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best soil for autoflower cannabis seedlings seeds

Growers can supplement their soil with predatory nematodes that feed on these invaders and reduce their numbers within the rhizome.

During the seedling phase, your autoflowering plants won’t need any nutrients. Growers can start supplementing with nutrients about 2 weeks into the grow, but should do so lightly to avoid damaging the crop.

Autoflowering cannabis strains are known to be hardy and easy to grow. Despite their low-maintenance and photo-independent nature, they can still benefit from optimised soil and nutrients to reach maximum yield and quality.


Another microorganism that will benefit the soil of your autoflowering plants are mycorrhizal fungi. These type of fungi form a symbiotic relationship with the roots of your plants. The roots of cannabis plants produce exudates, a variety of excretions including sugars. Beneficial fungi attach to the roots and feed off these sugars. In return, they act as an extension of the root system, reaching out over a greater surface area than the plant could achieve alone, ferrying in nutrients from afar.

The soil that your autoflowering plants are growing in isn’t merely a medium that the roots sit in while the plant grows—it’s much more than this. The soil is a diverse and thriving web of life that includes symbiotic organisms and pests alike.

Whether you are cultivating your plants indoors within a grow room or tent, or outdoors within greenhouses or garden beds, your soil can be supplemented with beneficial microorganisms.

Even during the flowering phase, autoflowering varieties don’t need a huge amount of extra food. Bloom nutrients and boosters can still be applied, but with a less-is-more approach. Pay close attention to your crop and apply when you deem necessary.

Worm castings are a type of organic fertiliser that, when mixed with soil in the growing pots, provides the plants with all the nutrients they need from start to finish. Worm castings originate from worm excrement and contain all the nutrients necessary for optimum growth. The main difference between the two types of fertilisers is that there’s no problem if you add worm castings in excess, whereas if you overdo it with super soil, the overfertilisation will end up burning the plants.

Pot size can range between 11 and 17 litres. The bigger the pot, the bigger the resulting plant. As the growth phase of autos doesn’t usually exceed 30 days, we don’t recommend using bigger pots than these as the plants’ short vegetative period won’t allow them to make the most of the extra substrate. Therefore, a pot smaller than 20 litres will be more than enough. Below you can find the different ratios for the different substrate components:

Even though not all autoflowering strains are the same, the best soil for them is usually light, nutrient-free, and not very compact. Autos don’t normally like lots of fertilisers, although you can’t compare, for instance, a Moby Dick XXL Auto (a heavy yielder and therefore a rather greedy plant) with a Bubba Kush Auto (a strain that needs much less fertilisation).

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Autoflowering cannabis strains require aerated soils for optimum root oxygenation. Using pots with holes on the sides is always a good choice. You’ll also need to add perlite or coco coir to facilitate aeration and prevent the soil from becoming compacted. In this post we’ll tell you the best ratio of all these elements, and we’ll also recommend a recipe for making the perfect soil for your automatic plants.

Irrigation control is imperative for the optimum development of autoflowering plants. If you provide them with too much water, they won’t grow because they hate excess moisture. Hence the importance of watering them more frequently but in smaller quantities. We recommend watering them every other day during the vegetative period, so their roots can expand and grow in search of moisture, thus developing perfectly. And they have sufficient oxygen when they’re not wet, because they only find oxygen when there’s no water.

Autoflowering strains flower automatically from the 30th day after seed germination, regardless of the photoperiod that they’re exposed to. Their full life cycle lasts between 2 and 3 months. These strains are easier to grow than their feminised sisters due to their speed and the fact that they’re not photo-dependent. But for their cultivation to remain easy, they require the right type of substrate, and this needs to be maintained during the whole growing process. Their short life cycle leaves little room for error; hence the importance of making as few mistakes as possible. In this post we give you a substrate recipe so that you don’t need to add liquid fertilisers to your grow; this way you’ll only need to feed your plants with water.

In contrast with the feminised strains (whose growth time is predetermined by the changes in the photoperiod), the growth phase of the autoflowering strains is predetermined by their genes: this means that they’ll start blooming from their second month of life regardless of the photoperiod that they’re exposed to. This is why it’s so important to make the most of the first month of growth, keeping the soil well aerated at all times. If the soil becomes waterlogged, the plants could stop growing due to the excess of moisture.

Last time we found how to find the perfect pot size for autoflowering plants and now we need to see what to put in those pots.

This means that you should look for a growing medium that is airy, but if you can’t get a hold of such a thing then ad some Perlite to increase the water drainage and root penetration.

Light or heavy

Second thing that affects your plant is the nutrients that are in the soil.
Soilless mixes usually have almost no nutrients and you will need to ad them with fertilizers during the growth of the plant.

First thing you need to know before buying your growing medium is – autoflower plants love to grow in “airy” growing medium. Airy means that the growing medium should be very spongy and allow the root mass to penetrate it well. If the soil is not “light” enough then the roots will struggle to penetrate the ground and that will stress your plant. Heavy soil will also stress autoflower plants by not allowing the roots to get enough oxygen and not allowing the water to penetrate the soil, leaving some dry spots in the middle. If the growing mix is too “light” then roots won’t be able to hold, support the plant and it will easily roll over. Too light soil will also struggle to hold water and will dry up in short amount of time.

Soil in other hand will always have some amount of nutrient in it and you need to check the package to see what they are and how long can a plant live only on nutrient that are in the growing medium. Usually commercial potting soil contains all the necessary nutrient and they are time released so that when your plant needs them they will become available. These mixes are very different and you need to check the label on each of them but in general a soil that contains these necessary elements like Nitrogen, Potassium and Phosphorus will be able to support and feed your plant for the first 3 to 5 weeks and you won’t need to add additional fertilized in that time period.