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How to Grow Cannabis in a Greenhouse: A Guide

Growing cannabis in a greenhouse is an effective cultivation method that combines the perks of outdoor growing with those of indoor cultivation. Learn all about it below!

Learn to grow cannabis in a greenhouse.

Contents:

Growing cannabis in a greenhouse is ideal because it combines the benefits of outdoor growing with those of indoor cultivation. In this guide, we’ll show you how to do it, offering tips and advice as we go along. If you don’t have a greenhouse yet, and want to build one, we can show you how to do that, too.

WHY GROW CANNABIS IN A GREENHOUSE?

Maybe you’re wondering why you’d want to grow weed in a greenhouse, as opposed to growing indoors in a tent or having an ordinary outdoor grow in your garden. Let’s look at the advantages of greenhouse cultivation over other growing methods.

YOU CAN EXTEND YOUR GROWING CYCLE

You can extend the cultivation period into the fall and winter seasons simply by adding more light during cloudy days, and progressively keeping them on longer to compensate for shorter daylight hours. Likewise, if you want to start a new grow before the end of winter, you can add a low-powered light to supplement natural daylight.

PROVIDES THE IDEAL MICROCLIMATE FOR GROWING CANNABIS

A greenhouse environment can sustain higher average temperatures than chilly open fields or gardens. Plus, during cold or hot seasons, you can heat or cool a greenhouse if needed. Even without a heater or cooling system, a greenhouse will provide a more consistent range of maximum and minimum temperatures, without the extremely dry and hot conditions typical for indoor grow rooms. A more consistent microclimate means healthier plants and bigger harvests.

ALLOWS FOR YEAR-ROUND CULTIVATION

The climate within greenhouses can easily be controlled, for instance by opening windows or installing fans. And, since the walls of a greenhouse keep humidity and heat inside, it allows for year-round cultivation. This control over climate and exposure to light isn’t possible in regular outdoor cultivation.

MORE CONSISTENT HARVESTS

Greenhouse harvests tend to be more consistent over time, both in quantity and quality. This is also why the majority of commercial medicinal cannabis produced today is grown in greenhouses.

MORE ENERGY-EFFICIENT THAN INDOOR GROWING

Since cultivators can take advantage of natural sunlight, growing in a greenhouse is way more energy efficient. You will also have much lower electricity costs compared to growing in a room or tent.

PROVIDES PROTECTION FROM THE ELEMENTS

Unlike outdoor cultivation, a greenhouse protects your plants from the elements. There is no threat of rainfall or storms harming your precious ladies. In addition, a greenhouse prevents scavenger animals from having their way with your crops.

KEEPS PLANTS SAFE FROM DETECTION

A greenhouse allows for discreet growing with a greatly decreased risk of detection. Your plants will be safe and secure, so you can go to sleep without worrying about thieves and vandals.

IT’S NOT EXPENSIVE

Growers don’t need to spend a lot of money to set up a greenhouse. A simple walk-in greenhouse can be purchased for little money, and will do a decent job of housing your plants. Building a DIY greenhouse is another inexpensive option. For a simple grow using natural light and hand-watering, there’s no need for expensive grow equipment.

HOW TO GROW WEED IN A GREENHOUSE?

Growing cannabis in general involves many variables that need to be kept in check. Growing in a greenhouse is no exception. However, differences in methodology from indoor and outdoor cultivation need to be taken into account. Here is a list of steps you can take to run a successful greenhouse grow.

PICK A SUITABLE STRAIN

Cannabis strains differ in how they grow, and in regards to their requirements. The best type of cannabis for your greenhouse setup ultimately depends on a number of factors, including your local climate, available space, and whether you’re planning to use an artificial grow light. Let’s dig in a little deeper:

AUTOFLOWERING SEEDS

Autoflowering cannabis is optimal if you’re growing using natural sunlight. As autoflowers don’t require a set light schedule to veg and flower, variations in sun exposure won’t harm your plants or diminish yields as much as photo-feminized plants. This also means you can plant and harvest autos in your greenhouse at any time of year—as long as you support ideal environmental conditions.

Lastly, the smaller size of most autoflowering varieties comes in handy if space is constrained, which is usually the case with small greenhouse setups. To make up for lower yields from smaller plants, you can simply grow more of them in your available space (e.g. the sea of green method).

FEMINIZED SEEDS

Growing photoperiod feminized cannabis is also possible in a greenhouse, but comes with some constraints, especially if you’re using exclusively natural light. As these strains flower based on the hours of light they receive, you rely on the seasons to support vegetation and stimulate flowering.

However, you could also set up an artificial grow light on a timer to control your plant’s development. But then you may also need to look into making your greenhouse light-proof. Otherwise, the natural daylight could interfere with your artificial light schedule, causing its own issues.

Another issue when growing photo-feminized plants in a greenhouse is that you may need to train and prune your ladies to prevent them from growing out of contol. Especially if you’re using only sunlight, plants can get tall and spindly, and may require some topping, scrogging, and the like to remain at a reasonable height.

PLAN YOUR GROW WINDOW

With natural light as the main source of energy in your greenhouse, you need to plan your grow window accordingly. Ideally, you want to be ready as soon as daylight hours (and temperatures) start increasing in spring.

Even though your greenhouse will maintain higher temperatures than those outdoors, you should wait until there is no risk of frost before bringing your plants into the structure. Depending on your location and local climate, this may be early or quite late in spring.

GERMINATE INDOORS

Building on the above, you can always germinate your seeds indoors and start nurturing your plants with low-powered CFLs to give them a head start. You won’t need much space for this, and CFLs tend to run cheap. This way, even if the rest of your grow is conducted using sunlight, you can still take full advantage of the outdoor growing season.

MOVE SEEDLINGS TO THE GREENHOUSE GRADUALLY

As soon as your plants get a little bigger and stronger, after about a week or two, you can gradually get them used to their new growing environment. Go easy on them, and don’t move them abruptly from the cosy indoors to the greenhouse. Set them in the structure for just a couple of hours each day and increase over the first few weeks.

This way, stress is reduced and plants can continue to develop without a hitch. Your plants are sensitive, especially at this stage, so don’t use your greenhouse as an excuse to be negligent.

SUPPLEMENT LIGHTING ACCORDING TO WEATHER

One of the great things about greenhouses is that they allow growers to supplement natural lighting with an extra grow light. Stretches of poor/cloudy weather can be overcome without fear of a diminished harvest, and your electricity bill will be vastly lower than if you grow indoors.

Then again, if one is growing in a suitable climate with plenty of sun, a supplemental light may not be necessary. Still, having one at the ready is never a bad thing for a cannabis grower.

USE BLINDS OR COVERS TO FORCE FLOWERING

A greenhouse makes it possible to force-flower cannabis using light deprivation techniques. Elaborate timed shutters could be installed to obscure plants for this purpose, but simple blackout covers or blinds can also do the trick—at a fraction of the price and with much less effort.

In addition to allowing you to flower your weed at any time, blackout covers also serve to prevent cannabis light pollution (e.g. nearby street lighting), which could otherwise interfere with flowering for photo-feminized plants.

PRO TIPS FOR GROWING CANNABIS IN A GREENHOUSE

You want your cannabis to be happy, comfortable, and productive in your greenhouse grow-op. So, what else do you need to know to achieve a great harvest? Check out our pro tips below.

In this article, we cover how to successfully grow cannabis in a greenhouse. Learn the pros of greenhouse weed cultivation and get your own grow started today!

Grow Weed Easily And Successfully By Building A Greenhouse

Published : Mar 16, 2020

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!

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!

BENEFITS OF GROWING CANNABIS IN A 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.

For growers in cooler regions of the world, a greenhouse can also provide a longer growing season. You can, for example, plant your seeds earlier each season, as well as harvest later if need be—and you don’t need to worry as much about cold temperatures and rain. You also have the option to heat and cool your greenhouse, supporting ideal conditions for growing top-quality weed rivalling that of warm-weather growers.

Aside from offering protection from wind, rain, and frost, a greenhouse has a lot of other benefits. For example, you can equip your greenhouse with artificial lighting to take advantage of grow lamps and natural sunlight. This way, you can control a plant’s vegging and flowering phases as if you were growing indoors. Moreover, if you set up a small greenhouse on your balcony or terrace, it can be a good way to keep suspicious odours and noise from being an issue indoors.

WHAT TYPES OF CANNABIS CAN YOU GROW IN A GREENHOUSE?

You can grow all types of cannabis in a greenhouse with great success. Here are some specifics about autoflowers versus photoperiod plants:

• Growing autoflowering cannabis

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.

When it comes to size, autoflowers often max-out at a metre or less in height, with some cultivars reaching only 50cm. This makes them excellent candidates for smaller greenhouses, such as those on a balcony. Moreover, some greenhouse growers like that you can cram several autos into a relatively small space to increase yield.

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.

In terms of light cycle, autoflowers allow growers to plant at basically any time of year, as long as there is enough artificial light to support robust growth.

• Growing feminized (photoperiod) cannabis

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.

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.

HOW LARGE CAN YOUR GREENHOUSE CANNABIS PLANTS GET?

Given ideal environmental conditions are met, your plants can, in principle, grow just as large in a greenhouse as they can outdoors. It’s not uncommon for cultivators to harvest 2–3m-tall monsters, or even taller. Of course, this all depends on how much space you have in your greenhouse and how large of a plant you want to deal with. Even if you don’t have a super tall space, you can still potentially grow sativas and other lanky strains using training techniques. Simple LST can keep vertical growth in check, and techniques like topping can help to boost yield while breaking apical dominance. You can also keep height in check by skipping the vegetative phase and initiating flowering right away.

PLANNING AND BUILDING YOUR GREENHOUSE: THINGS TO CONSIDER

You can build and purchase greenhouses of virtually all sizes, from simple mini-greenhouses to custom-built, full-fledged extensions for your home. You can find greenhouses consisting of a transparent PVC sheet over a metal or wooden frame, some that use polycarbonate plastic panels, and others made from glass. Some types of greenhouses are designed to be situated against a wall of your home so the heat keeps the greenhouse warm.

A simple walk-in greenhouse with a metal frame and a sturdy PVC sheet with a zipper door can be purchased for little money. These are great if you’re on a budget and/or you don’t want to go all out building a greenhouse from scratch.

WHAT MAKES A GOOD GREENHOUSE LOCATION?

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

The location of your greenhouse will ultimately determine how much sun your plants receive. Obviously, you don’t want to place your greenhouse behind your house in the northern part of your garden where your plants never get any sun. The best location is the south or southeast side of your house.

On the other hand, if you live in a hot and sunny climate like the Mediterranean, you may want your greenhouse in a shaded location. Likewise, if you plan to mostly use artificial lighting, it matters less where you greenhouse is located in relation to the sun.

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

• Shelter from wind and rain

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.

• Water and drainage

Another important consideration: Is a water connection and drainage nearby? You don’t want to be lugging buckets of water to your plants or draining the runoff into the middle of your garden. Having water and drainage available is also important if at some point you decide to automate your system or implement hydroponics. Some hydroponic systems may require changing the tank every few weeks. If your greenhouse is on your balcony and there is no way to empty or fill the tank, short of carrying the tank into your house bathroom, this could be an issue.

GROWING CANNABIS IN A GREENHOUSE WITH ARTIFICIAL LIGHTING

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.

Another big benefit of having a grow light in your greenhouse is that you can extend the hours of light your plants receive. For example, you can use the lights to provide your vegging photoperiod plants with 18–20 hours of light, even when natural daylight hours would be much shorter. This allows you to grow your plants all year long—plus it will greatly increase your yield.

EARLY FLOWERING WITH AN AUTOMATED DARKENING SYSTEM

In addition to artificial light, you can also install a darkening system in your greenhouse. Such systems usually consist of automated blinds or a curtain on a timer, and allow you to induce and support flowering even when the days are long and sunny. With a darkening system, you are able to simulate the shorter days in fall. Put your plants under a 12 hours on, 12 hours off light cycle to initiate flowering. Pro greenhouse growers time their light-dark cycles so they can plant and harvest cannabis all year long!

CONSIDER HEAT AND HUMIDITY WHEN BUILDING YOUR GREENHOUSE

At times, a greenhouse may also bring with it some issues. One of them is the potential for the space to get extremely hot and humid, and this can happen quite quickly depending on the climate and positioning of the structure.

When the sun is shining into your greenhouse, temperatures can rise to dangerous levels for your plants. In some cases, this may only cause plants to grow slower, but once temperatures exceed 40ºC, fatalities can occur.

As such, you want to make sure that your greenhouse has optimal ventilation and cooling, and you may want to consider artificial lighting with less heat output, like LEDs.

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.

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.

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.

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!

WHY NOT BUILD YOUR OWN GREENHOUSE?

Do you desire the yield and majesty of outdoor cannabis, and the control and safety offered by indoor grows? Consider a greenhouse. Using a variety of different materials and building methods, you can customise a greenhouse to suit your needs and budget. You can build out a 220cm x 120cm walk-in greenhouse with a sturdy PVC cover over a metal frame for under €100. And once you’ve harvested your first crop of greenhouse cannabis, you can always upgrade to something more elaborate to push your plants’ potential even further.

In this guide, you'll learn how easy it is to grow great cannabis in a greenhouse. It's not that difficult or expensive to build your very own!