Comparing Indoor Vs Outdoor Cannabis Cultivation in 2023
It’s no secret that cannabis use is increasing. In the past few years there have been changes to legislation in many different countries, making it easier and safer to access weed products than ever before.
One thing that is coming to light though are some of the sustainability issues that exist in the weed industry. There are so many different aspects to sustainability that things can become pretty complicated when it comes to finding solutions too. But there is a lot of history between humans and Cannabis sativa.
This article will look at some of the sustainability issues relating to the cultivation and production of cannabis plants for smokable products. There are a whole set of different considerations when it comes to sustainable consumption, like using rolling papers, dab rigs and roach materials.
However, with the boom of activity, with jobs in the industry increasing, exploration of the potential human benefits of cannabis products, as well as reviews into the many potential uses of hemp products in our everyday lives, it is clear that the cannabis space is going to grow a lot in the coming decade.
How Much Land Area is Dedicated to Cultivating Cannabis Outdoors?
There are different rules and regulations across the globe, which makes it difficult to look into the amount of land area currently used for growing cannabis. However, it’s clear that if humanity starts using more land area to grow smokable crops, it will potentially have less arable land available for food production.
Land-use change has been a big driver of climate change and things like deforestation have been devastating for ecosystems across the planet. We need to be very careful about how we use land moving forward, especially if land is being converted from a natural habitat. This is one of the reasons that more growers are opting for indoor cultivation methods.
What Factors Can Affect Cannabis Cultivation?
The amount of cannabis flower that can be produced on one acre of land varies a lot. There are so many abiotic factors that can impact rates of photosynthesis (a good measure of plant growth rate). For example temperature, light intensity, photoperiod, nutrient and water availability are all environmental influences that influence how quickly a plant grows. There are also genetic elements in each plant, which can change a lot depending on the strain of cannabis that is being grown too.
In addition to the abiotic and biotic factors of the plant and the environment, there is also the skill of the grower to think about too!
Comparing Outdoor and Indoor Cultivation Methods
It does not matter whether crops are grown indoors, outdoors or in greenhouses (which are a bit of both).
Agronomy – the study and science of farming – has a vital role in the cultivation of cannabis. The body of research into plant genetics, soil science, ecology and resource use can all be applied to cannabis cultivation (and rightfully so).
The truth is that the skill of the grower(s) will have the biggest impact on cannabis crops in outdoor and indoor cultivation systems. Agronomic practices can significantly impact the yield, potency, and overall quality of the cannabis crop.
There are aspects of the process that don’t differ, such as pruning and plant training, as well as the drying and curing stages. These will be discussed at the end of this article.
Factors To Consider For Outdoor and Greenhouse Cannabis Cultivation:
Choosing the right location for growing cannabis is critical. For outdoor cultivation, factors such as sunlight, temperature, humidity, and wind should be considered. Cannabis plants require adequate sunlight (at least 5-6 hours of direct sunlight per day) and protection from excessive winds. In greenhouses, climate control systems can help maintain ideal growing conditions to some extent with supplemental lighting, air conditioning and some temperature control.
Soil/ Growing Medium
Cannabis plants prefer well-draining, nutrient-rich soil with a pH between 6.0 and 7.0. Proper soil preparation and amendment are crucial for successful cultivation. This may include adding organic matter like compost, peat moss, or aged manure to improve soil structure and fertility. Soil quality can greatly influence the growth of cannabis plants, so it is important to have a thorough soil test and analysis to ensure the ideal soil conditions for growth.
Soil ecology is also very important when it comes to soil cultivation. There are invertebrates, bacteria, mycelium and a whole host of microorganisms that contribute to soil quality and plant growth. Healthy soils are critical to successful growing.
Proper plant spacing is really important for growers to get the most yield for their land area. However the distribution of plants also impacts quality too! It is essential to make sure there is adequate airflow and light penetration as this will reduce the risk of mould and pests, and cut down on photomorphogenic changes that can arise in crowded settings.
Ideally plants need to be spaced out optimally, but the spacing varies depending on the strain and growth habit. In greenhouses, growers may use trellising systems, nets and plant training to maximise space utilisation and improve light distribution, but plant training tends to be utilised more in indoor growing (more on this later).
Irrigation and water management
Cannabis plants use quite a lot of water and need a consistent supply throughout their growth cycles. Growers need to monitor soil moisture levels and provide supplemental irrigation as needed. It is possible to let nature do the work, but irrigation systems can be highly effective in both outdoor and greenhouse cultivation. It is possible to use different strategies to improve water use efficiency. Things like drip irrigators can deliver water directly to the root zone, thus reducing evaporation from the surface. Growers can also use agronomic practices like partial rootzone drying to enhance plant water use too.
Cannabis plants require essential macronutrients like nitrogen, phosphorus, and potassium, as well as micronutrients like calcium, magnesium, and iron. The soil needs to be regularly monitored so that the nutrient levels can be optimised for the different growth stages. For example, during flowering growth stages, it is usually beneficial to provide supplemental fertilisation as needed, using either organic or synthetic fertilisers.
In greenhouses, hydroponic or aeroponic systems can be used to deliver nutrients directly to the roots, enabling precise control over nutrient availability. However, these methods are better suited to indoor, controlled environment cultivation.
Pest and disease management
Monitoring and controlling pests and diseases is vital for maintaining a healthy cannabis crop. Integrated Pest Management (IPM) strategies can be used to reduce crop losses to pest and disease. IPM can include a combination of biological, abiotic and chemical control methods. Examples of IPM practices include crop rotation, introducing beneficial insects, and using targeted, low-toxicity pesticides.
Horticultural plastics can attenuate the light environment in greenhouses. This is being used to manipulate pest behaviour and reduce the amount of damage that things like aphids can cause to cannabis crops.
Factors To Consider for Indoor/ Controlled Environment Cannabis Cultivation:
Controlled environment and indoor cultivation is touted as the future for a wide range of crops, not just cannabis.
Indoor grow rooms provide growers with the ability to optimise growing conditions and get consistent environmental parameters for light intensity, photoperiod, temperature, relative humidity and even CO2 concentrations. It is generally considered to be the best way of ensuring consistent, high-quality cannabis crops.
Of course, many of the agronomic practices for outdoor and greenhouse cultivation apply to indoor cultivation as well. However, there is a lot more control and there are also some specific practices and considerations for growing cannabis indoors:
Since sunlight is not available for indoor cultivation, artificial lighting is used to drive photosynthesis. There are a range of different types of grow lights used, such as conventional High Pressure Sodium (HPS) as well as High-Intensity Discharge (HID) lamps and Ceramic Metal Halide (CMH) lamps. Each of these types of light uses similar technology and performs similar functions, just with slightly different light quality.
The most impactful development in recent years has been the Light Emitting Diode (LED). LED fixtures can provide enhanced illumination environments. Spectral modification allows growers to manipulate the light spectrums from LEDs. This means the light can emit more or less light in specific wavelengths of light. UV-A, UV-B, Infrared and Far Red wavelengths are crucial for plant growth and development. This is why light modification is such a big thing in the indoor growing community.
LEDs also use a lot less power than conventional light fixtures, so there is potential for much more flower production with less energy consumption.
Maintaining ideal temperature, humidity, and airflow is critical for healthy plant growth. Indoor growers can use a combination of heaters, air conditioners, dehumidifiers, and fans to control these factors. The ideal temperature for cannabis cultivation is generally between 70-85°F (21-29°C) during the day and slightly cooler at night. Relative humidity should be maintained between 40-60%, with lower humidity levels during the flowering stage to prevent mould growth.
There is a lot of research and development in this space at the moment, with growers trying different methods to steer crops and get the most out of their cultivars.
Enriching the growing environment with carbon dioxide (CO2) can improve plant growth and yield. Indoor growers can use CO2 generators, bottled CO2, or mycelium technology to enrich the air around their plants. Ambient CO2 concentrations are around 400-600 ppm in open air. However for cannabis plant growth a target of around 1,000-1,500 ppm is considered optimal.
CO2 supplementation is only really practical in indoor environments. It can reduce vegetation periods and produce bigger plants – and more yields – in less time than plants grown outdoors with no additional CO2.
In indoor cultivation, various different growing media can be used. Soil can be used outdoors, but soilless mediums like coco coir and rockwool are becoming more popular. The reason is because they give a lot of control back to the grower.
Hydroponic systems are becoming more popular too. Plants grown in hydro systems use nutrient-rich water or other inert media, like perlite or expanded clay pellets. Hydroponic systems allow for precise control over nutrient availability and pH levels, which can lead to faster growth and higher yields.
Plants require the same basic building blocks whether they are grown indoors or outdoors. However, the nutrient requirements vary depending on the growth stage and the specific strain, as well as the environmental conditions.
In soilless mediums, growers can use pre-formulated nutrient mixes or create their own custom solutions. This affords a level of control that is not possible in outdoor growing. Furthermore, in hydroponic and semi-hydroponic systems, nutrient solutions are often recirculated, allowing for efficient nutrient use and easier monitoring of pH and nutrient levels. Basically, soilless growing means growers can be precise and deliver what the plant needs, when the plant needs it.
Pest and disease management
Although indoor environments can reduce the risk of pests and diseases, proper monitoring and management are still essential. Integrated Pest Management (IPM) strategies can be used with more precision in indoor cultivation.
IPM strategies can include a combination of abiotic, biological and chemical control methods. For example, predatory species used to manage pest outbreaks with reduced risk of becoming invasive species. There are also things like ozone generators that can kill all microbial life that can cause things like powdery mildew and bud rot.
Indoor growers each have their own methods of growing, which can influence the number of plants they have in a given space. Some indoor growers will have more smaller plants. Others will have fewer larger plants. It all depends on the space and their growing style. Either way, indoor growers can use a range of different plant training techniques to get the most out of each square metre.
What Features Are Consistent For Outdoor and Indoor Cannabis Growing?
Selecting The Right Cultivar
Different strains have different preferences when it comes to growing. It is really important to select a cultivar that has the physical characteristics that you desire. For example, sativa dominant strains tend to be much taller than indica dominant strains.
There are also things like terpene profile and psychoactive effects that need to be considered too. Ultimately it is about finding a plant that grows well in the conditions it is to be grown in, as well as a plant that ticks all of the boxes when it is consumed by the end user.
Pruning and plant training
As mentioned above, pruning and training techniques can help growers optimise their spaces – this is true for indoor and outdoor growers.
Pruning and training can improve light penetration, airflow, and overall plant structure. Things like topping, which involves cutting the apical meristem to promote more lateral growth, can influence plant morphology. Similarly, plant tying and low-stress training (LST) can be used to promote branching and manipulate plant structures to suit what the grower wants.
There is no wrong or right way to do pruning and training, but growers tend to find what works for them in their own growing space.
This isn’t strictly an indoor vs outdoor growing consideration. However, timing the harvest correctly is crucial for ensuring optimal potency and quality. Trichome colour is a good way to get an idea of when it is time to chop plants down and begin the drying and curing process. Trichomes are resinous glands on cannabis flowers and their colour can provide an indication of peak maturity. When they are clear it’s too early, when they are cloudy to amber is generally accepted as the best time to chop. Find out more about trichome colour in another of our blogs.
Drying and Curing
Buds must be properly dried and cured to preserve their flavour, aroma, and potency. It’s best to keep drying and curing conditions consistent, which is something that controlled environments can do perfectly. However, outdoor grown plants can be dried where they are chopped and still be great. It’s entirely up to the producer at the end of the growing cycle.
Table Summarising Outdoor vs Indoor Cannabis Cultivation
Both indoor and outdoor cannabis cultivation methods have unique advantages and challenges. Indoor cultivation provides a level of control that allows for precise management of climate, lighting, and nutrients. This generally leads to higher yields per square foot and more consistent crop quality.
Indoor cultivation also enables year-round production with multiple harvests, promoting resource efficiency in terms of water and nutrient use. However, indoor cultivation often requires higher energy consumption for artificial lighting and climate control systems.
Outdoor cultivation relies on natural sunlight and is very changeable in terms of season and geography. Outdoor growing methods tend to result in larger plants with higher yields per plant. However, outdoor grown cannabis is potentially less consistent in terms of quality due to variable environmental factors.
Outdoor cultivation typically has a longer growth cycle and can be more susceptible to pests and diseases. However, it requires less energy input and can be more cost-effective, depending on the location and available resources.
Each Grower Should Choose What’s Best
Ultimately, the choice between indoor and outdoor cannabis cultivation methods depends on many factors. Consider your geographical location, climate, available resources, growing preferences and commercial viability. Indoor and outdoor methods have unique sets of benefits and challenges, and growers should carefully consider these factors when deciding on the best approach for their specific situation. By understanding the advantages and limitations of each method, cultivators can make informed decisions that maximise efficiency, sustainability, and overall crop quality.