The Budding Botanist: what do you need to grow cannabis?

cannabis growing under lights what do you need to grow cannabis

With more states legalizing cannabis, interest in cultivating the plant continues to rise. And while cannabis may grow like a weed, it takes time, care, and consideration to craft top-shelf buds.

GreenState knows that people have lots of questions about growing cannabis. To help take the guesswork out, professional cultivator Kurt Kinneman, owner of Kinnektion Farms and horticultural engineer at AI Grow, is here to answer your budding queries. From seed to smoke, GreenState has you covered.

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Question: What do you need to grow cannabis?

Water, light, air, substrate, and nutrients. These are the five essential things that are required for you to start growing cannabis at home. Liebig’s Law of the Minimum states that “when several factors are involved in the development of an organism, and one is available in only small quantities, that single factor will determine the organisms’ success or failure.” 

This means that just like any other plant, cannabis is constrained by whatever resource is in the least abundance, and it is up to us as the growers to make sure the plant has enough of what it needs from the beginning of its life cycle until the time the female cannabis flower reaches its peak maturity.  

what do you need to grow cannabis plant in tent
Cannabis plants grow in an indoor tent. Photo: Martin Deja / Getty

Water – the building blocks of life

Water provides your plants with life. It can carry nutrients and supply your plants with everything they need to thrive.  It can also carry bacteria and other elements that can make it difficult for your plants to grow. 

Many people in cannabis use reverse osmosis water, meaning the water has been processed to remove any bacteria and elements, leaving pure H20. This is not a necessity and, in most cases, can be a detriment to your grow unless you know exactly what elements to add back into the water to help your plant flourish. 

It is important to know your water’s pH (potential of hydrogen). Your pH directly impacts an element’s solubility and how your plants can uptake them. Another thing to be aware of is if your water contains any heavy metals like lead, mercury, cadmium, or arsenic. Since cannabis is an accumulator plant, which means it uptakes everything, these heavy metals can become concentrated in the plant’s flowers, which means they will end up in your finished product—and you. Know your water before you start growing!

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Lighting 101

what do you need to grow cannabis lights
Canabis grows indoor under LED lights. Photo: Cappi Thompson / Getty

Light can come from many different sources. The sun, LEDs, high-pressure sodium bulbs, or metal halide bulbs can all provide the required light that cannabis needs. During the vegetative phase, plants require around 18 hours of light daily. During this phase, plants also prefer light that is in the blue spectrum, which is around 400 nanometers (nm) on the light scale. 

When the light is reduced to 12 hours a day, either by the natural change in season or by human interaction, plants begin to flower. During the flower phase, plants prefer a redder spectrum in the 600 nm range. Besides the duration of light and color, intensity is also an important factor to consider. 

The light intensity can be measured in several different ways using various sensors and meters. Most people in the horticulture world use photosynthetic active radiation, or PAR, to measure the amount of light that is getting to the plant. For people without high-tech sensors, it’s important to follow the light manufacturer’s guidance on intensity and recommended hanging distance from the canopy.

Environment matters

Plants breathe in carbon dioxide (CO2) and breathe out oxygen (O2). The humidity and temperature affect the rate at which they breathe. Plants can grow well in ambient CO2, but you can push them even further with increased levels. The humidity and temperature measurements are used to determine vapor pressure deficit (VPD), which can help give you a picture of how your plants breathe. 

When you are growing outdoors, you are at the mercy of Mother Nature and whatever she throws at your plants. In a greenhouse, you can help control temperature and humidity to lengthen the growing season and help provide a better climate for your plants to grow and mature. When growing indoors, you can create a specific climate for your plants that provides the optimum environment for your plant in every stage.

Substrates – what you’re growing in

cannabis in soil
Cannabis can be grown in a variety of mediums, including soil. Photo: NIKISH HIRAMAN PHOTOGRAPHY / Getty

Plants grow in many different types of substrates or media. These substrates can be formed into two categories: soil or soilless. Soils are made up of sand, silt, clay, and organic matter and contain air, microorganisms, and water. Cannabis soils should be well-draining and have diverse microbial and mycorrhizal fungal life to break down the soil elements and provide the plant with the nutrients it needs. 

When using a soilless substrate, the media should be inert and void of all life. Soilless substrates can include water, coco coir, perlite, rockwool, and peatmoss. When using a soilless medium, water must carry all the nutrients that a plant needs.

Nutrients to promote plant growth

The most important added nutrients for cannabis growth are nitrogen (N), phosphorus (P), and potassium (K). Plants can be supplied with these nutrients in two ways. 

The first way is by microorganisms and mycorrhizal fungi breaking down organic matter into usable forms of elements for a plant to uptake. This most commonly happens when you are using a soil media: you feed the soil, not the plants. This means that you are providing a home and nutrient source for the bacteria and fungi in the soil so that they can break it down into suitable forms for the roots to uptake. 

The second way is for water to be used as the carrier for elements usable for a plant to uptake. This is most commonly done when growing in a soilless medium, but salt-based fertilizers can also be used with soil, although these fertilizers will kill microbial life if they are not replenished. Salts can come in the form of concentrated bottled nutrients or can be purchased in their raw form. These nutrients will be labeled with their (N-P-K) ratio, the micronutrients they contain at what percentage, and what the elements are derived from will be listed on the packaging.  

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Essential elements are the keys to cannabis success

There are many ways to supply plants with these five essential elements, whether growing in your backyard garden, greenhouse, or in a room or tent in your house. Plants need these things to live, and how you choose to supply them depends on your available resources. It can be as simple as putting a seed in a pot with well-draining soil and in full sun with frequent hand waterings, or you can get as advanced as having a controlled room with automated processes for functions like lighting, irrigation, and environmental controls. Whatever route you decide, just keep these five factors in mind, and you will have a successful grow!

This article was submitted by a guest contributor to GreenState. The author is solely responsible for the content.

Kurt Kinneman is a cannabis cultivator and owner of Kinnektion Farms. He is also a horticultural engineer at AI Grow, a provider of automation solutions for controlled environment agriculture. In addition to cannabis, Kurt also grows pumpkins on his family farm.