5 Top Tips For Growing Autoflowering Cannabis Strains in a Greenhouse

07 March 2023
In this article you will learn our 5 best tips to help get you on the way to a successful harvest, including what to avoid when growing autoflowering Cannabis strains.
07 March 2023
15 min read
5 Top Tips For Growing Autoflowering Cannabis Strains in a Greenhouse

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  • 1. Pick the right location outdoors
  • 2. Fast flowering varieties are better
  • 3. The ideal pot size
  • 4. Try building a greenhouse
  • 5. Harvest all year long
  • 6. What to avoid when growing autoflowering cultivars
  • 6. a. Avoid repotting
  • 6. b. Taking clones
  • 6. c. Excessive training
  • 6. d. Over watering
  • 6. e. Forgetting to flush
  • 6. f. Failing to control climate
  • 6. g. Low-quality materials
  • 6. h. Bad seeds
  • 6. i. Overfeeding
  • 7. How to build an easy diy tunnel greenhouse
  • 8. Best 3 recommended strains for growing autoflowering cannabis
  • 9. In conclusion

As spring approaches and we prepare our autoflowering outdoor crops, having as many tips and pieces of expert advice will help take your crop to the next level. Below you will discover 5 top tips to make you a better grower, increase yields as well as what to avoid when growing autoflowering Cannabis. Read along if you want to find out how simple changes in how you grow can result in an overall better harvest when growing autoflowers in a greenhouse!

1. Pick The Right Location Outdoors

One of the reasons why autoflowering Cannabis strains have become so popular in recent years, is down to the fact they are capable of producing top-shelf buds under the most demanding conditions. If you live in a cold and wet climate that experiences short summers and harsh winters or live in the luxury of the Mediterannean or California, autoflowering strains are extremely reliable and can be grown all year round in many cases as long as you keep the following in mind:


  • Plants facing south;
  • Avoid shaded areas and;
  • Fabric pots work best.

 Top tips for growing autos in a greenhouse: pick the right location

Top tips when growing your autoflowers outdoors.

Our top tip here is to pick the right location and think everything through before planting your seedlings straight into the ground. There is nothing worse than watching your precious cannabis become shaded after a certain point early in the daytime, so it is a good idea to grow your automatic strains in either plastic or fabric pots that can be easily moved. There are many benefits to doing this including the speedy removal of any plants in the event of an emergency. The main reason is to allow your cannabis to receive as much direct sunlight as possible, without the restriction of being planted into the outdoor soil.

2. Fast Flowering Varieties Are Better

Thanks to the recent evolution in autoflowering genetics, hope is given to those who always suffered from challenging weather such as Northern Europe, Russia, and the more harsh environments for Cannabis. Our top tip here is to find strains that will mature in time so you do not need to be concerned about the threat of rainy days, mold or mildew taking over your garden. That being said, Fast Buds pride itself on offering the fastest flowering automatic cultivars on the market. For those who have a short inconsistent summer followed by a chilling early Winter, they can find comfort in fast-flowering, rapid-growing autoflowering cannabis strains that can be harvested in as little as 10 weeks from seed until harvest. 

3. The Ideal Pot Size

The average root depth for large-sized Cannabis is close to 14 inches. This is considering a photoperiod cultivar that depends on both vegetative and flowering periods. Autoflowering Cannabis strains do not depend on a body clock in the same way and will begin flowering approximately three weeks after the seedling has sprouted. Our top tip here is to use fabric pots as they allow for the roots to be pruned, and will eliminate root-bound cannabis. The recommended size is 10L as this gives the 12-14 inches the root ball will need and allows the plants to access nutrients and minerals for the duration of the life cycle.

Of course, it is possible to grow in pots smaller than 10L, yet be prepared for a much smaller-sized plant. It can be a good idea to consider this option if your end goal is to grow a Sea of Green. However, if you're growing only growing one or two autoflowering cannabis, remember, the bigger the pot generally reflects the bigger the harvest.

4. Try Building A Greenhouse

One of the best ways to grow outdoors and with an initial low-cost investment is to build your own greenhouse. By using wooden stakes, thick bendy pipe, and a polystyrene sheet cover, building a highly durable, wind-resistant, waterproof greenhouse for your autos is easily achievable. The materials will not cost much and the life span of your greenhouse will far exceed the low cost to make. 


Top tips for growing autos in a greenhouse: polytunnels 

Greenhouses allow you to better control growing conditions.

Our top tip here is to build your greenhouse facing south, meaning your autoflowering Cannabis will receive direct sunlight until the sunsets each day. Not only will your greenhouse keep your cannabis out of sight from neighbors and helicopters, but it will allow you to grow all year round and not only Cannabis. By installing a hose pipe with spray nozzles, it is very easy to create an indoor tropical greenhouse that has the ideal temperature and humidity throughout the year. 


Pros and Cons Of Growing Cannabis In A Greenhouse
Pros Cons
Allows you to grow all year long Can be expensive
Better climate control Requires a lot of space
Helps protect against pests and bugs Equipment consumes energy

5. Harvest All Year Long

If you are fortunate to live in a sunny climate such as the Mediterranean, California or anywhere with tropical weather, you are blessed with the ability to harvest automatics all year long. If you can harvest every 70-80 days, this means you can produce a crop every quarter. Our top tip here is to invest in plenty of autoflower seeds so you can easily fill a polytunnel with a Sea of Green, perpetually every 10-12 weeks. The more seeds you plant then the more you will harvest, so get in the habit of farming all year long, making the necessary adjustments when required.

6. What To Avoid When Growing Autoflowering Cultivars

Avoid Repotting

Autoflowering Cannabis plants much prefer to be left alone once they start life. It is a wise idea to re-pot photoperiod cultivars, however with autos, transplanting them will only slow growth down and oftentimes shock the plants. Decide on the final pot size, or flower bed site you wish to sow your seedlings and then leave them. An undisturbed autoflowering plant will perform much better than one that has been moved around during the pinnacle weeks of development.

Taking Clones

It is not possible to take clones from autos and have them stay in a vegetative state. Due to the nature of the Ruderalis, the clones will begin to flower once rooted and the removal of the lower branches will be detrimental to the yield of the plants. 

Excessive Training

Avoid being too heavy when it comes to training, and stick with low-stress training and pruning. Topping and fimming can cause plants to flower at a short height.


Top tips for growing autos in a greenhouse: what to avoid

What to avoid when growing autoflowers.

Autos react very well to being tied down as it exposes the inner canopy to more direct light, enhancing growth and production. 

Over Watering

Just because your plants are autoflowering, does not mean it is necessary to hammer the plants with nutrients. This is how many inexperienced and overzealous growers overwater their roots, causing issues with nutrient uptake and inviting bad bacteria to grow around the roots. Water in moderation and treat auto the same as you would any other plant.

Forgetting To Flush

Flushing makes such a big difference to the overall experience when smoking your harvested flowers. There has to be a point where you only feed your plants plain water or a solution of water with enzymes.

Failing to Control Climate

It’s vital to provide the right growing conditions for healthy plant growth so you will need to monitor the humidity levels and temperature closely. When growing cannabis in a greenhouse, proper ventilation is vital so that the growing conditions don’t get too warm or moist. On the other hand, if the air is too cold it could also affect your plants badly, which can lead to hermie plants so make sure to have a device to measure the temperature and humidities and try to keep them as close as possible to the ideal conditions for each stage of plant growth.

Low-quality Materials

One of the most common mistakes when growing cannabis in a greenhouse is to use low-quality materials. So make sure to get the best greenhouse you can afford and, if building your own, make sure your DIY greenhouse can withstand strong wind and rain.

Bad Seeds

You won’t be able to have a good harvest without good genetics so make sure to start with quality seeds from reputable vendors or seed banks. You can also get clones if needed, it doesn’t matter if you start with clones or seeds, just make sure they’re good genetics.


Overfeeding is probably the most common mistake when growing cannabis. Over-fertilizing or overfeeding can stress autoflowers and cause them to flower early so it’s recommended using organic slow-release nutrients as they release the food gradually. Inorganic liquid nutrients will work just as well but you have to be a bit more careful, especially with autoflowers. Now, it doesn’t matter what type of fertilizers you use, make sure to follow the manufacturer's recommendations and start with half of the recommended nutrient dosage as you cannot correct an overfeeding once you’ve already fed your crop.

7. How to Build an Easy DIY Tunnel Greenhouse

So, there you have it. All of the reasons why setting up a greenhouse makes perfect sense, and the 5 top tips for greenhouse cultivation. But before you can get started on your own greenhouse cultivation journey, you will need to build one. Here you have two main options. Either head to a big box store (or online) and buy a prefabricated greenhouse - there are so many to choose from, and the assembly is usually very simple, or run down to your local hardware store and grab all the pieces of kit to build one from scratch yourself.

By DIYing it you'll end up saving some cash, but in all honesty probably not a sizeable chunk. There is one main benefit from building one from the ground up - being able to design a greenhouse to fit your location perfectly. Here’s a list of things you'll need to begin your DIY project:


  • Framework: PVC pipes are usually best - you want to grab a size that's thin enough to easily bend into semi-circles.
  • Covering Material: Clear plastic, but bear in mind that the thicker it is the more durable your greenhouse will be.
  • Cement and Bricks for Building the foundation: These are a great option for the base of your greenhouse, but may not be 100 percent necessary depending on the ground you are building on.
  • Short lengths of metal rebar - these are great for anchoring the frame.
  • Ventilation: For optimal air circulation and temperature control - this can be as simple as just leaving the two ends of the tunnel uncovered, or you may want to install some small oscillating fans for better canopy air exchange.
  • Screws and Glue: You’ll need these to join pieces of the frame together, and secure the covering material.
  • Lighting Solutions: If you plan on using artificial lighting in your greenhouse then you’ll need to get the right items - extension cords, light fittings, bulbs


Here's how you can quickly throw together a decent DIY tunnel greenhouse -


1. Start by laying out your PVC pipes and cutting them to length. The length is totally dependent on how wide your greenhouse will be, and how high you want the top of the covering to be.


2. Next, if you are going to pour a cement slap then now is the time. Again, this isn't necessary but will make life a little easier in the long run - especially if you are planning on building a large greenhouse. Remember to ink the rebar lengths into the cement to use as stakes for the PVC pipes.


3. If you are going with no cement slab, simply bang the rebar lengths into the ground. You want to space them no more than about 4 feet apart.


4. Slip one end of the PVC pipes over one rebar stake, and then bend the pipe and slip it over the paired rebar. This will form the pipes into semi-circles that make up the frame to hold the plastic sheeting. Once all the frames are in place, use more PVC piping to add strength to the frame by attaching pipes longways down the frame. One on each side and one on the top should do it.


5. Once the frame is up, it's time to get putting on the covering material. The easiest way to do this is by starting at one end of the tunnel and unrolling plastic as you go along - folding it over the ridge poles as you go to make sure it is watertight. Use screws and glue to secure it in place.


6. Finally, if you want to add a little extra ventilation to the tunnel then the best way is to cut some large holes in either end. If you are concerned about temperature or humidity control and want something a bit more sophisticated than just open ends, then there are plenty of options for small extractor fans that can be fitted into the walls at either end.


7. If you are wanting to add supplemental light, then run those extension cords out and fit out the lighting. If the supplemental light is to help keep the crop in the vegetative growth period then CFL bulbs will do just fine.

8. Best 3 Recommended Strains For Growing Autoflowering Cannabis

Wedding Glue Auto
5 out of 5
Easy grow and she wants to live calmag poisoned her and two others I was on to it quick she is super sticky starting week 9 time of photo
Verified customer
Reviewed 18 April 2022

Epic fruity hints with a strong vanilla background await you with our Wedding Glue Auto, a potent autoflowering hybrid with a staggering 26% THC.

Purple Punch Auto
4 out of 5
I rolled 3 joints for testing, tried them all, one each night, never finished more than a half joint because this shit’s strong
Verified customer
Reviewed 13 October 2022

An Autoflowering version of one of the most popular strains to hit the scene in recent years. An easy-to-grow hybrid perfect for beginners.

Strawberry Banana Auto
5 out of 5
And for me it’s the yields as I am a medical patient and consume a lot. I also appreciate that there’s not much tolerance build-up.
Verified customer
Reviewed 26 November 2022

One of the most potent autoflowering strains out there, with 27% THC,  a perfectly balanced XL producer, and terpene powerhouse.

9. In Conclusion

Given the right environment, growing autoflowering cannabis in a greenhouse can produce some elite buds. Thanks to extensive breeding, it is now possible to achieve excellent harvests all year long with the correct protocols in place. Between building a sturdy, south-facing greenhouse and knowing the ideal strain, the days of perpetual harvests are not far away and the ultimate way to recycle your organic living soil every time. So if you're having trouble growing autoflowering plants in a greenhouse, make sure you follow our tips for your best harvest yet!