Growing autoflowering cannabis

Start of flowering
Start of flowering

Autoflowering cannabis is on the rise. A lot of growers - whether because of plant size, growth speed or ease of cultivation - grow autoflowering marijuana during the outdoor season, in addition to growing regular or feminized marijuana plants.

How to grow autoflowering marijuana plants

Here we will try to show you the best way to grow autoflowering plants, so you get the best quality and yield out of your plants. Mikromachine from Kannabia seeds was used in this crop, grown in 18 and 11 litre pots. They were grown in Biobizz Allmix soil, which already contains the necessary nutrients for the first weeks of life of our plants, so we don't have to worry about the overall nutrition of the plants.

Mikromachine 2 starts its blooming stage
Mikromachine 2 starts its blooming stage

It is important to ensure that, during the first phase of its life, the plant is neither overfertilised nor overwatered, as it can have a very negative impact on our autoflowering plants. This kind of stress on plants will result in their growth period being seriously affected, not developing as much as they should.

When you start your crop, the first step is planting the seeds in jiffy pellets. Once they have germinated and grown (when they become a seedling), transplant them to a 18 litre pot, which is especially designed for autoflowering plants, being taller than wider.

It is important to take into account the shape of the pot. Autoflowering cannabis can grow more or less depending on its cultivation. Autoflowering marijuana plants have limited growth due to several factors, the most important being the autoflowering gene that makes them flower when they have reached sexual maturity.

However, this gene is activated by some factors that make plants to reach it more or less quickly. The most important factor to consider is the amount of substrate used to grow autoflowering cannabis, and how it is distributed on the plants. It is important to stress that autoflowering plants start flowering when their roots reach the bottom of the pot. The longer it takes for the root of the plant to reach the end of the pot, the taller the plant will be, so you will get a higher yield.

Materials needed for the cultivation:

Three week into flowering
Three weeks into flowering

Start of growth period

To get started, we germinated Micromachine and Speedy Gonzales seeds from Kannabia, planting them directly in 18 litre pots. These pots, as explained before, are deeper than wider so they are ideal for growing autoflowering cannabis. We used quality soil containing enough fertiliser for the entire crop, so that liquid fertilisers were not needed.

The growth period of these plants is very limited, from 2 to 3-4 weeks inluding the stretching period (growth after flowering). However, their growth can vary widely depending on how the plants have been grown.

At the beginning of the growing period, when plants were still very small, they were watered using a small amount of water, no more than 330 ml per pot and plant, using a nutrient solution consisting of:  1.5 ml/10 litres Regulator,  1 ml/l Naturcannabis growth, 2.5 ml/10 litres Startbooster,  8 ml/10 litres Amino Roots, Trichoderma Hazarium, 1 ml/l CALGreen.

Watering was done using the same amount of nutrient solution for much of the growth period. This has a positive impact on the root growth of plants leading to a better development of the aerial part of the autoflowering cannabis plants. Over the first week of life, the plants are all well sized.

Four weeks into flowering
Four weeks into flowering

After one week, the rootball gets bigger and the plant can absorb more nutrients than before, so you will be able to slightly increase the amount of nutrient solution, from 330 ml every other day to 500 ml, using exactly the same dosages.

Their growth is regular and we can observe how plants grow a few inches every day during their vegetative period, which turns them into bigger, stronger and more robust plants. After these two weeks - during which watering is controlled so that roots expand better - we clearly notice the effect of this. Plants grow solidly and gracefully, and will be ready to enter the flowering period with a good structure for an abundant bud yield.

Flowering period of Mikromachine by Kannabia

The flowering period of autoflowering plants is much shorter than in regular cannabis, as the former only require about a month and a half or two months (at most) to complete the flowering period, from the germination of the seeds. In some cases, and depending on the crops, flowering can be shorter or longer. It basically depends on the strain and the environmental conditions during cultivation.

Mikromachine secondary bud
Mikromachine secondary bud

In this case, plants were grown during late June, July and August, when high temperatures and the strong sun help to create ideal growing conditions for autoflowering plants. This is both due to warm temperatures - that help the plant's growth - and the long sunny days with low rainfall, typical of this season.

Once flowering has started, we can observe how the plants have a good structure that will allow them to produce big and thick high quality buds, as well as excellent yields. As we can see from the pictures, the plant structure is very similar in all individuals, but it's worth mentioning that you will later be able to distinguish two different genotypes.

The final height is around 80-90 cm, with a short internodal distance partly due to the additives used: Aptus Regulator, which makes plants more drought-resistant, also increasing significantly the cell wall and the internal stem diameter, thus reducing internode distances.

During the first week of flowering, by the end of the stretching period, you can easily see the first flowers on the tips of the branches. As weeks go by, we will increase the fertilizer dosage so plants have enough nutrients to prevent any stress caused by a deficiency or excess of nutrients.

6-7 weeks into flowering
6-7 weeks into flowering

It is important to monitor the levels of nitrogen present in fertilizers to prevent cannabis plants from an excess of this element, for they would produce lanky buds at the beginning of flowering. If this happens, flush the roots so that EC levels in the pot are appropriate for each stage of the plant's life.

As you can see in the pictures, two plants are darker than the other two. In this respect, it is always better to feed our plants individually - according to their needs - in order to get the best possible quality.

If you want to water all your plants from the same tank, we recommend you to pay attention first to those plants that need more nutrients, so you prepare the appropriate nutrient solution into the tank, water the plants with more nutritional needs, and then dilute it with water, lowering the concentration of EC in the nutrient solution, and thus providing each plant with the right amount of nutrients, which are essential for optimal results.

Week 4 into flowering

At the 4th week of flowering we can see how the flowers constantly gain weight, free from any pest that may affect their quality or yield. At the beginning of flowering, a small red spider infestation occurred, which was trated with Cinnaprot. This product and some neem oil leaved the plants free from any pest before flowering, protecting them from any other unwanted visitors.

The nutrient levels increase this week, according to the Aptus feeding schedule:

Aptus feeding schedule
Aptus feeding schedule

At week 5 of flowering, buds are well formed and ready to show their spectacular resin coat, full of THC. Flowers are compacting in all plants, regardless of phenotype. During this week, raise a little bit the nutrient concentration, for plants need to be loaded with nutrients in order to have enough food reserves to develop fat compact buds with the best possible organoleptic properties.

Continue adding flowering additives like Aptus Topbooster and Regulator until the last week of flowering, since humic and fulvic acids (and other acids) help the plants' buds ripening.

End of flowering in autoflowering cannabis

Mikromachine at the end of flowering
Mikromachine at the end of flowering

At week 6, one week before the last week of flowering, you should observe the trichome morphology to determine its maturity. Depending on how you see the trichomes through a 50 x magnifier glass, you can harvest the plant or wait a few days until it is fully ripe.

In this case, the Mikromachine strain needed 80 days from germination to harvest. During the last week, roots were flushed in order to reduce the concentration of nutrients in the substrate and to force plants to take nutrients from their own reserves, thus getting the best flavour and smell.

At week 7, the last week of flowering, you will clearly see how the buds are ripe. Many plants have the same bud colour, which has turned brown/orange, showing clear signs of maturity. You should check the trichomes again before harvesting your marijuana plants.

Throughout the flowering period, these plants have been victims of a bug that neem oil can't get rid of. We are talking about the fearsome caterpillars. They come from butterflies that lay eggs on the leafs. In ideal conditions, in this case around mid-August, when there is high humidity due to constant rain, we can observe this devastating specimen, the caterpillar.

Mikromachine's central bud at the end of flowering
Mikromachine's central bud at the end of flowering

As the pest appeared at the end of flowering, caterpillars were hand picked. Keep in mind that, when using any product that could leave traces on the buds, you should harvest your plants at least 15 days after any product application, for the flavour would be significantly altered and therefore not suitable for consumption.

After harvesting, the plants were dried in a drying tent with a carbon filter and an extractor to prevent any smell. When harvesting, the plant moves and the terpenes come off creating a coffee shop atmosphere. You can get rid of the smell by using filters or other effective devices like the Neutralizer .

Mikromachine's resin glands
Mikromachine's resin glands

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.
2014-11-17 Cannabis grow guide

Comments in “Growing autoflowering cannabis” (7)


Go-with-the-autoflow 2022-07-13
Hello! I have choosen to grow the Auto Dos Si Dos(feminized) for the for the first time. Because it's just a hobby of mine i got a 120x120x220 cm Budbox tent where my four plants are growing atm. I have been using (allways) a 600W HPS- light with the adapter so i can ajust the power from 250W-400W-600W-650W. What really makes me wonder is how come this specific strain flowers/blooms like a dream even after my cooler (by cooler i dont mean a fan, this thing cost 850€) broke and the temperature inside the tent is +40C° daily? Sure i have been giving my plants a lot's of water (1500ml twice a week/plant + all the nutrients) but i've grown strains that would 100% show signs of "sickness" even on +30-35 Celsius so it makes me wonder - is this some kind of a superbreed? I'm going on the fifth week of flowering and the buds look lovely. In the growing manual (that they gave to me when i bought the seeds from the store) was a warrning about this strains low capabulity of handeling stress and it was strongly recommended not to even cut off the leaf's that are blocking light from the buds and the optimal temperature would be around +22-25C°. I sure did cut the extra leafs from blocking the light(as i have done for 15 yrs. to all my autoflowers i have been growing). I grow these plants in mold - like i have done every single time in my life. Also i did cut a scion from one of the four plants with a great succsess and i pinched one of the plants as an experiment (which was not recommended on autoflowering plants) and it went really well. Sure i have studied a degree on gardening but growing tomatos has nothing to do with this :) This Auto Dos Si Dos is really fast growing; just 75 days from planting to harvesting. Its "genetics" are ⅓sativa ⅔indica hybrid and its a mixture of Girl Scout cookies X Face Off OG Cush crossed with Super Auto #1 From all these different herbal plants i have grown this seems to be the most easy and fast to grow. Compared to all these time taking strains such as Lemon Tree and White widow for example this looks likebthe fastest way to get 100g (dry) buds per plant. After two weeks i'll know entirely the specifics about the plants "influence" and it's taste etc. But what i'm saying is that this might be a superbreed that is allmost impossible to fu*k up for a beginner (indoors) and it grows so fast you can harvest while the cops are driving to your house (if you happen to live in a place where growing a plant is a crime).

Alchimia Staff

Tim Alchimia 2022-07-13
Hi and thanks for the comment! We're really happy that you're enjoying the results from these seeds and that the Auto Do-Si-Dos is outstripping expectations in terms of performance, that's just great! It sounds like you're dealing with some seriously high temperatures in your tent, have you thought about upgrading your lighting from the HPS lamp to LED grow lights? LED technology has evolved so much during the last few years that almost all the growers I know who used to use 600w HPS have switched to 600w Zeus Lumatek and they're all really happy with the yields, flower and resin quality but most importantly, the reduction in temperatures which makes it possible for them to keep growing indoors all year round without needing to pause in summer due to the heat. Just a suggestion to help control the high temps! Thanks again for your comment, best wishes and happy growing!


Jack Roberts 2019-10-26 has some of the best grow lights for autoflowers. REDSPEC grow lights and the brand new LM301H samsung diodes.


Sergey Is an Alchimia client 2019-03-28
Hi there. I would like to grow in the 20L Fabric pot. Use Organic Classic soil (Coco Coir, Worm Castings, Compost, Perlite (10%), Vermiculite, Volcanic Rock Dust, Bone Meal, Gypsum, Fermented probiotic bran, Organic nutrients) I prefer to use Biobizz Grow Bloom and FishMix. Auto seeds like this organics style? Do you have any special advice?Thanks. Kind regards.

Alchimia Staff

Tim Alchimia 2019-04-08
Hi Sergey, thanks for your question. That soil mix sounds great, but automatic plants don't have the same nutrient requirements as photoperiod plants, so you'll probably have to make it a little less "hot" than normal and pay particular attention to the drainage, the worst thing that can happen to an auto is to become water-logged. With that in mind, water the 20l pot sparingly until the roots have colonised the substrate, taking care not to saturate the substrate too much. Hope that helps, all the best and happy growing!


Robert Murphy 2016-11-13
I'm a newbie who has been reading a lot there's a lot of confusion I'm about finish gettin all i need to start my 1st grow i want to grow some autos but readin so much I'm confused about how to get it started correctly some people say i need this and others say that i need that here's how i want to set up grow tent 4x4x5 root maker 5 gallon fabric bags 2 1000 watt led lights and a 6 inch inline fan with odor scrubber(question is an exhaust fan need when using an inline fan or are they the same????) i was thinkin of using sub cool's super soil which i saw in 5 pound bags(how much soil should be placed in a 5 gal container for a nice grow????) I read that super is not good for seedlings and i wanted to plant the seed straight to the soils so that i don't have to transplant read autos don't like that so i was thinking about placing some black gold seedling mix over the super soil would that be a good thin to do???? i was also thinking of jiffy peat pellets but again transplanting Ireally need help with this matter any advice would be really appericated.... Thank You........

Alchimia Staff

Dani Alchimia 2016-11-14
Hi Robert, First of all, autos hate transplants. The ideal would be starting your seeds in the definitive container (which should be around 3 gallon, autos don't usually take profit from bigger containers). You can germinate in jiffy pellets, but put them in the container as soon as the seedlings sprout. Normally, an air extractor is used along with the carbon filter to drive the air inside the grow tent out. Another extractor of lower capacity is used to put fresh air inside the tent. Here you have a nice post on ventilation of indoor grow spaces. About nutrients and growing media: coco coir improves the texture of most soils and has very few nutrients, so you could mix some coir with your supersoil to make it a bit less strong for your plants. Hope it helped!


Ben_91 2015-12-17
Hey, great article although I have a question that is rarely if ever addressed online in autogrow journals. Basically I intend to grow a bunch of autos next year but I plan on putting them straight into the ground as opposed to growing them in pots. I will initially start them off in party sized cups/pots following germination, and before the seedlings become root bound (10-14 days) I will transfer them straight into the ground in an open field where they will receive 18+ hours of direct sunshine a day at this time of year (May/June) at 51N. I haven't got the space, money or time to be dealing with large pots which is why they are going in the ground. I know this will work still but what are the side effects? An increased finishing time? Any kind of stress? Thanks!

Alchimia Staff

Dani Alchimia 2015-12-22
Hi Ben_91, Sorry for the late reply, something happened and my post was never showed. There is not problem at all, if you grow your autoflowering strains directly in the ground. Actually, if the substrate is good your plants will grow bigger and yield better. Basically, when you grow your plants in the ground you have two main disadvantages: on one hand, you depend on the quality of the substrate (you can always dig a hole and fill it with quality soil). On the other hand, you can't move your plants (many people put the plants inside at night to avoid thieves). If you start your autos in pots, never let the main root reach the bottom of the pot, try to transplant them earlier. Hope it helped! ;)


Papa Indica 2015-07-24
Impressive looking trichome production.

Alchimia Staff

Dani Alchimia 2015-07-27
Hi papa Indica, Breeders have really made a great job with autoflowering strains, these girls have nothing to do with their older sisters from years ago. Auto hybrids developed today are much better in all aspects than old autos, since instead of using Ruderalis lines today we can use quality automatic hybrids to develop new crosses with photoperiod strains. All the best!


Peer Sorensen 2015-06-08
Hey. When it's auto flowers is giffis then the best or better without? Thank you.

Alchimia Staff

Dani Alchimia 2015-06-09
Hi Peer, There's no need to use jiffis, you can germinate your seed and once it has sprouted plant it in the definitive container. Best vibes!

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