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Learning How to Grow Cannabis with a Master Cultivator

Harry Resin is a world-renowned cannabis breeder and cultivator with figurative roots in Amsterdam
Photos Gracie Malley for Cannabis Now


Learning How to Grow Cannabis with a Master Cultivator

Harry Resin is a world-renowned cannabis breeder and cultivator with figurative roots in Amsterdam —  where he perfected his craft and made his name — and literal roots at his current grow in San Francisco, California, where Cannabis Now visited him for a lesson in growing the greatest ganja.

Harry Resin assures me this will be the “Aha! moment” as we descend the stairs back into the grow room. The longtime Amsterdam breeder who decamped to California has offered to provide a treasure trove of grow tips for my first attempt at indoor cultivation. Today’s lesson will establish the basic building blocks to get started on an indoor cultivation project.

Inside the grow room, Harry has me put on a glove and pick up a pot to understand the amount of moisture the plant is able to take on – in doing so we notice that, despite his team’s best efforts, one plant hasn’t been watered. I can tell this from its weight as I pick it up.

“You get into the habit of picking up pots,” Harry says, offering sage advice for a proper start to growing the world’s most favored flower. “Feel your plants.”

Keep It Simple

Cannabis is an annual plant that is dioecious, meaning it produces both male and female varieties and sometimes also expresses itself as a single hermaphroditic plant representing both sexes. The flowering female marijuana plant creates the resinous buds and the male plant creates flowers that excrete pollen.

To grow marijuana, you can start from either a seed or a clone, which is a clipping acquired from a female ‘mother’ plant. Harry says newcomers should start with a clone, rather than from a seed. He explains even with seeds that are “feminized,” the likelihood of them transforming from female to male is high. When growing from seed one is also responsible for identifying the sex of the plant once its gender traits begin to emerge.

In order to ensure you have a female plant, purchase a clone and have it tested. In this day and age, testing a plant for pesticides (Harry utilizes a detailed list released by the state of Oregon) is absolutely essential towards ensuring good medicine.

For our experimental purposes, we’re not looking for an extreme yield, but rather for quality buds. In this regard we’re exploring a simple set up: one room or grow tent, one light and one plant.

“What’s the goal of growing for yourself? It’s to grow good weed,” Harry says.

Grow Room Design

When setting up the space where you are going to grow it’s essential to have good ventilation: making sure you can bring in cool fresh air and exhaust out hot air is very important. It’s easier to do this by having a room with a window and purchasing filters and fans, rather than dropping the cash on something like a new AC unit. Either way, your grow room should be in a cool part of your house.

An easy, but more expensive fix, for preparing your own grow room is investing in a grow tent.

Resin says an added bonus of a simple set up involves less chance of a slip-up.

“The less mechanical error the less things can go wrong,” he says.

One of the keys to growing great cannabis is controlling the humidity and temperature within your space.

Harry says that this is akin to weather reports accounting for wind versus pressure — the wind blows because of a difference in high and low pressures.

“The pressure you will get from using the exhaust and intake fans in the tent is much better than just wind blowing around from circulation fans as the pressure, more so than the wind, will help the plant to breathe better,” Harry says.

For indoor growing, at least at an advanced stage like Harry as a cannabis breeder is in, controlling pressure is a important factor for an optimal grow.

“You adjust the environment in the room so that it is at the right temperature and humidity for the right cycle while the plant is growing,” he says. “You definitely want to use a filter if smell is an issue.”

At the beginning of growth (or the vegetative or ‘veg’ stage) cannabis plants need a higher humidity and higher room temperature, but at the end of their life cycle (the flowering stage that produces resinous buds) they need a lower humidity and room temperature.

This lower temp in flowering, Harry explains, preserves the aromatic profile of the bud (the terpenes) and allows the medium you are growing the plant in to dry quicker. Like a body builder, its in these final stages that the plant is fed more big protein-based meals to bulk it up.

Harry Resin is a world-renowned cannabis breeder and cultivator with figurative roots in Amsterdam

Get Your Supplies Together


Your medium essentially means your soil, except when it comes to growing cannabis you’re not always going to be growing in soil. The medium Harry uses, cocoa, is a more advanced medium in that it’s less forgiving than others. For beginning growers, Harry recommends Promix or FoxFarm.


Your plant will need nutrients to achieve its full potential. Harry recommends Iguana Juice, Grow and Bloom and Nirvana.

“With these nutrients you’ll achieve a heartier, earthier flavor with your flowers,” he says.

To monitor the nutrient levels on your plants you’ll also need an electric conductivity meter, more commonly known as an EC meter, as well as a pH tester.


Harry can’t say enough about the 1,000-watt double-ended lights from Gavita. In his grow room these lights grow large, stackable nugs. For a smaller grow, Harry recommends 600-watt version, which eliminates the need for an AC.

If you’re going for more than one plant, you may also want to invest in a ballast so the light can move around the space.


For Harry’s commercial operation, which supplies unique premium cannabis though URB delivery, he uses 2-gallon pots. For newcomers, he recommends a 5-gallon Smart Pot. Cloth pots are best for flushing out the added nutrients when your plant is ready for harvesting.


To ensure your plant will flower it will need to be on 12 hours of light and 12 hours of darkness.

“You want it to be roughly the same time every day,” Harry says.

Ensure this is the case by investing in a timer.

Pest Management

To prepare for pests in the grow, you’ll need a few more items. Harry recommends 3-in1 Garden from Organocide along with neem oil. You’ll also need a basic sprayer.

TELL US, have you tried growing your own cannabis?

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