growing weed in a small greenhouse

Controlling your greenhouse climate is essential to producing a quality product. Some greenhouses have windows or paneling that can be opened or removed to either allow for wind circulation and to cool plants, or to trap in heat.

On a hot day, you experience the science behind a greenhouse when getting into a parked car that has been left in the sun.

A common practice among greenhouse farmers is to run cycles of plants known as “light deps”—short for “light deprivation”—during the summer season. By cutting off the amount of light a cannabis plant gets before the end of the season, you can trick it into flowering early. This will allow you to pull a crop early, which is key if you live in a climate that gets cold and wet early in the fall—you’ll want to harvest before the rain sets in and causes your buds to get moldy.

They also allow for year-round cultivation, climate control, and a controlled exposure to sunlight. What’s more, they’re cheaper than growing indoors and produce a more consistent product than fully outdoor grows.

Greenhouses also provide cover for your plants, as heavy rains will damaged them and cause them to rot if too much moisture is trapped inside the buds. Some can also have dehumidifiers, heaters, air conditioners, and fans, all of which will also regulate the climate.

Weather and Climate Control.

This greenhouse effect opens up the door to year-round cultivation, but cannabis still needs light from the sun in addition to the warmth that a greenhouse provides.

Cannabis generally goes in the ground outside between April and July, when the sun is out for most of the day. This keeps plants in the vegetative stage.

During the winter solstice in Seattle, for example, there’s less than nine hours of daylight, and the light that is available is low in the sky and poor for growing. This light and energy will still help heat the greenhouse, but you would need to use supplemental lighting to extend the hours of light in the day in order to get a quality product.

Advanced greenhouses can allow you to grow year-round by controlling light. They can provide supplemental lighting when it’s too dark outside and they can block out all incoming light if it’s too light outside.

Greenhouses are a great, inexpensive way to cultivate cannabis. They harness the power of the sun, provide a warm climate, and protect gardens from harsh environmental conditions.

In turn, soil and plants release energy as infrared radiation, which can’t escape the greenhouse, so the trapped heat warms the air.

Supplemental lighting allows the grower to extend the hours of daylight and to improve the quality of light on overcast days. This will give you more control over the vegetative state of your plants.

Once cannabis starts getting 12 hours of light or less, it’ll start flowering and producing buds. This happens outdoors at the end of summer, when days start to get shorter.

Solar radiation (energy from the sun) passes through the transparent walls of a greenhouse and heats up soil and plants, keeping a greenhouse warm even when the outside air temperature is cold.

If you want to continue growing cannabis through the fall and winter, you will have to lean more heavily on supplemental lighting and heaters.

Recreating the Cannabis Life Cycle.

The ability to control light and keep the climate stable will allow for year-round cultivation just like indoor growing. But growing outdoors and with a greenhouse is a lot more inexpensive than growing indoors, and you’ll save a lot of money on electricity costs. Even if you need to supplement light in a greenhouse, it’ll still be cheaper than the energy needed to power an indoor operation.

Manipulating Life Cycles.

A greenhouse provides the best attributes of both indoor and outdoor cannabis growing. But don’t think that building your own greenhouse means a difficult or expensive endeavour. A simple greenhouse doesn’t cost much, and all you need is a suitable space in your garden or on your balcony to get started growing cannabis like a pro. Read on to learn how to grow cannabis easily, and successfully, in your own greenhouse!

For many growers, a greenhouse is an easier and more practical option than an indoor grow room. It provides all the perks of outdoor cultivation, like natural sunlight, yet offers protection from the elements, insects, and animals.

Likewise, a simple oscillating stand fan gently blowing air across your plants can prevent pockets of stagnant, humid air from forming. You should also keep a thermometer and hygrometer in your greenhouse. Just keep an eye on these things and your cannabis will thrive!


However, you will want a power outlet nearby if you plan to equip your greenhouse with grow lights, fans, and/or an exhaust system.

Building and growing in a greenhouse aren’t as difficult as you might think. Read on to discover the benefits, and the ideal greenhouse setup for you!

When growing feminized photoperiod strains, you have the choice to use exclusively natural sunlight, or you can supplement with artificial light. If you grow in natural sunlight only, your plants will essentially have to follow the regular outdoor grow season schedule. At the end of summer, plants will start to flower, and then you can harvest sometime in autumn. Luckily, the controlled conditions of a greenhouse can support flowering deeper into fall, which is a major benefit for sativa growers especially.

You want a location for your greenhouse that isn’t exposed to strong wind and weather. A sheltered area behind your house, or somewhere tucked away on your terrace or balcony, can be optimal. If you plan to build a greenhouse in a less sheltered place, like in the middle of your garden, this will need to be professionally constructed and anchored in place. Otherwise, a strong gust of wind could be enough to blow your greenhouse away.

To keep your plants happy, make sure there is good air circulation in your greenhouse. Some of the above methods for temperature control will also help keep humidity in check. You could also leave the greenhouse door open for periods of time, and again, can cut holes into the sheeting where necessary.

• Shelter from wind and rain.


Aside from rain, humidity is rarely an issue outdoors as there will always be a nice breeze. But in a greenhouse, excessive humidity can quickly lead to an unhealthy growing environment that facilitates mould and bud rot.

Let’s start with autoflowering cannabis. The features that make autos popular among indoor cultivators are largely the same among greenhouse growers. This includes their compact size, fast growth, and, of course, their ability to flower based on age, rather than light cycle.

The short life cycle of autoflowers is a key advantage to growers of all types. Taking 60–70 days from seed to harvest on average, this is extremely short in comparison to feminized photoperiod strains, which take this long just to flower. In a greenhouse, this feature allows growers to reap multiple harvests per year and per season.

Where you place your greenhouse is very important, for a number of reasons:


By supplementing your grow with artificial lighting, however, you no longer need to follow the outdoor grow season if you choose. Instead, you can calculate an ideal sunlight/grow-light schedule to capitalise on the free power of the sun, while benefiting from the control offered by grow lights.

Supplemental grow lights aren’t just good for greenhouse growers in regions without much sun; they can be beneficial for growers in any location. Even in sunny climates, an additional grow light can get your plants through the cloudy days. Plus, if you live somewhere with a chilly climate, a powerful HPS light can support adequate temperatures for your plants.

• Growing feminized (photoperiod) cannabis.

• Water and drainage.

If you build a simple PVC greenhouse, you can make it so the windows open during the sunny months. If the greenhouse doesn’t have openings, you can easily cut the plastic sheeting to provide some nice airflow. More elaborate greenhouses can be made with windows that open and close, and some are even automated.

Invest in top-quality soil as this will impact the entire growing process. Photo by: Gina Coleman/Weedmaps.

Think about the storage space you’ll need for your greenhouse setup, including supplemental lighting and nutritional blends. You’ll also need an easily accessible place to store water and soil, so that the greenhouse is a one-stop location for all your cannabis cultivation items.

When planning to build your own marijuana greenhouse, consider which material will create the ideal environment for happy plants. While glass is the traditional material, you can also use fiberglass or plastic. The latter two will be equally effective but not as fragile or expensive. Whichever material you choose, make sure you install proper ventilation to release trapped heat and let your plants breathe.

Size and panel opacity: Aside from type and material, two other greenhouse considerations are size and panel opacity. When deciding on size, think about what strains you might want to grow and how tall they might get. A good general rule of thumb is to get a larger greenhouse than the one you think you’ll need. If you don’t need the extra room for equipment and maneuverability, you can always add more plants. As for panel opacity, clear might seem like the best choices but the sun beating down on your cannabis plants can lead to competition in young plants and hot spots later. Diffuse or semi-diffuse panels provide ample, even light, preventing hot spots, competition, and uneven growth. All that should equal better yields.

Cold frames: Cold frames are another affordable choice, though they are small and temporary. While it’s possible to construct a cold frame yourself, you can purchase a solid one for between $80 and $200, depending on the size. Cold frames are generally small boxes that sit on the ground. They are constructed out of wood or plastic frames with plastic or glass panels. Cold frames are normally used as is, with only heat from the sun, especially in warm, dry climates like Southern California. In areas with colder temperatures, consider installing a heating system, also known as a hotbed.

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Whether you want to grow recreational weed or medical marijuana, the best greenhouse may be one that you build yourself. If you have the time and skills (or helpers) to construct your own greenhouse, this route will be the most cost-effective.

Lighting: A greenhouse gives cannabis plants the benefit of natural light without exposure to the harmful environmental stressors of outdoor grows. Using natural sunlight is energy efficient, so you can save money on electricity costs by not using artificial lighting.

If DIY is not your style, think about your budget and how many plants you’ll want to grow then decide how much space you’ll need for plants, climate control, and the rest of your greenhouse setup. Armed with that information, consider the options below.

Whether it’s a simple walk-in greenhouse or something more elaborate, check local laws to see if building permits or other formalities need attention before you start building.

Free-standing greenhouses: From a simple walk-in greenhouse with room for a couple of plants to the massive connected behemoths set up by commercial growers, free-standing greenhouses are what most people picture when they think of a greenhouse. They are apex shaped, like a house, and consist of metal or wood frames and glass, fiberglass, or plastic panels. Many have roof and/or side panels that open to allow for ventilation. This may be the most expensive option, but it also has the most room for plants while still allowing for location flexibility so growers can move it to best capture the sunlight. Inexpensive free-standing models start at less than $100 but they may not be very durable. Sturdier models cost closer to $1,000 and prices go up from there.

The key word when it comes to growing cannabis in a greenhouse is control. Greenhouse cultivation provides the natural sunlight, fresh air, and other benefits of growing outdoors while eliminating the unpredictability of Mother Nature. Periods of rain and wind can wreak havoc on your weed garden, but a greenhouse protects plants from the elements. Likewise, pests, bacteria, and diseases are less likely to invade your plants in the shelter of a greenhouse.

Knowledge: The most high-tech equipment won’t matter unless you have a thorough foundation in how to grow cannabis. This means understanding when seeds should be sown (generally April), when flowering occurs (eight to 12 weeks typically), and which cannabis strains do best in greenhouses (autoflowering strains such as Purple Punch Auto, Jack Herer, and 8-Ball Kush enjoy a great reputation among cannabis growers).

Soil: First and foremost, invest in top-quality soil as this will impact the entire growing process. Pick a nutrient-packed soil that contains organic substances like compost and worm castings. Pay attention to the pH levels of the soil as well — aim for a range of 5.8 to 6.3. Other qualities to look for in soil include good drainage ability, high oxygen levels, and effective water retention. You could also make your own super soil.

In this guide, you’ll learn why growing marijuana in a greenhouse can be effective and how to get started.

The key word when it comes to cannabis growing in a greenhouse is control. Photo by: Damien Robertson/Weedmaps.

Building a cannabis greenhouse.

Polytunnel: These elongated, dome-topped greenhouses have an aluminum frame and a covering of polythene. They are usually big enough to walk into but not as sturdy as actual greenhouses. Accordingly, polytunnels are on the lower end of the price range, starting at around $160. These can be durable but do need some maintenance, especially replacement of the cover every three to five years.

Equipment: From irrigation to climate-control systems to exhaust fans, the supply list for a cannabis greenhouse can be long. But once you make an initial investment, most equipment will last season to season. Down the road, don’t be afraid to add things like heating or lighting if your cannabis plants seem to need it.

A marijuana greenhouse also puts you in control of two primary factors in successfully growing marijuana plants.

Attached greenhouses : These are usually shaped like a house and attached to the existing wall of a house, garage, shed, or barn. This greenhouse option is made of metal or wood framing with glass, fiberglass, or plastic panels. While they might be slightly less expensive than free-standing greenhouses because one wall is already built, the location of attached models is dictated by the location of the existing structure. Prices vary greatly depending on location, size, and construction materials.

Once you have the best greenhouse for you, it’s time to put your cannabis cultivation skills to the test. Here are the most important aspects of growing top-quality weed in a greenhouse.

The ideal spot for your DIY grow room will be facing the sun. A slightly shaded area is fine, but make sure nothing is keeping the natural light from reaching your greenhouse. The more hours of light, the bigger the yield.

Climate: In addition to protection from rain and wind, marijuana greenhouses can contain climate control equipment like dehumidifiers, exhaust fans, and heating and cooling systems. With the help of these tools, greenhouses can extend the growing season and allow for year-round cultivation.

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Cannabis cultivation can take place indoors, outdoors, or in a combination of these two places: the greenhouse. A greenhouse can be as small as a tool shed or as large as an industrial building. If you have enough space to accommodate even a small greenhouse, this option may propel your cannabis cultivation to the next level.

When considering greenhouse cultivation, think about how much control you would like to have over your crops. If reliable conditions make growing cannabis a more enjoyable experience for you, then a greenhouse may be the way to go. Also, assess how much elbow grease you want to put into the growing process and if you want to build a structure from the ground up. Finally, evaluate your budget and cultivation goals before you make the decision to grow marijuana in a greenhouse. Whether you choose to grow weed outdoors, indoors, or in a greenhouse, raising plants from seed to harvest can be a rewarding experience.