7 Big Indoor Grow Mistakes Rookie Growers Make (and How to Avoid Them)

The most common indoor grow mistakes are not checking pH, overfeeding, overwatering, starting with sketchy genetics, getting the light wrong, telling too many people and harvesting too early. You learn to grow by growing, but knowing these ahead of time will save your first harvest. Reading books and articles on cannabis sites helps, but hands-on experience is always the best teacher.

What do you need for an indoor grow?

In a home indoor grow, the goal is to recreate (and improve on) the natural conditions that let cannabis thrive.

That's why indoors you swap sunlight for grow lights, create airflow with exhaust fans and circulation fans, and so on. The only things indoor and outdoor have in common are the growing medium (if you're using soil), the fertilizers and the seeds.

Before you set up an indoor grow, there are a few things to think about:

• Physical space: where you'll set up your grow cabinet, grow tent or grow room.
• How much you smoke: the amount of weed you usually go through will decide how much growing space you need.
• Budget: obviously, going cheap on your grow will also cap the quantity and quality of your harvest. And starting out with secondhand gear isn't a great idea either, since it can bring problems you'll definitely want to avoid.

If you want to learn more about growing indoors, we've got an indoor grow guide to help you raise your cannabis plants and get the best yield possible.

Now let's get into the home indoor grow mistakes you'll want to avoid if you want a big, healthy plant:

Mistake #1: not checking your pH

When you grow cannabis for the first time, there are a lot of acronyms, formulas and schedules to keep track of. Some growers get overwhelmed and just wing it, watering without checking whether they've got the right soil or the right pH. It's a plant, it needs water like any other, right? Cannabis jargon can definitely be confusing, and you can ignore a lot of it… except pH.

What is pH in cannabis plants?

pH measures how acidic or alkaline a liquid, or a solid dissolved in one, is. Here's why it matters: even when there are plenty of nutrients in the soil, your leaves can show deficiencies if the water reaching the roots has the wrong pH, because the plant can't absorb what's there (this is called nutrient lockout).

The wrong pH at the roots can cause all kinds of leaf discoloration, problems and deficiencies. The problem usually clears up once the plant gets water at the right pH. Managing pH is one of the more technical details almost every grower has to deal with, unless you're lucky enough to have perfect water.

Soil growers aim for a pH of 6 to 7 for the best nutrient uptake. Growers using hydro, coco and other soilless media aim for a pH of 5.5 to 6.5.

Mistake #2: overfeeding nutrients

This one is super easy to make, and almost every grower either will make it or already has. Most nutrient companies print a feeding schedule on the label that recommends doses that are way too high.

Overfeeding an indoor grow, or any grow, leads to something called nutrient burn. In most cases nutrient burn won't kill your plants, but it leaves a mark and can seriously hurt your yield. Brown, crispy leaf tips all over the plant are the telltale sign of nutrient burn, caused by nutrient levels that are too high.

To avoid it, follow the feeding schedule on the label, but start at half the recommended dose.

Mistake #3: overwatering

A lot of us grew up thinking plants need sunlight and water every single day. Add that to a new grower's urge to take care of their babies, and plenty of people end up watering way more than they need to.

Indoors or outdoors, overwatering keeps roots from getting enough oxygen, which makes plants droop. In severe cases, it can kill them.

Overwatering happens when you water too often or give too much water at once.

How do you know when to water?

Water when the soil feels dry when you stick your finger 2 to 3 cm (about 1 in) into it. If you're growing in coco, water every 1 to 2 days. If the coco stays wet for more than 3 days, give less water at a time until the plants get bigger and start drinking more. You don't need to wait for coco to dry out, but don't water if the medium still feels wet 2 to 3 cm down. If the container feels light when you lift it, it's definitely time to water.

Mistake #4: bad genetics

When you find a seed in your bud, the urge to plant it is real. If you've got some grows under your belt, it might turn out great, but if it's your first time, you really want to start with good seeds. Good genetics tell you what kind of yield to expect, what care, temperature and humidity the plant needs, which phenotypes you'll get and so on.

Your best bet is to get quality seeds from a trusted source. If you're going to invest in good lights and nutrients, using a random seed means wasting all that on a plant that could have weak genes or turn out to be the wrong sex.

Mistake #5: too much indoor light (or too little)

Light is everything for plant growth. If you notice your plant stretching, with lots of space between nodes, it's asking for more light. Young plants can get by okay without much light, but the yield will be really poor. A flowering plant that isn't getting enough light will give you airy, weak buds.

With too much light indoors, plants get stressed and become more prone to disease and more vulnerable to pests. So keep an eye on your lamp and make sure it's at the right distance: about 30 cm (12 in) for 600 W lamps, 25 cm (10 in) for 400 W lamps and 40 to 50 cm (16 to 20 in) for 1000 W lamps.

Mistake #6: not keeping your grow private

Even where growing weed is legal, it's smart to keep your indoor grow on the down-low. There's usually zero upside to announcing you're growing cannabis. People often wonder how indoor grows get busted, and the answer is pretty simple: nosy neighbors who don't like your grow (or just don't like you) may call the police, and there's always some thief out there who'll try to rip off your plants, figuring you're unlikely to report it.

Mistake #7: harvesting too early

Growing weed definitely takes patience before you get to enjoy the fruits (or rather, the flowers) of your labor. If you're in a hurry to harvest, go with an autoflower, which can be ready in about 90 days. Harvesting too early cuts your yield, the buds won't look the way they should, and the terpenes won't be at their peak, which means weaker effects and potency on top of a smaller harvest.

Also remember: 10 to 15 days before your expected harvest date, it's common practice to flush the roots (water with plain water only) so plants stop taking up nutrients and you get to taste the flowers clean and at their best.

There are plenty of big mistakes you can make growing weed, but these are some of the most important ones to avoid. Growing indoors solves a lot of problems, but it also brings a few of its own that you need to keep in mind.

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