5 Top Tips For Growing Autoflowering Cannabis Strains in a Greenhouse (2021)

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.
20 August 2021
6 min read
5 Top Tips For Growing Autoflowering Cannabis Strains in a Greenhouse (2021)

  • 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
  • 7. Best 3 recommended strains for growing autoflowering cannabis
  • 8. 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 themselves 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

Allows you to grow all year longCan be expensive
Better climate controlRequires a lot of space
Helps protect against pests and bugsEquipment 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 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.  

7. Best 3 Recommended Strains For Growing Autoflowering Cannabis

Wedding Glue Auto
5 out of 5
YESSSSS!!!! Just the cross I have been waiting for!!! This on eand the Mimosa Cake are gonna be strains of the year for me
Verified customer
Reviewed 13 April

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


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
4 out of 5
Delivery was a bit slow.... other than that I'm satisfied with the buying process. EVen got some freebies with my order which is always nice.
Verified customer
Reviewed 13 April

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

8. 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!



This post was most recently updated on August 20, 2021.

20 August 2021