Growing Cannabis in a Greenhouse

Start Growing Cannabis Plants In Greenhouse

Greenhouse is very large, transparent growing area. Greenhouses are often used for growing all kinds of vegetables and as starting grow place for cannabis.

It’s place where you can start your cannabis grow and you will provide it with optimal growing conditions until they reach harvesting time.

Growers who can’t install their own grow room because of little grow space or prefer not to because of costs often grow in greenhouse.

Cultivating outdoors in greenhouse is different than regular outdoor grow and growing indoors.

Outside, plants are exposed to much more wind and rain, than greenhouse which are watertight and well-insulated against cold.

In addition, lighting is different outside than inside of greenhouse, so you’ll have to take this into consideration when choosing strain to grow.

Benefits

Growing in greenhouse has many advantages: temperature is warmer, it rains less, and you have much more space.

• More light than indoors: More light means faster growth and more significant yield
• Produces higher quality bud
• Buds are more extensive and heavier
• Plants can get big with right climate conditions (you can get up to 10 pound (4.5 kg) plants)
• You get an early starting
• More time to develop buds

Disadvantages

Greenhouse growing is ideal for outdoor professional and commercial grower who want to produce top quality outdoor weed. But there are also some disadvantages.

• Easier to see your plants from outside, and possible thieves will spot your greenhouse more easily.
• More difficult to control temperature, humidity, and ventilation. It’s easier in an indoor grow room where you can install air conditioning, ventilators, and humidifiers.
• Possibility of water leaks or snow on roof of your greenhouse can cause damage to your plants because of excess moisture in air.
• Disadvantage of greenhouse growing is that you must be careful with bugs. Especially in spring and summer, you’ll have to check your plants daily. If you see any bug, you can’t just take pyrethrum or neem spray and shake it into your plants.
• Plants will suffer from stress if temperature rises too much and they do not grow optimally. 
• And last but not least, if humidity is too high, it can lead to fungi.

Guide To Growing Cannabis In A Greenhouse

How to begin growing marijuana in greenhouse? Follow this step-by-step guide to learn growing perfect buds in your greenhouse.

Step By Step

This is what you should consider when growing outdoors in greenhouse:

• Climate of your greenhouse
• Light
• Ventilation
• Temperature
• Fertilizer and nutrients
• Pests and diseases

Which Strain To Choose

There are many different types of cannabis, each with its own characteristics. Some strains grow faster, some slower,some grow better in mild climate and some grow better in colder climates. Look for an outdoor strain that grows fast and can withstand your local climate.

Outdoor greenhouses growers can choose between Sativa and Indica hybrids. Sativa is more suitable for warm climates, whereas Indica do well in colder conditions.

Ideal Climate

If you have suitable climate, things will go great, and you can expect quality outdoor buds.

If temperature gets too high or humidity drops too low, you can always add ventilator to greenhouse or extra water your cannabis.

Greenhouse is there to help you, not to complicate things.

Temperature and Humidity

Grower should keep temperature between 70 and 80 degrees F (21 – 26 °C) during day and between 60 and 70 degrees F (15 – 21 °C) during night.

Humidity is higher in greenhouse than in regular grow room. It’s no problem if plant gets wet, but it shouldn’t get too wet or too dry.

You can solve this by placing humidifiers in room to increase humidity.

If humidity is too high, you can use an extractor to blow some fresh air into room to lower humidity.

Fertilizer and nutrients

Because you’re growing outside in a greenhouse, you’ll have to bring your plant everything it needs.

You have to give it all kinds of minerals through fertilizers.

Plant absorb these minerals through its roots and use them to create proteins, sugars, and fats.

Roots also transport water through plants, and they attract certain types of insects and birds. Last but not least, they protect plant from diseases.

Indoors, you can use liquid fertilizer every week or every two weeks. This gives your plants constant supply of nutrients for whole month or half month.

You will have to provide your plants with nutrients. Greenhouses are closed system, so there’s no way for new nutrients to be added and old ones to be removed.

Make sure you buy complete fertilizer that contains all basic elements your cannabis need: nitrogen, phosphor, and potassium.

You should give your plants two feeds during grow stage and one during flowering stage.

During growing stage, you should give them feed every week with a nitrogen content of about 5. You could also use booster.

You will have to give your plants nutrients during growing stage. During flowering, they’ll get most of nutrients they need from plant itself, but you’ll have to provide them with everything during grow stage. You’ll either have to use organic fertilizers or actinic ones.

Actinic fertilizers contain phosphor, nitrogen, and potassium and help with grow of leaves, roots, and flowers.

Organic fertilizers are made from organic materials such as grass clippings, wood chips, animal manure, bat guano, and fish emulsion.

These contain all nutrients plants need but take longer to be absorbed by plants because they’re more difficult to process.

Pests and diseases

Outside, you’re always at risk of bugs and diseases. Best way to prevent this is by growing resistant strains. If you still have issues, it’s best to learn to take preventive measures by spraying your plants.

Greenhouse is very nice place for bugs to hang out. Especially if you’re growing outdoors. There are lots of birds and other animals that will dig up your soil, looking for worms and other creepy crawlies to eat.

You should, therefore, use net around your greenhouse to keep these animals out, especially birds.

Greenhouse growers are very much at mercy of fauna that can be found outside. Sometimes they’re lucky and don’t have any visits from deer or rabbits, but there are always birds looking for something to eat.

I had huge problem with sparrows when I grew outdoors in greenhouse. They ate all my buds because they’re so small and can get away with it. If you place scarecrows near your plants, this will work fine.

Other things to keep an eye out for are wasps and flies. They can sometimes cause significant damage to your plants.

You could hang up some flypaper or put up another kind of predator. Another option is spraying plant with fly spray.

Greenhouse growers are more vulnerable to attacks from harmful creatures. Especially when you don’t do anything against it. Here’s what you could encounter in your greenhouse:

• Fungi: rot of roots, stems, and leaves
• Bugs: white flies, thrips, caterpillars
• Caterpillars: various species of butterflies and moths can lay eggs in your plants.

You can recognize some problems by looking at leaves of your cannabis plants:

• Yellowing: plant is lacking nitrogen. Leaves turn yellow.
• Purple color: plant lacks phosphor. Leaves turn purple.
• Brown spots on leaves: plant is affected by bugs or diseases.
• White spots on leaves: calcium deficiency. Plant needs more calcium.

Greenhouse Growing Outdoor Vs Indoor

Outdoor greenhouse cultivation has many advantages.

Plant is exposed to much more light and will grow faster because they can photosynthesize around clock.

Also, plant gets its water from rain and doesn’t depend on you having to give it water with spray or hose.

Disadvantage is that you have to protect your plants against animals and birds who might damage your plants by eating leaves or fruits.

Another disadvantage is that you’re dependent on climate outside, so you can’t control temperature as well as in an indoor growing tent.

Indoor Grow

In grow room, you can regulate climate to your liking. You can install extractors, carbon filters, and humidifiers. You can install lighting of your choice, start with 600 watt MH for every 12 square feet and work your way up.

You could also use HPS or sodium vapor lighting, but these are much more expensive and not necessary.

You can also create an extra climate by installing an extraction system that sucks up hot air off floor and blows cold air through ceiling fan.

This way, you can keep temperature between 73 and 77 degrees during day. Make sure you have carbon filter to catch odors coming from plants.

Lamps can be placed very close to plants when grown indoors. Light will be absorbed by leaves, and stems can’t spread out as much.

Plants are also smaller and have more stealth grow, so that you can place many more in same room. These are all advantages of growing indoors.

Indoors you can grow in grow room, warehouse, or grow tent; except for this, you can also grow in an indoor mini greenhouse.

If you want to start growing in winter but don’t have room for full-size greenhouse, you can also start in small mini greenhouse.

These are usually very cheap, small, and modern and almost always have lighting included.

Outdoor Greenhouse

Outdoor greenhouse growth is usually in full sun because it’s outside. Your plants will, therefor, absorb more light than indoor plants.

This is an advantage because plant can develop better and bigger buds. Disadvantage is that your plants are more vulnerable to fungi and bugs, because they can fly or walk to them.

Indoor greenhouses are also nice, but they’re placed inside buildings and are not exposed to full sun as outdoor greenhouses.

Outdoor greenhouse growth is usually in full sun because it’s outside. Your plants will, therefor, absorb more light than indoor plants.

This is an advantage because plant can develop better and bigger buds. Disadvantage is that your plants are more vulnerable to fungi and bugs, because they can fly or walk to them.

Indoor greenhouses are also nice, but they’re placed inside buildings and are not exposed to full sun as outdoor greenhouses.

You typically choose an outdoor greenhouse when you’re growing on large scale. Greenhouse is much more expensive than growing outdoors in field like cannabis farm, but it does offer some advantages.

In greenhouse, you can control temperature and humidity exactly, so no bud rot or mold will occur. You can also create an artificial light source if need be to make sure plants get enough light.

Outdoor greenhouse is usually enough to grow many plants at same time during summer months.

Outdoor growers who don’t have access to greenhouse can still grow cannabis in their backyard.

Plant needs to be sheltered from wind and rain, so garden shed or simple wooden warehouse will do fine.

Greenhouse is very suitable for growing cannabis outdoors, and you can also do this in regular tent or a shed with green roof.  

Outdoor Vs Indoor Quality

Outdoor grown weed will always be superior to indoor grown weed. Outdoor buds will always be bigger, smellier, and have higher THC content.

Outdoor growers can take advantage of outdoor growing season, with its warm days, cool nights, and rainy days.

Indoor growers don’t have this luxury and are therefore limited in their growth cycle. Indoor growers can only starts their grow during winter, which will force them to finish by spring.

Indoor plants also don’t have chance to develop as much as outdoor plants do because they are kept in small spaces. Outdoors they can stretch out towards sunlight and process more CO2 through their leaves than indoors.

Outdoor cannabis yield is, therefore, almost always better than indoor yield. If you want highest possible yield with average quality buds, then go for outside greenhouse grow.

Outdoor greenhouse yields are about 30% higher than indoor yields.

Outdoor greenhouse is climate controlled and can supply plants with all neccessary water and nutrients.

Indoor yield can’t compete with outdoor greenhouse yield, but it’s still very decent.

And you have more control over entire process in an indoor grow tent, so you get better quality weed.

When Is Best Growing Season To Start In Greenhouse

You can start growing cannabis in a greenhouse whenever you want. However, there are certain advantages to starting growing cannabis in a greenhouse in spring time of year.

One of most significant advantages is that you won’t have to buy heater and fan for your greenhouse yet.

You can use lighting system as warmth source during early spring months. Also, soil humidity will be moderate and it’s not as cold in spring time of year.

You can start growing anytime, but it’s always best to wait until decent temperatures. If you live in northern hemisphere, you could start growing in February. 

Growth is fastest when days are longer and nights are shorter, so growing season starts when days get longer.

When To Start Growing If You Live In Australia

Since seasons are reversed in Australia, it’s best to start growing in fall. So if you order greenhouse online, it will be delivered at perfect time.

You can immediately put up greenhouse and start transplanting your cuttings in soil. Since temperature inside greenhouse is always right, you can immediately begin to grow.

If you want to grow outside during summer growing season, you have to wait untill spring to put up your greenhouse.

Growing Cannabis In Greenhouse During Winter Season

You can start growing in winter, but it will take longer for your plant to get big enough to flower.

Also, yield will be smaller than during summer growing season. Best moment to start growing is in spring.

Greenhouses are popular among people who want to start seedlings earlier in spring or grow certain flowers during fall and winter. 

 Greenhouses can be heated with cheap oil stoves or electric heating, so there’s no need to wait for nice weather outside.

If you start growing in winter, you’ll have to provide your plant with artificial light.

You can use regular fluorescents, but more powerful HPS lights are better choice.

Since days are short and temperature drops, you’ll have to provide your plant with more heat.

A 600 watt MH lamp provides about 1700 watts of power and will cost you about $60.

You could also hang couple of 400 watt HPS lamps above your plant if you want to grow some real heavyweights. Such a lamp costs $250. 

Growing Cannabis In Greenhouse During Summer Season

But what about summer? Greenhouse is not an ideal place to be in when temperatures rise above 90 degrees F.

If you’re growing in summer, you can use shade plastic netting to reduce heat from sun. Plastic will also protect your plant from harmful UV rays.

You also have to ensure your greenhouse doesn’t get too hot, so make sure you place fans well.

If you’re growing outdoors in summer, it’s good idea to use plastic netting to protect your plant.

Since sun is much stronger during this growing season, plant will dry out much quicker, and roots can suffer damage if not watered sufficiently.

Make sure there are no spots where no water will fall during hot days. Keep an eye on soil because that’s where roots are.

How Long Does It Take To Grow Cannabis in Greenhouse

Greenhouse is very nice climate for growing marijuana because temperature, humidity, and ventilation are all well managed.

That means you don’t have to do as much work in order to keep right climate.

Depending on your greenhouse size and your seeds’ quality, you’ll have your first harvest in about 12 weeks.

Of course, it depends if you’re growing in soil or hydro and what strains you’re using. Sativa dominant strains will grow faster than Indicas.

It always depends on type of plant, but let’s say you germinated your seeds in February.

Little plant will appear out of soil in March, you can transplant them to 12-inch pots in May, and they will be ready to harvest by the end of September.

Best Greenhouse For Growing Marijuana Seeds

I grow marijuana in a greenhouse setup that I bought at Harbor Freight. It’s nice and simple, cheap and small greenhouse.

This is really cheap greenhouse that’s climate-controlled. But it’s really easy to install yourself, and it will still do good job.

You can place greenhouse on concrete floor or on grass. 

Greenhouse comes with flaps that you can open or close to increase or decrease temperature.

In addition, flaps provide light breeze to keep plants healthy. You could also place fan somewhere if you want additional airflow.

Best Outdoor Grown Setup

Greenhouse growing outdoor is very similar to growing in regular outdoor gardens. Only difference is size and materials for cover.

Outdoor greenhouse has way bigger size than regular outdoor garden. This allows you to grow more plants at once and gives them enough space to grow big.

If you want to grow outdoors and have access to greenhouse, there are some things to take into account.

Growing outdoors, in general, is more difficult than growing indoors, so you’ll have to prepare yourself well.

Some outdoor cannabis growers also use a greenhouse or tent. Greenhouse is perfect place for budding plants because it creates perfect climate.

You can control temperature and humidity and keep light for your buds. You can get done greenhouse or make your own greenhouse setup.

Make Your Own Systems

Your greenhouse will become your outdoor growing room. Outside, you have to deal with all kinds of pests and animals.

It’s nice to be able to sit in your greenhouse on warm spring day, but you still have to keep an eye out for deer and birds.

Since greenhouse gets full sun for many hours a day so that you can grow nice and fast.

But it’s also important to provide some shade during middle of day if temperatures rise too much.

You could hang up blanket or use some plastic netting that provides shade. You can also put up an umbrella over plants if they get too much sun.

You will also need different materials for covering of greenhouse since rain and wind can easily damage traditional plastic nets or cloths.

You’ll need special materials kits that are resistant to rain, wind, cold, and heat. These include polycarbonate (PC) sheeting or polyethylene (PE) sheeting. These are both transparent plastics that provide good insulation properties and are very durable. 

You can make your own greenhouse with simple materials, such as plastic or wooden frames and waterproof foil.

It’s much cheaper than buying a ready-made greenhouse, and it also looks nicer. You also have better control over climate if you install an air conditioning system.

Cultivation Of Medical Marijuana In Greenhouse

Although growing outdoors is great fun, cannabis greenhouse will give you much better results.

In addition, medical cannabis patients can grow little more to provide themselves with sufficient supply of their medication.

Greenhouse is good alternative to growing tents because you can control climate better and provide your plants with sun they need.

Cultivating medical cannabis in greenhouse can provide controlled and protected environment for growing cannabis plants, leading to high-quality crops.

You can create cannabis greenhouse effect by hanging plastic sheeting above your plants.

It’s possible to heat greenhouse with an electric heater or even with horticultural lamp if you grow in winter.

Soil in greenhouse stays warmer longer, and plants can absorb more water because no wind will blow through.

This is disadvantage during flowering stage when plants need little fresh air. During vegetative growth stage, it’s perfect setup.

Growing marijuana in a greenhouse is perfect for growing outdoors, even in colder climates. Plants get sufficient light and can still absorb enough water when it’s raining or snowing.

However, it’s important to note that cultivation of cannabis, including for medical purposes, may still be illegal in some states, and regulations and laws may vary by state or country.

Best Strains For Growing In Greenhouse

Once you’ve built your greenhouse, it’s time to think about what cannabis plants you’re going to grow.

You have couple of options, and it all depends on climate and size of your growing greenhouse.

If you have large free-standing greenhouses, you can grow multiple plants in there. If your marijuana greenhouse is more miniature, you can only grow couple of plants.

I prefer Sativa cannabis because they grow little bit faster. But Indica cannabis is also very suitable for greenhouse cultivation. 

Outdoor grown weed is always great quality. Here are some of best cannabis seeds we offer at Dutch Seeds Shop that are suitable for greenhouse growth:

Indica

While many indica strains are suitable for greenhouses weed grow, there are some that are more ideal choices.

These include following cannabis seeds:

Northern Lights Seeds

Northern Lights is one of most well known Indica cannabis seeds in history.

It’s perfect choice for growing because it has outstanding yields, and it will grow at a reasonable height.

It’s rare strain that can be grown indoors and outdoors, making it an excellent option for greenhouses cannabis cultivation.

Blueberry Seeds

Blueberry is another classic strain that will have you feeling relaxed and calm.

Plant has amazing taste and produces dense buds thanks to their impressive yield potential.

Blue Cheese Seeds

Blue Cheese strain was first produced in Netherlands and is an indica dominant hybrid.

It has solid fruity aroma with taste to match, making it great option for those who love their bud to have unique taste and smell.

Sativa

If you’re grower who likes to stay busy, then Sativas are for you. These are fast-flowering marijuana plants with high levels of THC and low levels of CBD.

They’ll make you happy, talkative, and creative. Best greenhouse weed is Sativa dominant strain that can grow up to few feet tall.

Sativa cannabis seeds that are suitable for greenhouses cultivation include following:

Super Lemon Haze Seeds – Feminized

Super Lemon Haze is cross between Super Silver Haze and Original Lemon Skunk cannabis. This Sativa dominant strain has won many awards over past few years.

It has creamy, lemon sherbet taste with spicy, earthy undertone. THC content of Super Lemon Haze is high at around 20% and CBD at less than 1%. Plant needs more space to grow indoors and outdoors cause they will reach very tall heights.

Amnesia Haze Auto Seeds

Amnesia Haze Auto is cross between South Asian landrace Sativa and Jamaican landrace, Amnesia Haze offers unique combination of flavors and outstanding THC levels.

This plant is an excellent choice for outdoor growers as it is relatively resistant to cold. Although Amnesia Haze Auto can grow up to 2 meters, its buds take 12 weeks to finish flowering and yield up to 14 oz/plant.

First hit of smoke from Amnesia Haze Auto will reveal a sweet taste of mangoes along with smooth high that leaves you energetic and uplifted.

Sour Diesel Seeds

Sour Diesel is sativa dominant hybrid strain.

It got its name from its original smell that resembles diesel fuel.

It has quite high THC content, with 17% being average. Sour Diesel is one of most popular cannabis seeds due to its unique up-lifting and energetic effects.

This strain is best used during day as it provides users with increased focus and creativity. It also gives you that ‘rush of motivation’ feeling when used in large doses.

Sour Diesel has won fair share of awards, including Cannabis Cup in 2003 and 2008 and High Times Cup in 2014. Sour Diesel also won Best Sativa award in 2010.

Buy Seeds Online At Dutch Seeds Shop

You can get all best cannabis seeds for greenhouses cannabis cultivation at Dutch Seeds Shop. We have wide selection of best Sativas and Indicas in cannabis industry, so you’re sure to find something that fits your taste.

All our seeds are organically grown so that you can be sure of quality products. We offer different brands, but all our products meet highest quality standards.

Our greenhouses seeds are available in different packages. All our seeds are shipped with track and trace codes and are sent with priority mail.

We offer you convenient and smart packages, so you never have to worry about your order. We offer free worldwide shipping on all orders and five free seeds on orders that are above 100$.

FAQ

Let’s learn with most important question about growing cannabis in greenhouses and give some answers; 

How much space do you need to grow your own medical marijuana in greenhouse?

Answer is simple; as much as you can get. It’s nice to have space for different plants to grow at different stages.

You can’t determine number of plants based on size of your greenhouses because you’ll need some space between them to let them grow properly.

But if you have greenhouses at your disposal, you’re already halfway there!

What type of equipment is needed?

Greenhouse doesn’t come with all equipment you need to start growing. You’ll have to buy some of it.

You’ll need water system and ventilation for some sort of climate control.

Air conditioner: when growing outdoors, you’re at mercy of mother nature. If heat wave hits, it gets very hot inside your greenhouses.

That’s why you should have powerful air conditioner to blow cold air into your greenhouses. You could also use sprinklers that are activated by temperature sensors to cool down tent when it gets too warm during sunny days.

Water system for greenhouse is very similar to one you would use for grow tent or in your basement.

You will have to connect it to water tank, from which it will feed your plants via drippers and net pots. Make sure system has enough capacity.

Can greenhouses be too hot for cannabis?

No, greenhouses are colder than outdoors because of their walls and roof.

Also, you can create micro-climate by opening or closing vent or door. You can also install air conditioning.

About the Author

Born in Serbia, Nenad is a renowned cannabis grower, consolier, and writer. Educated in botany, he became a key figure in European cannabis culture, authoring influential works and creating his unique brand.

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