Top Tips for Growing Cannabis Indoors – How to Maximize the Potential of your Indoor Grow

pink and green petaled flower
April 08, 2020

Mistakes are bound to happen and when they do, you should dust yourself down and move on… (and try not to make the same mistake again). We’ve all forgotten to set a timer or missed a watering once or twice… I know someone who managed to completely forget they had started a grow and was surprised to find six plants in his garage, fully toasted, lights still beaming down weeks later… it was a mistake but it sure wasn’t a common one! 

What Should you do and What Should you Avoid When Growing Cannabis Indoors?

“The only real mistake is the one from which we learn nothing.”
― Henry Ford

Common mistakes aren’t a big deal if you know how to handle them. In fact, you could prevent most, if not all, from occurring in the first place. No one is infallible, however, and mistakes do happen. Even experts are prone to the occasional lapse. We have curated a guide to the most common mistakes and how to avoid them, to make your journey smoother and your growing experience more pleasurable.

1. Be Prepared!

Before you pop those seeds you should have a good idea what you are growing, preparing your space and calendar accordingly. A short indica? A tall sativa? Autos? Have you chosen regular or feminized cannabis seeds? How long is the flowering period? How much do you expect your plants to stretch? Have you got enough room? 

You can only fully prepare the grow room when you know the growth characteristics and needs of the strain you are growing. Check your equipment and make sure you have everything needed before starting. Bad preparation can lead to all sorts of issues like plants outgrowing the space, males pollinating the grow, broken equipment, complaints about smell… Careful planning will give you the confidence to succeed and will keep you firmly on the front foot.

2. Buy the Best Seeds Available

Now and again people find cannabis seeds inside their flower and put them aside to grow out. It’s tempting to think you may be on the verge of discovering the next Bruce Banner or Gelato. Unfortunately, reality always gets in the way of a good fantasy. Growing these bagseeds, as they are known, is almost always a waste of time. Without knowing what you are growing you have no way of fully preparing your room. Are you experienced enough to locate and remove males? Do you have unlimited space? Do you want to spend all that time, money and effort on a lottery? 

The smart option is to buy from a reputable seed bank. Do your research. Read a few reviews. A good sign of a trustworthy seed bank is one that stands by their products, offers guaranteed germination and helpful, rather than token customer support.

A good seed bank will stock only high-quality seeds of stabilized, elite strains. They will have both regular and feminized seeds as well as a good range of autos and they will probably be called the Homegrown Cannabis Co.

3. Be Careful with your Nutrients

If you have decided to use veganic or organic nutrients, congratulations! We would ALWAYS recommend these over chemical nutes and fertilizers, but you need to bear this in mind: plants often take more time to respond to natural nutrients than synthetic ones. This can lead to overfeeding, a classic newbie mistake.

Beginners also make the mistake of thinking that more nutes equals more growth. Unfortunately, excessive nutrients do not benefit plants at all, and may even lead to stunted growth and death.

Do not overdo the nutes! Start with 1/4 strength and gradually add more to help the plants adapt. Sometimes, less is more.

4. Keep Your pH Levels in Check

Okay, so you’ve chosen a suitable substrate or potting mix to grow your plants and you have good quality nutrients. What else do you need to bear in mind? 

It won’t matter how good or regular your nutes are if your pH level is off. When the pH level is outside the desired range your plants can’t absorb nutrients as efficiently. To them, it’s like trying to suck thick liquid through a squashed straw. This can lead to deficiencies that slow growth and reduce both quality and yield of the finished plant.

You can avoid this problem by monitoring the pH level of the medium or nutrient solution (in the case of hydroponics), and making adjustments if necessary. Optimal PH for soil is around 6.5, so make sure your inputs are between 6.2 – 6.7. For hydroponics, optimal pH is around 6.2 and for coco it’s closer to 5.8. Anything more than 3 or 4 tenths outside of the optimal range and your plants will struggle.

5. Don’t Overwater your Cannabis Plants!

It doesn’t matter whether you’ve been growing for ten minutes or ten years, we have ALL made the mistake of overwatering. This particular blunder can have primary and secondary consequences. The most immediate issue would be drowned roots that cannot absorb nutrients and oxygen. Secondary problems include things like fungus gnats. These are irritating little bugs that love wet soil and see it as a perfect place to lay their eggs. These eggs then hatch and the larvae chew through the roots and kill your plant. 

Cycling wet to dry is the best way to prevent overwatering issues. You should get used to weight of a wet pot and a dry pot and use this to determine when to feed and water. That said, you should never let the pot FULLY dry out as this will also kill your roots.

6. Optimize the Growing Environment

There are lots of things you can do to optimize growing conditions, but there are few more vital than keeping temperature and humidity levels within optimal parameters.

Sativa plants tend to thrive in warm environments, while Indica strains can tolerate a little more cold. If the grow room is too hot for your plant, the heat stress will cause the leaves to curl. They will grow weak and produce poor yields, with buds lacking in both flavor and potency. If the temperature is too cold, you can expect the same thing.

How do you optimize temperature and humidity? Easy. Use a digital thermometer to monitor the room temperature and an AC unit to adjust. Keep it around 75°F and the plants should grow well.

Humidity shouldn’t stray too far from 60% throughout the vegetative period and early/mid flowering. Towards the end of the flowering period, you can reduce humidity to as low as 40%. Humidifiers and de-humidifiers are the simplest way to maintain optimum levels.

Airflow is also important. Use fans to circulate the air within the tent and an exhaust system to continually fill the room with fresh, CO2-filled air. A stuffy, over-humid tent will see mold, poor growth and very unhappy plants.

7. Let There be Light (but not too much or too little)!

Once the plants have been flipped into flower, the role of your grow lights becomes even more crucial. Swapping your Metal Halide (MH) bulb for a High Pressure Sodium (HPS) is a good idea (unless you are using LEDs to cover all stages) but you need to be mindful of intensity.

At a minimum, use 400 watts per square meter. The HPS bulb should be close but not enough to burn the plants. You can use a thermometer to measure the temperature where the flowers are closest to the lamp. It should not be more than 85°F. This will obviously need to be monitored as the plants continue to gain height.

If the lamp is too far from the bud sites this can hamper growth and quality, meaning lower levels of cannabinoids and terpenes. One way to solve this is by manipulating the bud sites so that they are closer to the lamp, especially the ones from the lower branches. A good way to do this is to use employ a Screen of Green.

8. Don’t Harvest Too Early

The simplest way to know when to harvest is to know the flowering period of your plant. The majority of modern, photoperiod cannabis plants have an eight to ten-week flowering period, irrespective of how far they lean towards indica or sativa. Blueberry HeadBand (hybrid), 3 Kings (sativa-dominant), and Gorilla Glue Lemon (indica dominant) all share the same eight to ten-week flowering period.

Do not assume this to be the case for all strains. There are sativa strains with far longer flowering times and many Fast Versions that will mature much quicker. Northern Lights Fast Version can finish in as little as six weeks.

Once your plants enter the last few weeks of their official flowering period, you can start checking the trichomes with a handheld microscope, colloquially known as miking the trikes. The trichomes, crystal clear for the majority of flowering, will turn first cloudy then amber or brown as the plant reaches full maturity. Whether it’s just eight weeks into flower or the full ten (or even longer), when 5 – 10% of those trichomes have darkened, she’s ready to harvest. 

If you harvest close to 5 – 10%, you will most likely achieve peak THC concentration. As this percentage increases, more of the THC will breakdown into CBN and the high will be more mellow, relaxing and sleepy. Harvest too early and you risk lower THC and smaller yields. Harvest too late and you risk bud rot, self-pollination and harsh, acrid flavors. This is a nail you want to hit right on the head.

9. Hardwired to Self Destruct

All of your planning, thought and preparation is geared to making sure your plants thrive. You can be as careful and organized as you want but if you mess up the wiring or overload a power outlet then it could all be for nothing. Most grow rooms are easy to set up in terms of power, but if you need extra sub panels or things start to get complicated then we strongly advise you hire a professional. While this isn’t a common mistake per se, we felt it worth mentioning. It is one thing to ruin a grow, it’s another thing entirely to burn down a house.

Don’t Worry if you Still Make Mistakes

Even if all the information we have given you is locked-in and understood, we would be very surprised if you made it through your first (or 100th) grow without making a small flub or blunder. The key is to learn and grow, make hindsight the new foresight and never beat yourself up too much. Own your mistakes and use them to your advantage, for there is no better teacher than experience (or Kyle Kushman).