7 Mistakes I’ve Made Growing Cannabis (and Tips to Help You Avoid Them)

Growing cannabis is fun and rewarding, but it can be challenging since mistakes are inevitable in the garden. From equipment issues to nutrient deficiencies, I’ve had my fair share of mistakes in my grows. Whether you’re new to growing or just want to feel better about mistakes you’ve made in your grows, I’m sharing 7 of my biggest mistakes growing weed in my indoor garden.

Mistake #1: Improper Grow Space

The plant on the left grew a lot taller than the two plants on the right, causing issues with light penetration for the shorter plants.

When growing cannabis indoors, you have to ensure that your grow space is optimized for that plant to thrive and give you a larger harvest. It’s good to start growing with intentionality and that means starting with a plan for your grow. Depending on which strain you are growing, they may grow very tall and leggy or short and bushy. I made this mistake when I grew four plants in a 5x5 tent and didn’t consider that two of the plants would grow taller and block the light from two shorter plants. The shorter plants received considerably less light and didn’t have as good of a harvest as the taller variety. 

My tip: If you’re planting different strains in the same grow space, check to see if the breeder has notes on whether the plant will be more indica or more sativa leaning, as this will influence how you choose your plants to grow. Some breeders won’t have this information and the best way to figure out what a plant might be would be to look up those parent plants (e.g., Chem D x Headband) and they should give you an idea for what to expect from your seeds. Ensuring your plants have adequate light for all the flower sites will get you a bigger, better harvest.

Mistake #2: Light Leaks

When growing photoperiod plants, your plant will be dependent on specific light cycles. Ideally, you would have 18 hours with lights on and 6 hours with lights off during the vegetative stage and 12 hours with lights on and off during the flower stage. Because of the plant's sensitivity to light, any small light leak can cause issues with the flowering cycle. I learned this lesson when a dehumidifier I had in my tent had a small LED light that stressed one of my plants and caused it to produce seeds in the flowers (also known as herming). The light went unnoticed for almost 3 weeks before I realized and covered the LED panel on the dehumidifier. When a plant is pollinated, it stops the buds from continuing to mature as the plant goes into seed production, resulting in reduced potency and other favorable effects that you get from the cannabis. 

My tip: Double check your tent during the beginning and end of the dark period in your light cycle to make sure there is zero light inside the tent. Even the smallest bit of light can cause major issues, so cover anything you see that is leaking light through.

Mistake #3: Light Intensity Too Strong

When growing cannabis, using the maximum amount of light you can use isn’t always the best way to get quality cannabis. For LED lights, it is important to keep a distance of at least 12-18” between the top of your cannabis plant and the light during flower. If buds are closer than that, they can suffer from light stress or heat stress, which can reduce the quality of the buds as some terpenes and other beneficial compounds evaporate when exposed to higher temperatures. While growing a Mystery OG plant (pictured above), I didn’t raise the lights with the plant as it stretched during flower, so the buds grew close to the lights. I corrected the issue by raising the lights 18” above the top of the plant canopy and the plant recovered and finished well.

My tip: Always make sure there is a sufficient room between your plant and your grow light. When you make changes to your light intensity, monitor your plants for signs of stress.

Mistake #4: Nutrient Deficiencies

Nutrient deficiencies can happen when you use water with improper pH. In both soil and hydroponic grows, the proper pH in your water allows your plants to use the nutrients you give them. When the pH is past 6, deficiencies can happen easily. In my first few grows with the autopot, I had a really high pH in the autopot reservoir that I didn’t catch until the plants started showing deficiencies. My plant experienced some splotchy brown/yellow spots and some leafs curled downwards as they died. 

My tip: If your plant starts showing signs of nutrient deficiencies, check your pH by testing the runoff of your water if you are top watering. If you’re using an autopot, you should be checking your pH before turning on your autopot reservoir.

Mistake #5: Overdoing Defoliation

Two properly defoliated plants during flower.

Defoliation is when you trim off some of your plant’s foliage to help with even light penetration, better airflow, and more space for your plants to bulk out. This is a necessary step in the flower stage to get the optimal harvest from your plant. When growing some GMO (Chem D x Girl Scout Cookies) plant, I overdid my defoliation and the plant didn’t have enough leaves on it to get to the end of harvest, which resulted in me harvesting earlier than I wanted to. Defoliating too much makes the flowering process much harder on the plant because it reduces the surface area your plant has to photosynthesize, and reduces the number of “energy reserves” you have on your plant.

My tip: When you’re first trying to defoliate, don’t trim off as much as you think you should. You can always go back and trim more later if you need to. I generally don’t touch the top third of the plant and most of the defoliation happens in the lower part of the plant, where there are less likely to be flower sites. 

Mistake #6: Harvesting at the Wrong Time

A combination of improper pH and excessive defoliation resulted in this GMO plant being harvested at 56 days, which was about three weeks too early.

Cannabis, like most plants, has an acceptable range for when you can harvest your crop. Harvesting too early can result in less potency in the final product and an unripe flavor. Harvesting too late can result in a more sedative plant since a good portion of THC has likely converted to CBN during the ripening process. When I first started growing, I wasn’t confident in when exactly to harvest, so it’s been a lot of trial and error. Now, I like to harvest when I see about 20% of the trichomes have turned amber. That tends to give me the best taste and potency in the final buds. 

My tip: Get a feel for your personal harvesting preferences. You can experiment by cutting down a small branch every week around the time of harvest. This is especially important if you’re growing for your own consumption. Learning when the optimal time to harvest is for your favorite strains will help you get a better harvest in the future. 

Mistake #7: Poor Drying Conditions

Drying is a make or break process in growing cannabis. If you don’t dry your flower properly, it is susceptible to mold, which will ruin your entire harvest. After growing out a Chem D plant in my 4x4 tent, I tried drying it in a 2x2 tent, which was way too small for how large the plant was. Ideally, the humidity of your drying area should be below 60%. With the Chem D plant, there was not enough space for an even humidity to settle in the tent. The bud ended up molding after a month in storage since it never had the chance to dry properly.

My tip: Use a big enough grow area and keep your humidity below 60%. You should try to dry your branches in a space that is at least half the size of the space you grew in. You can also add an exhaust fan and/or a circulating fan to your grow area to increase airflow during the two week drying process.