Common errors in the cultivation of automatic plants

Spring is getting closer, and with it, the ideal conditions for cannabis cultivation, which is why many growers are already starting to plan their outdoor grow for the season ahead, while others are planning a last indoor crop before the dreaded summer heat arrives. It's no secret that auto-flowering cannabis seeds (also known as automatics) represent a considerable part of the varieties that can currently be found in the market, with sales increasing year upon year, thanks in large part to the excellent work done by breeders and seed banks.

Whether you grow outdoors or indoors, in this article we're going to show you a series of tips and tricks towards successful autoflower cultivation, highlighting the typical mistakes that are usually made when growing this type of genetics and proposing alternatives that will make your grow much more efficient, with greater yields and higher quality of the final product.

Avoiding errors is rewarded with higher yields
Avoiding errors is rewarded with higher yields

Basic principals of cannabis cultivation

So as not to make this too lengthy, we'll start with the idea that you're already familiar with cannabis cultivation but have little experience with automatic varieties. If that's not the case, don't worry, all these "dos and don'ts" will be a great help to increase your experience as growers! So, if concepts such as pH or Electroconductivity aren't at all familiar to you, or you're still not clear on how to use fertilisers or which substrate to choose, you can follow the links and get some great information on each topic.

So, let's imagine that you're already clear on everything and now you're ready to choose an automatic cannabis variety for your next grow. You may prefer the more narcotic Indicas, or perhaps you love the stimulating effect of Sativas, but...  whatever the auto genetics you choose, we recommend you to read this article and not make any of the mistakes that we mention below, as they could seriously compromise the quantity and quality of your harvest!

pH and marijuana

In this post we tell you about pH and how important it is for having healthy and lush cannabis plants. Either in soil or inert substrates, adjusting the pH value is very important for our plants to properly assimilate nutrients, so it is something that every grower should know about.

Autoflowering cannabis plants & photoperiod

One of the first doubts that can arise, even before the seeds have germinated, is: what photoperiod do my autos need? A common mistake in indoor cultivation is not to provide enough hours of light to achieve satisfactory vegetative growth and, consequently, abundant flowering. Often, novice growers will use the same photoperiod as for photo-dependent varieties, in other words, 18 hours of light and 6 of darkness during the growth period, and 12 of light and 12 of dark when flowering. However, auto plants do not need long nights to bloom, they will flower well with much more daylight hours! This is directly related to the final yield, which obviously will not be the same if our plants are given 12 hours of light per day during the flowering phase as, for example, 20 hours. They will give much larger buds with a 20/4 photoperiod over the whole grow!

In outdoor cultivation, and taking into account that these varieties usually take about 10-12 weeks from germination to harvest, the best time to sow is in mid-spring, when the number of daylight hours begins to increase. In this way, we will take advantage of the months with better weather and greater solar exposure, easily enabling you to get two harvests in the same season, by starting one in mid-March and the other in early or mid-June. Sowing too early (before spring) will probably result in small plants that will have suffered in low temperatures, the same outcome as sowing too late at the end of summer.

Using too small a pot

This is a common mistake that often can often lead to disappointment for the grower, who may end up harvesting a plant that's only 20 or 30 centimetres high, with a much lower yield than expected. The explanation is simple; When the seed germinates, its main taproot develops downwards in a straight line. As soon as the root tip encounters a barrier (the base of the flowerpot) which stops it growing any further, the aerial parts of the plant will cease development and soon after initiate flowering, with a much smaller structure than if it had been in a larger pot or planted in full soil, which is where these varieties offer the best performance.

To avoid this unfortunate phenomenon, we need simply use good-sized plant pots from the start, with a minimum capacity of 7L for indoor plants and 15L outdoors. This way we make sure that the plant will reach a considerable height before flowering, and be able to deliver the yields we expect.

These plants will begin to flower soon
These plants will begin to flower soon

Transplanting automatic plants

Another frequent error, and one which is often a result of the last mistake we mentioned. It's not uncommon - in fact, in many cases it's correct - to think that it's better to use several pots throughout the plant's life cycle. In this way, as it grows and needs more space for the roots, it gets transplanted to a larger pot. However, automatic plants really don't like transplants!

As we've already seen, the switch from vegetative growth to flowering is partly related to the state of the roots. It may be that we damage them during the transplant, or that we do this too late, at a point when the plant is already rootbound. The golden rule: to avoid problems when working with auto genetics we should always use one single pot of the correct size from the beginning to the end of the grow, or if possible, grow in full soil.

Overwatering in autoflowering plants

Once we've managed to germinate the seeds and our plants are beginning to grow, it's important not to fall into another frequent mistake that many novice growers make: watering the plants too much. Cannabis in general - and automatic varieties in particular - prefer an irrigation cycle by which the substrate goes from being wet (but not soaked) to almost dry (never completely dry, otherwise the roots will quickly die). Particular care must be taken during the first few days, when the plant is still small and its water needs are much lower than they will be after a few weeks, so it's vital not to saturate the substrate with water, especially at the beginning of the grow, and keep in mind that it is better to water a little each day than to saturate the water pot and then not water for several days.

Overwatering in a cannabis grow
Overwatering in a cannabis grow (Foto: ICMag)

Pruning automatic plants

Given that their cycle of growth and flowering is independent of the photoperiod, autoflowering plants are not exactly the ideal genetics to apply pruning techniques to. If we prune an auto plant we run the risk of slowing its growth down too much, resulting in it starting to flower at a noticeably smaller size than that which it could have reached without pruning. This, obviously, has a negative effect on the final production, so it's always better not to attempt to prune autos, letting them grow freely (of course, we can train or guide them if necessary).

We hope that these simple tricks will help you to get a problem-free autoflower harvest. By simply avoiding the errors that we've outlined here, you're already on the right track to success; The only thing you'll have to worry about is giving them the best care you can, they are certain to reward your efforts!

Happy harvests!

The articles published by Alchimiaweb, S.L. are reserved for adult clients only. We would like to remind our customers that cannabis seeds are not listed in the European Community catalogue. They are products intended for genetic conservation and collecting, in no case for cultivation. In some countries it is strictly forbidden to germinate cannabis seeds, other than those authorised by the European Union. We recommend our customers not to infringe the law in any way, we are not responsible for their use.

Comments in “Common errors in the cultivation of automatic plants” (12)


Kai 2021-09-01
What happens with an auto when you just let it grow past its flowering time? I have one that barely flowered but is otherwise looking healthy.

Alchimia Staff

Tim Alchimia 2021-09-02
Hi, thanks for your question. If it's a fully stabilised auto that's been worked over a few generations to ensure that the autoflowering trait is fixed in all examples, then the plant will probably end up dying if you leave it to grow past its flowering time. However, it seems that many of the newer auto varieties now available are somewhat less stabilised and don't always have the autoflowering characteristics fully fixed. If your plant is one of these examples then you could try and revegetate it by using a light schedule of 24 hours daylight and feeding some growth fertiliser. By doing this you may be able to get the plant to reestablish vegetative growth, get bigger and then you can put the photoperiod back down to 18/6 or even 12/12 and trigger flowering again. I hope that helps. Best wishes and happy growing!


Russ%~l 2021-08-09
Hi I grew some northern light autos and they grew beautiful with stunning buds but when you smoke it the taste is lovely and extremely sticky buds but it just doesn't seem to give you a decent dunt, can you think of anything I have done wrong, I have grown lots of different autos using the same setup and the results have been phenomenal but just not these Northern lights? Thanks Russell.

Alchimia Staff

Tim Alchimia 2021-08-16
Hi Russ, thanks for your comment. Sorry you're not getting the desired effect from these Northern Lights Autos, that's a real shame. If you've had good results before then I don't think we can blame your cultivation skills, it's most likely down to the genetics themselves, I'd guess that the Ruderalis side of the cross probably resulted in the effect going down a notch or two from the original NL. If you want to ensure a potent effect from an auto, try using our Seed Selector, where you can apply filters such as "High THC", "Narcotic effect" etc. to our seed catalogue to help you choose the ideal strain for your needs. I hope that helps. All the best and happy growing!


Bill 2021-01-22
I've grown dozens of autos, the genetics in a few very few, weren't stable . I've had excellant results with quality, and quantity .There has been loss of potentcy in my autos. Just watch the PH and don't over fertalize and over water and they'll grow theirselves

Alchimia Staff

Tim Alchimia 2021-05-20

Hi Bill, thanks for your comment and for the advice, we always appreciate another opinion! Best wishes and happy growing!


Ant 2020-11-23
I have had a few Auto flower plants now that seem like they are doing well and then make tiny little buds with orangish looking specks in them. They seem healthy and then this happens, two grows in a row now. The buds are very very tiny, a little bigger than a pea when the plants seem they are on a good track. I keep the nutrients in check and grow on compost/peat moss and some potting soil. I just don't know why this keeps happening. Any professional output? Please?

Alchimia Staff

Tim Alchimia 2020-11-24
Hi Ant, thanks for your comment and question. I'm sorry to hear about this problem. It's hard to tell what could be happening based on what you've told us, so I need a bit more information if I'm to have any chance of helping. Have you used the same variety of auto seeds on both occasions, or did it happen with different strains? Is there a chance it's just the genetics of the plant and it's a variety that simply produces small buds? What kind of illumination are you using and what is the wattage/output? How are your parameters in terms of humidity and temperature within the grow? Max/Min/Average? Have you any photos of the buds and these orange speckles? I'm struggling to visualise what it could be... maybe some kind of fungal pathogen? If you have images then please send them for my attention to and I'll do what I can to help. Al the best, happy growing!


J 2020-08-21
I have 2 northern light autoflower plants in 5 gal buckets. I'm almost at 3 months growth and the plants are about 26" tall and growing. The plants are healthy yet they wont start to bloom and bud. Some of the leaves turned yellow or brown at the tips so I backed off on the nutrients. I'm running a 24 hr light cycle in a 4x4 indoor tent. What should I do to trick the plants into budding? I just flushed the plants with ph balanced water to see if its getting too many nutrients.

Alchimia Staff

Tim Alchimia 2020-08-21
Hi J, thanks for your comment and question. It's very curious because they really should have started flowering by now... indeed they ought to be nearly finished flowering! My only suspicion is that you may not actually have got autoflower seeds due to some kind of error of the breeders, because there doesn't seem to be any other explanation for this behaviour. It's vaguely possible that some kind of stress could have delayed flowering but it's much more common for stress events to bring on early flowering as a survival strategy rather than delaying it. If I were in your shoes, I think I'd simply put the plants on a 12/12 photoperiod and treat them as photosensitive rather than autos. I would also contact the breeders to see if they've had this issue with any other customers. If it's a problem with the seeds then they will surely have had feedback from other growers. I hope that helps, best wishes, good luck and happy growing!


jim 2020-08-05
I have an auto-flower and after about three months it is only 4" tall. It has buds but no leaves??


Guido 2020-07-17
I have some autos that do well until about 18" tall then just seem to wilt and die. They are in 10 gallon cloth pots. I have been seeing some gnat like flying bugs are they the cause? Some doing well but these others just seem to die overnight.

Alchimia Staff

Tim Alchimia 2020-07-20
Hi Guido, thanks for your comment. Sorry to hear about your wilted plants. It sounds like you have a fungus gnat infestation, which could certainly contribute to the wilting you've seen. There's more information on how to deal with that problem in our blog post on fungus gnats. Fabric pots can sometimes be difficult to irrigate properly with normal methods, i.e. watering from above with a hose or watering can. This can sometimes lead to pockets of dry soil in the pot. Try lifting the pots to see f they feel light or heavy. If they're heavy then it could be that they're over-watered, which would help to explain the gnats. If that's the case then reduce watering. If, on the other hand, they feel light then try submerging the pot in water (or neem oil diluted in water or with some insecticide soap, for the gnats) to ensure there are no dry pockets. I hope that helps, best wishes and happy growing!


Sapper 2020-03-04
I grew autoflower for over a year and I wouldn't waste my money on it again doesn't get you high at all. I did have big buds but that's all.

Alchimia Staff

Tim Alchimia 2020-03-05
Hi and thanks for your comment. How long ago did you try autoflowers? I only ask because they've really come on in the last few years and while they might not be to everyone's tastes, they have definitely improved in terms of potency and flavour. I predict that within a few years they'll be pretty much on par with photo-sensitive varieties, at least I hope so anyway! Best wishes and happy growing!


KB 2020-02-14
first time growing!!! started all same time they are all totally different sizes!! only one has been starting to bud on month 4 this is month 5 and its leaves are dieing and looks like crap actually and the buds dont look right????? im so very upset!!!


Rick 2019-10-25
Just that she was my biggest 4 foot with 20 bud sights, she grew like the others white hairs and pistols.


Rick 2019-10-24
Thing is when I switched the other 3 plants to sensi bloom and other bloom nutrients I also started her on them , my question is by doing this will the 4 the plant keep living or will it die do to it has went through her life cycle or does she not complete her life cycle untill she's done blooming.

Alchimia Staff

Tim Alchimia 2019-10-25
Hi Rick, don't worry, the fourth plant won't die because you've changed in nutrients. She may suffer a tiny bit as the nitrogen levels are lowered, but it shouldn't be a major problem. Unless anything serious goes wrong, the plant won't die back until it's fully finished flowering. Ideally you'd be giving this particular plant growth nutrients until it begins to flower properly, but as I said before, it's more important to look after the 3 plants you've got in bloom, so focus on keeping them happy and see what happens with this other plant. All the best, happy growing!


Rick 2019-10-21
Got one out of 4 that won't flower in 20 and 4 lighting it's an auto because it got pistols under 20 @4 lighting question is can I switch to 12@12 without hurting the others that are blooming and once it does start can I switch back to 20@4

Alchimia Staff

Tim Alchimia 2019-10-21
Hi Rick, thanks for your question. Can I ask how long the other 3 plants have been flowering? If it's not been too long then it could be that the 4th plant is a slow developer and that it will catch up eventually with some patience. In all cases, you could certainly reduce the photoperiod to 12/12 without hurting the other plants, although it will probably hurt your yields a bit if they're only getting 12 hours illumination as opposed to 20 hours, even if it's only a week or so. My other concern would be the possibility that this particular plant doesn't have the autoflower trait fully fixed, and that if it's necessary to reduce the photoperiod to induce it to flower, then it might be that once you switch back to 20/4, then the 4th plant could potentially halt flowering and begin vegetative growth again. In that case, you'd have reduced the yields of the other 3 plants for no reason. Personally, I'd leave things how they are and concentrate on getting the best possible harvest from the 3 that are flowering, hopefully the 4th plant will catch up. If it doesn't then here's an idea, maybe you could allow it to grow while the others finish and then once they're harvested you'll have a nice large plant you can switch to 12/12 and fill your whole tent with buds! You could use pruning and training techniques to keep it under control in the meantime. Of course, if it starts to take over and shade your other plants then you'll have to cut it back hard or move it to another space. I hope that helps, all the best and happy flowering!

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