How to Grow Cannabis Outdoors
This article was co-authored by Jamie Corroon, ND, MPH. Dr. Jamie Corroon, ND, MPH is the founder and Medical Director of the Center for Medical Cannabis Education. Dr. Corroon is a licensed Naturopathic Doctor and clinical researcher. In addition to clinical practice, Dr. Corroon advises dietary supplement and cannabis companies regarding science, regulation, and product development. He is well published in the peer-review literature, with recent publications that investigate the clinical and public health implications of the broadening acceptance of cannabis in society. He earned a Masters in Public Health (MPH) in Epidemiology from San Diego State University. He also earned a Doctor of Naturopathic Medicine degree from Bastyr University, subsequently completed two years of residency at the Bastyr Center for Natural Health, and is a former adjunct professor at Bastyr University California.
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Growing marijuana outdoors produces a higher yield, gives your buds a unique flavor, and it’s far less energy-intensive than using indoor grow lights. Outdoor cannabis plants can grow up to 14 feet (4.3 m) tall and produce 4–8 pounds (1.8–3.6 kg) of quality weed per plant–and it’s not rocket science to grow cannabis outdoors. We’ve put together a comprehensive guide to tell you everything you need to know about picking a location, germinating marijuana seeds, and maintaining your crop to get the highest possible cannabis yield.
How to grow weed outdoors: an intro to outdoor cannabis cultivation
Outdoor cultivators take what Mother Nature gives them and turn it into the best possible harvest. Many cannabis consumers prefer marijuana grown outdoors under the full spectrum of natural sunlight. That unique spectrum creates a greater variance of cannabinoids and terpenes than artificial lighting.
Cannabis has been cultivated outdoors for thousands of years, but before you go putting a seedling in the ground, it’s best to know how the process works and how to make the most of Mother Nature’s gifts. You should also have some idea of how to handle those unwanted gifts you’d rather return — pests and weeds.
How to grow marijuana outdoors
To grow cannabis outdoors, the bare minimum required is basic gardening tools, soil, water, and a spot in your backyard that receives ample sunlight.
Using Mother Nature to cultivate cannabis
Cannabis is a hardy plant that has adapted to climates all over the world. From the cool and arid mountains of Afghanistan to the humid regions of Colombia, over time the plant has been forced to adapt its defenses against a host of problems. But cannabis is still susceptible to extreme weather conditions. Whether it is heavy winds breaking branches or excessive rain causing mold, the great outdoors presents challenges to growers that can be mitigated with sufficient planning.
Becoming intimately familiar with your local climate and seasons is one of the most important steps in producing high-quality outdoor marijuana. Before you grow, you’ll need to know the ideal temperature your plants require in order to thrive, the best site, optimal timing of planting and harvesting, and the season’s photoperiod — the amount and intensity of light available through the duration of the growing season.
Some cannabis genetics have adapted to specific climates and are capable of growing more easily in certain conditions than others, so pay very close attention to the cultivars, or strains, that you choose. A little research will go a long way in ensuring you have a successful harvest.
While cultivars may vary, here are some general rules that will be useful no matter which one you choose.
Daytime temperatures between 75 and 85 degrees Fahrenheit (23.9 to 25.4 degrees Celsius) are ideal for cannabis, while temperatures above 88 degrees Fahrenheit (31.1 degrees Celsius) or below 60 degrees Fahrenheit (15.6 degrees Celsius) can delay growth. Cannabis is considered heat-tolerant, but sustained highs and extreme lows will usually lead to complications that could eventually kill your plants.
In the Northern Hemisphere, cannabis can be planted in early to mid-spring and harvested in mid-fall, depending on the cultivar. In the Southern Hemisphere, the growing season will be reversed with planting in early to mid-fall and harvesting in the middle of spring.
During the first half of the season, the daytime period increases until the summer solstice, which occurs in the Northern Hemisphere on or around June 21 and in the Southern Hemisphere on or around December 21. While the daylight hours increase, the plant’s vegetative stage takes place. During vegetation, the plant will develop the roots and stems that will serve as the foundation for growth until flowering.
After the solstice, the available daylight hours decrease, allowing the plant to naturally transition into the flowering period. Cannabis is a short-day plant, meaning it will begin to flower as the nights get longer and the hours of sunlight decrease.
Most cultivars will begin to flower once they receive fewer than 15 hours of sunlight per day. The latitude of your garden has a direct impact on how many hours a day your plants receive light.
Plan to put plants in the ground based on the temperature, season, and light where you live so your cannabis plants have time to finish flowering before cold, rainy weather sets in.
Choosing the best site for outdoor cannabis
Determining the optimum location is another important factor that can affect the yield and quality of your plants. Cultivators in the Northern Hemisphere should attempt to place their plants in an area with southern exposure to ensure their plants are getting the most available sunlight. The opposite is true for the Southern Hemisphere.
When possible, use natural structures and formations in your garden as windbreaks to prevent excessive stress on your plants that could lead to branches breaking.
If you live in a climate with exceptionally hot and sunny days, use shade cloth to prevent your plants from overheating. In cold areas, natural enclosures and cement or brick walls can be used to help retain any available heat and keep your plants warm.
Depending on your location, you may need to plan for rain. In most regions, the rainy season is typically aligned with the end of the flowering stage and the start of the harvesting period, but this may not always be the case. Rain can be detrimental to an outdoor flowering crop so being prepared to cover or move plants can help ensure a successful harvest. If it does rain on your plants, make sure to immediately shake off any excess water, as lingering moisture can lead to the formation of mold and nobody likes moldy weed.
Planning your garden
Seeds vs. clones
Deciding whether to start with seeds or clones will change the timing and manner by which your plants are introduced to the outdoors.
Plants grown from seeds are typically heartier and more vigorous than clones, as they produce a sturdier taproot that clones are not able to replicate. The vigor that comes from deep roots can be an advantage when dealing with harsh environmental conditions and pest pressures. The disadvantages of growing seeds are the additional attention required to germinate the seeds, the necessity to eliminate any males before they pollinate the females, and the high variability in growth characteristics that results from their genes.
Plants grown from seeds are typically heartier and more vigorous than clones, as they produce a sturdier taproot that clones are not able to replicate. Photo by: Gina Coleman/Weedmaps
If you decide to use seeds, make sure you start them about a month before you would typically start clones to give them time to germinate and adequately develop their taproot.
There are also many advantages and disadvantages of using clones. They can often be found at your local dispensary, are from a proven genetic lineage, and typically do well outdoors, making them the perfect choice for inexperienced growers. On the other hand, clones develop a fibrous root system, as opposed to the deep taproots that seeds develop. Fibrous root systems can reduce the plant’s ability to deal with environmental stress and predatory insects.
Whether using seeds or clones, many cultivators start growing their plants indoors to ensure they are not exposed to damaging weather conditions as they develop their initial root system. The plants can be transitioned outdoors when the weather and light conditions are ideal. Extending the indoor vegetative growth period can help increase yields and allow growers time to select the best plants to be moved outdoors.
Quality soil should be dark, rich in nutrients, and have a light and fluffy texture. The structure of your soil should be capable of retaining water but also allow for drainage of any excess. Organic potting soil blends from your local garden center will do just fine, but more advanced growers prefer to blend their own organic super soil from scratch. The soil itself should be slightly acidic with a pH of around 6. This can be tested with a soil pH meter or test kit.
Container gardens can be convenient as they can be moved around the garden to maximize sunlight or protect them from harsh conditions Photo by: Gina Coleman/Weedmaps
Containers vs. in-ground
Container gardens can be convenient as plants can be moved around the garden to maximize sunlight or protect them from harsh conditions such as rain, heavy winds, or extreme temperatures.
Avoid clay pots as they can be costly, heavy, and retain heat that could dry out the plant’s soil and roots. Fabric pots are the least expensive and most effective solution, as they allow for ample drainage and plenty of oxygen to get to the roots. Plastic containers are also light and inexpensive but tend to retain more heat than fabric pots. Flowering plants need a container that is at least 5 gallons (18.9 liters) to prevent them from outgrowing their containers and becoming rootbound.
Planting directly into the ground or a raised bed requires a bit more preparation but has its benefits as well. Without a container to restrict growth, roots can grow deep and thick to support a strong plant. The added surface area also allows the plant to access a greater quantity of nutrients and water in the soil, compared with a container garden. The major downside is that the plants cannot be moved and could require additional structures to protect them in the case of extreme weather.
Cannabis requires more nutrients than many of the other plants you may have in your garden. Quality soil contains enough organic nutrients to start the growth cycle, but as your cannabis plant grows and transitions into flowering, it may deplete the available nutrients and require additional fertilizers.
The three primary nutrients required for cultivating marijuana are nitrogen, phosphorus, and potassium.
During the vegetative phase, plants need more nitrogen in order to create the roots and leaves that serve as the base for flowering. During the start of the flowering cycle, the plants will require more phosphorus and potassium than nitrogen. Towards the end of the flowering cycle, once the majority of the nitrogen has been depleted, the plants will focus their attention on using the remaining nutrients. The lack of nitrogen is largely responsible for the vibrant purple and orange hues that can be seen on large fan leaves and throughout the plants’ colas.
Avoid all-in-one fertilizers as they can be too high in nitrogen for the flowering cycle and damage any beneficial microorganisms that may be present in the soil. Instead, choose a line of nutrients created specifically for cannabis, and use its suggested feeding charts to avoid over- or under-feeding. Organic sources of nutrients are best, as they are a great source of beneficial microbes, but they may take longer to break down and become available to the plant. Both types of nutrients can be found in dry, pre-blended powders or liquid emulsions, but can also be made from scratch with the right ingredients. Organic compost tea, which includes nutrient-rich ingredients, like molasses and earthworm casting compost, is a popular homemade brew for cannabis farmers.
Organic sources of nutrients include alfalfa meal, bone meal, kelp meal, bat guano, fish emulsion, dolomite, and earthworm castings. Each contains different ratios of nutrients that can be used for different phases of the plants’ growth cycle.
The amount of water a plant needs largely depends on its size, the size of its container, the soil type, and general environmental conditions such as the weather and the intensity of the sun. Larger plants in warmer environments tend to use more water than smaller plants in cooler weather. The amount of water needed will change throughout a plant’s life cycle.
During the vegetative stage, water your plants thoroughly, then not again until the top 1 inch (2.54 centimeters) of soil has dried out. This can be every day or every four days, depending on conditions, but the time between watering will become shorter as the plant grows its roots. Container gardens tend to dry out faster than soil beds, so they’ll need to be watered more frequently.
Wilting plants and dry soil are a direct sign that plants need water. Droopy leaves along with wet soil are a sign of overwatering. Both are common mistakes and can be avoided with some practice.
For a small garden, hand-watering is the easiest, cheapest way to go. It also allows you to get familiar with each cultivar’s needs, and gives each plant the exact amount of water it requires. Irrigation systems can be convenient for a large number of plants or for times when you cannot be in your garden.
Pest and weed control
Pests and wild plants are an inevitable occurrence when cultivating cannabis outdoors. Most issues can be avoided with proper planning. Clearing a buffer area around your plants can go a long way, but your first line of defense is a healthy plant that can defend itself naturally.
Pests come in many forms, from large deer and gophers to small slugs and spider mites. Larger animals and pets can be kept out of the garden with fencing, while gopher wire beneath your soil beds can keep rats and gophers from eating the plants’ roots. Weeds will not damage cannabis, but they will compete for the nutrients in the soil and reduce the quality and yield of your crops. A light layer of mulch on top of your soil can prevent weeds from sprouting in the middle of your plants’ cycle.
Avoid spraying synthetic insecticides on your cannabis plants as further research is needed to determine the health effects of smoking plants treated with synthetic chemicals. Organic pesticide and insecticide solutions can be effective if used properly. If you can avoid it, it is always best to not spray anything on your plants while they are flowering.
Beneficial insects, fungi, and bacteria can also be used to protect your plants from their parasitic or predatory counterparts. Jumping spiders, ladybugs, and other native, beneficial predatory insects can clear your crop of insects such as aphids and whiteflies. When sourcing beneficial insects, fungi, or bacteria, it’s important to research those which are native to your region.
Even if it is legal to grow cannabis outdoors where you live, you should still take some precautions to hide the plants from public view. And it’s often required by law. You can grow your cannabis plants among other plants in your garden to hide them in plain sight. Cannabis can easily grow taller than your average fence, though. Training techniques can help keep your plants shorter. The fewer people who know you are growing cannabis, the better. The ideal situation is to have your grow tucked away on a piece of land where your plants can truly flourish away from prying eyes and nosy neighbors.
Greenhouses can be a great middle ground between the complexities of an indoor setup and the uncertainty of growing outdoors. They provide ample protection from the elements and use far fewer resources than an indoor grow. Greenhouses can be more costly than an outdoor garden and require more planning, but they also allow you to extend the growing season considerably.
Greenhouses also offer growers the ability to harvest more than once per year, if they are equipped with a light deprivation system. These systems allow growers to control the hours of sunlight their plants receive, much like turning lights on and off in an indoor garden, by covering the greenhouse with a black tarp that deprives the plants of sunlight.
Greenhouse structures range from inexpensive polyvinyl chloride (PVC) tubes, often called “hoop houses,” to highly engineered, fully automated, and purpose-built steel greenhouses. Due to their efficiency, greenhouses are quickly becoming the preferred growing method for many large-scale cultivators.
Final thoughts on successfully growing cannabis outdoors
Keep this info in mind as you embark on your cannabis-growing adventure. The smallest adjustments can make all the difference — planting a week earlier, a week later, watering less, watering more, etc.
Quality soil is crucial to the success of your crop and one of the few factors that you have control over when growing outdoors.
Timing is key. A short vegetative phase can cause cannabis plants to flower early, while a long vegetative phase can prevent your plants from finishing their flowering cycle if the weather takes a turn for the worse. The Farmer’s Almanac is a reliable source for planning around the seasons and preparing your crop for success.
Practice makes perfect, so always keep a grow journal and make sure to record any mistakes and wins along the way. Maintaining a record can help ensure you will have successful future harvests.