient as some of the other options, but they produce more light. Commonly used HID lights are metal halide and high pressure sodium (HPS) lights. Metal halide is used during vegetative growth and produces a white light tinged with blue, and the reddish-orange HPS lights are used during flowering.
Fluorescent grow lights are very popular among hobbyist growers because they’re easier to set up, they don’t produce a lot of heat, and they’re far cheaper. The down side is that they’re grossly inefficient so it requires many more bulbs to equal the lighting that other bulbs can give you.
Light emitting diode (LED) lights have been designed specifically for indoor growers. Many manufacturers offer lighting fixtures and towers that are extremely energy efficient. Different watts for different growing circumstances also apply. LED grow lights come in a variety of different watts. Smaller wattage is used for small grow of a couple plants and for more light coverage consider perhaps, a 1000 watt grow light or more. But all that great technology comes with a price tag. They’re not cheap and can cost 10 times what a HID system can cost. But they do last longer and they use much less electricity and generate much less heat. If you go with this option, do research to make sure you’re buying a quality product.
Induction lamps are also an option. This is an older technology, actually invented by Nikola Tesla, and recently adapted for indoor cannabis growers. These lamps are also referred to as electrodeless fluorescent lamps. They’re more efficient and last longer than fluorescent bulbs, but are not widely available and they don’t come cheap.
Whatever lighting system you choose, just remember that some lighting systems require ballasts and hoods, so you’ll need more room! Furthermore, some of the lights produce a lot of heat, so you’ll need fans and cooling to control the temperature of your room.
You’ll also want a light system that works with a timer. The light/dark cycle needed for growing indoor cannabis is extremely important. During the vegetative growth phase, lights are on nearly round the clock (around 16 to 20 hours per day). During the blooming period, lights are on half the time, a 12 light/12 dark cycle. Lights have to be turned on and off at the same time every day for both of these cycles, otherwise you’ll stress the plants and won’t get the yields you’re expecting.
If your room doesn’t have natural air flow, you may have to artificially create that steady stream of freshness that your new plants need to survive and thrive. The fresh air is needed to counterbalance the copious amounts of carbon dioxide (CO2) that your plants are producing in a closed space. You might have to invest in a system of exhaust fans to move CO2 out and fresh air in. Typically they need to be replaced near the ceiling to remove the warmer air and CO2 that rise to the top. Be sure to buy an exhaust fan big enough to handle the size of your space and robust enough to move out the heat that is going to be generated from all those lights. Because lighting systems vary widely in terms of the heat they produce, it’s best to decide on your lighting system first, then ensure that you have a proper fan. Do some test runs. Set up your lights in the room before you’ve got the plants in. Monitor conditions throughout the day and night. This will help you ensure you’ve got the proper airflow. Here’s a trick that some growers who live in warmer climates do—they run their light cycle at night to keep temperatures and electric bills low. If the pungent smell of blooming cannabis is too strong for you, add a charcoal filter to your fan or room like many hobbyist growers do.
Soil or No Soil, That Is The Question
When you grow indoors, you have lots of choices for the growing medium you want to use. Some growers use the tried-and-true clay pots and soil, while others go techno with a hydroponic tray/rockwool slab system. There are pros and cons to each choice.
Soil of course is the most traditional growing medium of all time! It’s great for indoor cannabis and it’s easier to use for first-time growers. You don’t need any special soil. Just buy any good quality potting soil. But make sure that the potting soil does not contain any fertilizers or extended release artificial stuff. It’s not good for growing cannabis. You can buy potting soil with natural fertilizers, like organic pre-fertilized “super-soil”. You can go start to finish in the growing cycle without having to add anything to the soil. Some people make their own super soil by purchasing regular potting soil, then adding bat guano and worm castings to supersize it. Other growers use regular soil but add liquid nutrients. So take your pick. You just want to make sure you’re growing organically with no artificial chemicals or additives.
You can also ditch the soil and go hydroponic. Lots of indoor growers are starting to use this method. With hydroponics, you’re soilless, but use concentrated feeding solutions instead. Many of these solutions are mineral salt nutrients that the plant roots absorb directly through osmosis. It gives the plant a much quicker nutrient uptake, and that provides a boost in bigger plants and bigger yields. This growing method requires much more maintenance and monitoring because you have to be really precise in the nutrient allocation.
There are lots of commercial soilless medium mixes like coco-coir, vermiculite, expandable clay pebbles and rockwool to choose from.
Whether you use soil or not drives the decision for the growing containers you will use. Growers use flood-and-drain trays, plastic perforated bags, cloth bags, 5 or 10 gallon regular pots or smart pots with enhanced air flow. Whatever you choose, drainage is key. Cannabis plants absolutely cannot be waterlogged.
You’ve chosen the growing medium and the container. Now it’s time to choose the right nutrients. Your goal is very high quality cannabis flowers, and that requires a lot more fertilizer nutrients than most other crops. Cannabis needs both macro-nutrients in large quantities (nitrogen, potassium and phosphorus) as well as micro-nutrients (calcium, magnesium, copper and iron) in smaller quantities.
If you’re using a pre-fertilized soil or super soil, you’re good. If not, you need to add nutrients weekly at least. Luckily you can purchase pre-mixed nutrient mixtures (powder or liquid); they’re concentrated so you just mix with water. You’ll want to buy a standard mixture for both vegetative or flower growth.
More nitrogen is needed during the vegetative phase, and flower growth requires more potassium and phosphorus. These nutrient mixtures are usually sold in two bottle sets: two for vegetative and two for flower phase. Adding nitrogen in the vegetative phase creates a healthy young plant that will grow very fast. For the flowering phase, you decrease nitrogen and increase potassium and phosphorus to help the plant develop dense buds. Bat guano and worm castings are both rich in phosphorus.
Depending on the strain you’re growing, you also may need an additional calcium/magnesium supplement. Mix the first few mixtures at half strength to see how your plants react. Cannabis is finicky and is easily burned by nutrient overdose. In the beginning it is better to underfeed rather than overfeed and risk losing all your plants.
We can’t forget water. Don’t over water. Cannabis plants cannot sit in standing water because they easily develop fungal root diseases. When trying to determine how much to water, factors like room temperature, the soil or medium you used, and the plant size and type of container all matter. It’s better for the plants to be a bit on the dry side; some growers actually wait until the leaves become a bit droopy before watering the plants again.
Watering is more complicated than you might think. Sure, you can use water right out of the tap, but you really need to know your area water first. If your water has a high mineral content, fungus or pathogens, all of these can affect the plant, particularly the root system. Roots are damaged, leading to inability to uptake nutrients. High chlorine content can kill helpful soil microbes.
Lots of growers filter their water to remove all of these harmful agents and most keep a pH meter handy to regularly check the pH of water, soil and nutrient solution. A soil pH of 6 to 7 is perfect for cannabis plants (it’s about 5.5 to 6.5 for hydroponics) If the pH falls outside of this range, your plants won’t be able to properly absorb the nutrients they need.
Pruning and Training
Cannabis buds form where a leaf branches off at a node of the main plant stalk. The larger the plant, the more nodes the plant has, but more nodes don’t translate to more buds or even larger buds. Nodes higher on the plant will bud and flower; lower nodes won’t because they can’t get sufficient light.
Most growers will prune away any of the plant parts that can’t get good light. Basically the plant is trimmed into a lollipop shape so all the good buds are at the top.
Another tactic growers use is called training. A natural cannabis plant grows one main stalk, but with a little work, you can train the smaller stalks to grow in a menorah shape to assure even light to all stalks and higher yield.
You of course, will need a decent bud trimming machine once all is said and done to create your final product. For small grows we recommend the Spinpro Trimmer. This little guy makes quick work of trimming and does a quality job. Just be sure to replace your blades after a dozen bud harvests.
Go Forth and Grow
Just remember that cannabis is one of the oldest outdoor crops in human existence—it’s been grown in the great outdoors for centuries. Indoor cannabis cultivation is relatively new and has been around less than 100 years. It can be tricky. There are fairly big differences between cannabis grown outdoors and indoors. These are important for you to know as a grower hobbyist, but are also important to know when you buy products from a dispensary.
Perhaps the biggest difference is that indoor cannabis is grown in a controlled environment instead of a natural one. Controlling all of the important growing elements like humidity, temperature, light and CO2 can be very challenging, but if done right, can mean optimized growth and a quality product. Most expert indoor growers find that indoor flowers are in better and healthier condition and that they have higher THC content. We do recommend LED grow lights such as the Platinum LED series as well as offering up some spectacular Viparspectra Reviews.
On the other hand, you just can’t mimic or replicate optimum outdoor conditions, no matter how hard you try, so indoor plants are a little punier and usually have smaller yields.
You can have the greatest of indoor environments, but it is still very difficult to provide the same climate that an outdoor sunny, warm, low humidity outdoor environment can.
Along with outdoor cannabis crop growth comes a whole ecosystem of natural predators like ants, wasps and ladybugs that protect the plants against harmful mites and other insects. This ecosystem cannot be replicated indoors. Mites do often appear indoors and are hard to control if they do.
And then there’s price. Over time, indoor cultivation can cost a small fortune compared to outdoor growing. The indoor climate control equipment and maintenance can really add up over time. As a hobbyist, you’re probably going to do everything yourself, but if you’re thinking of having a large indoor growing area, indoor labor costs a whole lot more because there is a lot more maintenance involved. With indoor plants, you’ll have to constantly water, feed, prune and trellis the plants, and that doesn’t even include harvesting. Conversely, outdoor farming is a one crop, one season venture, so labor is seasonal rather than year-round.