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How to Grow Autoflower Cannabis Indoors

17 February 2023
Starting your first grow? Fast Buds runs down all you need to know before you start.
17 February 2023
11 min read
How to Grow Autoflower Cannabis Indoors

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  • 1. Light
  • 1. a. Fluorescent
  • 1. b. High-intensity discharge
  • 1. c. Led grow lights
  • 2. Growing medium
  • 3. Nutrients
  • 4. Water
  • 5. Carbon filter
  • 6. The growing process
  • 7. In conclusion

Autoflowering seeds grow, well, automatically when cultivated outdoors. Plant, water, and fertilize them, then let the sun and mother nature do the rest. Indoor growing is more technical, but just a bit. Whereas the Earth and the sun provide abundant soil and light, you'll have to provide those for your plant. You'll also need to pay a bit more attention to plant nutrition, as well as install a carbon filter to keep the smell away unless you're like us and want your home to smell like fresh marijuana all the time. Here's all you need to know to get started growing autoflower weed indoors.

1. Light

With no sun to rely on you'll need to provide light for your plants. There are many different lighting options to choose from, and knowing which one is best for you can be tricky.


Fluorescent lights are cheap, easy to find, and fit nicely in even the most cramped grow environment. They don't generate a significant amount of heat relative to other options and can be kept close to plants without burning them. Compared to other options like HID (see below) fluorescent lights will grow plants of slightly lower yields. The tradeoff here is the grower takes a small impact to their yield but sees massive savings in electricity and heat management. Fluorescent lights come in a few varieties, each with their respective pros and cons.


You've probably seen Compact Fluorescent Light bulbs in your own home. They're easy to find anywhere light bulbs are stored. They're cheap, small, and easy to find, making them perfect for private-minded growers with limited space to grow.


How to grow autoflower cannabis indoors: CFLs

CFLs are fairly cheap but you'll need multiple CFLs per plant.

Unlike other fluorescent bulbs, you'll want to keep CFLs close to your plants to make sure light reaches lower leaves and bud sites.


These long tubular lights often plug into panels of four or five lights and take up significantly more space than CFLs, but they produce a light spectrum slightly better suited for cannabis growth. You can find them at any garden center or home improvement store. When growing seedlings or clones, be sure to keep the light far away. While you can keep T5 lights closer to mature specimens, their light is too intense to stay close to more fragile, younger plants.

High-Intensity Discharge

These large bulbs produce massive amounts of light at the perfect spectrum for growing cannabis, and they're more efficient than fluorescents in terms of weight of bud per watt of power used. That doesn't mean growers will see lower electricity bills using HIDs. Producers using smaller spaces can generate more than enough light using T5s or CFLs at lower wattages than even the most miniature HID bulbs. HID lights generate a lot of heat, and you will have to manage your grow space's temperature when using them. If you don't have a good exhaust system, it's better to stick with a low-heat option like CFLs or LEDs. Like CFLs, HIDs also come in a few varieties.

Metal Halide

Metal Halide lights are usually used during the vegetative phase of growth, but can also be used during flowering. Their bluish light is perfect for vegging plants, and while this will get the job done, many dedicated growers switch to another lighting solution once buds start to form.

High-Pressure Sodium

High-pressure sodium lights serve as counterparts to Metal halide lights. If efficiency is your goal, you can't beat a combo of MH during veg and HPS during flowering. The yellow light produced by HPS enhances bud production.

LED Grow Lights

For the grower looking to cultivate discreetly, or for just their personal use, LEDs are the ideal middle ground between the efficiency of HPS lights and the low power consumption of CFLs. LEDs produce a more favorable spectrum than fluorescent lights, generate less heat and use less power than HPS lights. You can recognize pictures of plants under LED lights through their purple hue. For many years these purple boards of diodes were the only option if you wanted to grow with LEDs.


How to grow autoflower cannabis indoors: LEDs

Nowadays you can find excellent LED grow lights in the $100-200 range.

However, recently, chip-on-board LEDs or COBs have made the lives small growers much easier. If you're only growing a couple of plants at a time, you can't go wrong with COB lights, which produce a much more photogenic white light compared to the harsh purples of traditional LEDs.

Modern LED Light Fixtures

While this was the case a couple of years ago, things move quickly with cannabis cultivation, especially LED technology in the last few years. Unless you are looking to set up a tiny wardrobe grow with CFLs, there is really no reason to use anything other than LED panels as your main grow light option. HID rigs were, for decades, the true gold standard for all in cannabis growing situations - but, the times they are a changin' dudes and dudettes. There are a few key reasons why you should only consider LED panels if you are in the process of setting up an indoor grow room -


  • Once the rich boys of the growing world, in recent years we have seen a huge downswing in the price of LEDs. No longer will you give your accountant (or spouse) a heart attack every time they hear whispers of LED grow lights. Sure, they are still slightly more expensive than HID options in terms of initial costs (good ones, anyway - don't buy a super cheap option, you'll just have to replace them way too quickly)
  • They are much more economical in terms of ongoing costs - LED panels cost about half as much to run per hour, so you can save those pennies for other important things - like terpene-rich buds. And when you think about how many hours those lights will be on each day (18 to 20 for the full run when growing autos), it's easy to see just how quickly those dollars spent will be covered.
  • They run much cooler than HID rigs and they produce a spectrum of light that is ideal for growing cannabis. Not only does this mean that you don't have to worry as much about light burn or heat stress, it just makes setting up the optimal environmental conditions so much easier. One of the hardest things to do with indoor cultivation is to get the temperature to sit in the correct range, especially if you are growing in an area where the ambient temps are higher than this. LEDs make that job 1000 times easier.

If you are looking to grow autoflowering cannabis indoors, then LEDs are pretty much your only option - not all LED lights are created equal though and there are many manufacturers producing panels with sometimes dubious claims and dubious performance. Do your research and read unbiased reviews of the different options available, before making a purchasing decision. Some of the best brands and panels available come from top-name companies like Samsung, Philips, and G8LED. These companies have all invested heavily in creating custom LED solutions that are primarily meant for indoor cannabis cultivation - they offer a variety of wattages, spectrum types, and even specific models that are tailored toward autoflowering strains. These are the kinds of panels you should be aiming to grab.


But, if you are looking for a slightly cheaper option, you're in luck. The rise of the LED era has brought with it a bunch of new companies that are doing good things. Brands like VIVOSUN,  Spider Farmer,  HyhotonFlux, AC Infinity, and MARS HYDRO are all great options. We used to heavily suggest that all new growers stay well away from full kit setups online, and for good reason. But, nowadays some of the bundles offered are actually really great quality and a fraction of the price of picking up everything separately. There is a wide range of options to choose from, but we love these couple for starter kits -


  • VIVOSUN GIY 4x4 Grow Tent Complete System,
  • MARS HYDRO 4x4 Grow Tent Kit Complete System
  • THEBUDGROWER Complete All-in-One Home Grow Solution 48"x48"x80
  • Spider Farmer Grow Tent Kit 4x2 Complete
  • IPOW Grow Tent Kit Complete 3.3x3.3ft LED Grow Light

2. Growing Medium

You've got space, you've got light, but what are you going to plant your seeds in? There are seemingly endless choices for growing mediums, ranging from hydroponics and aeroponics to dollar store gardening soil. We'll tackle hydro and other high-tech mediums in another article, for now, we want to keep things easy for new growers. After removing the high-maintenance, high-tech options, we're left with three choices: soil, soilless, or a combination of the two.


Soil is what millions of years of evolution trained cannabis seeds to grow in, and there's nothing wrong with germinating, planting, and trusting the plant's genetics to take care of the rest. The only caveat we have to add is that you find high-quality soil, either on the internet or at your local hardware store. Cheaper, low-end soil is meant to grow small flowers, not giant cannabis bushes.


How to grow autoflower cannabis indoors: soil

Soil is a great substrate for beginner growers.

In our experiments with bargain brands, we've found that plants grow quite well through the vegetative stage, but once flowering starts our plants quickly exhaust the available nutrients and begin showing signs of malnutrition. This problem can be corrected with the addition of outside nutrients, but it's just easier to buy high-quality soil in the first place.


There are a variety of soilless options to choose from, but the most popular for growing Cannabis is Coco Coir. Made from coconuts, Coco looks like soil at a glance but is ideally suited for growing friendly bacteria that will give your plants nutrients. You don't have to use it by itself; you can also mix it with traditional soil to create an ideal blend.

3. Nutrients

You'll need at least a little bit of fertilizer to get the most out of Fast Buds seeds. Some strains, like our Blue Dream'Matic, require just a bit and are easy to overfeed, while other strains like our Green Crack will take all the nutes you can give it. In general autoflower strains are almost always hungry for calcium and magnesium, so you should get a brand that provides those vital nutrients.


How to grow autoflower cannabis indoors: nutrients

All cannabis plants need nutrients in order to produce big, fat, tasty flowers.

Beyond that, don't stress over it. The growing environment and medium, more than strain, determine what kind of nutrients you need to provide your plants. Since those are unique to each grower, it's hard to give generalized advice.

4. Water

Of course, your plants will need water. A general rule of thumb is to water whenever the soil is dry from the top to two centimeters or an inch down. Depending on your setup you might water once every two days during vegging, but once in-flower Fast Buds' plants will drink and drink. For example, a mid-flower Stardawg in an 11-liter pot can take two liters of water a day without leaking anything through drainage. It drinks it all.

5. Carbon Filter

If you're trying to grow without alerting the neighbors, you'll want a carbon filter to take care of the smell of growing marijuana. Buying a filter and fan might be the most expensive part of your setup, but you'll more than make it up in the peace of mind you get in return.

6. The Growing Process

Ok, so we’ve run over all the vital equipment to grow indoors, but let’s take a very brief look at the process. 


First things first, let’s get those seeds started! You want to fill up a small glass with water and drop the seeds into it and let them sit for 24 to 48 hours. If the seed shells are extra hard, or if you have been holding onto them for a while then you may want to make some small scratches on the outer shells to help that tap root emerge.


How to grow autoflower cannabis indoors: germination

Germination is the first step of a cannabis plant's grow cycle.

Once they have soaked for a day or two, find some unbleached and unfragranced paper towel. Wet it, squeeze the excess water from it place the seed into it, and fold it up into a neat little envelope. Place inside a ziplock bag and check it every day or two to ensure proper moisture levels and to see if the tap root has emerged. Once it has, it’s time to plant.

Planting and Growing

Its always advised planting in the pot you intend to harvest from with autoflowers, as transplanting will stress the plant and cause a pause in growth. Since autos have a predetermined genetic timer for flowering we want to stress them as little as possible to ensure the best growth, so always treat them like the princesses they are. Once planted they go straight into the grow area, and for the best results, we recommend putting them under either an 18/6 or 24/4 light schedule for the entire life cycle.

The jury is still out over whether LED panels have overtaken HID lighting as the gold standard, but that shift is certainly on the way if it hasn’t already happened. Coco-coir is our favorite growing medium, especially if you are new to the game and interested in hydroponics, and is really forgiving for the novice grower. These days pretty much all of the top-end nutrient companies have a line of coco-coir specific nutes and even produce their own pre-dosed bag of coco-coir ready for seedlings.


Once the plants are all ready, it’s time to cut them down and hang them up to dry. This can take anywhere from 6 to 10 days, and you want the temps to be between 65 – 75 degrees Fahrenheit and humidity between 45 – 55 percent in a dark room. Then it’s time to trim it all up and let it cure for about a month. It may seem like an eternity, but trust us when we say the curing process is vital and you will thank us when you finally smoke up!

7. In Conclusion

That's all you need to get started growing indoors. Of course, growing cannabis cup-winning ganja takes a bit more, but a simple setup can net you 1.5 to 2 ounces of high-THC dried bud a month. While your researching be sure to check out our rundown of The Top 5 Best Indoor Autoflower Strains, and don't forget to follow us on Facebook and Instagram to stay up to date on all the latest strains, deals, and giveaways from Fast Buds.