best soil for autoflowering seeds

The Best Soil For Growing Autoflowering Cannabis

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.

Autoflowering cannabis strains are known as the easy option when it comes to cultivating the herb. Their hardy nature, fast growth, and ability to flower without a change in photoperiod make them a prime choice for both beginner and advanced growers alike. These sturdy strains often require little maintenance and allow sufficient room for error; however, when chasing the optimal yield and bud quality, a few boxes need to be checked. One such box is adequate soil.

Autoflowering strains contain genetics from Cannabis ruderalis, a subspecies that evolved and adapted to extreme weather and light cycles far into the Northern Hemisphere. Such adaptations and the resulting hardy nature of autoflowering strains mean that they aren’t too picky about soil. However, to encourage them to reach their true potential, an optimal soil mix should be applied.


Autoflowering strains favour light and airy soil with less nutrients than photoperiod strains would prefer. It’s best to make your own soil mix as opposed to purchasing a ready-made mix from stores, as they may be too high in nutrients like nitrogen.

Heavy potting soil will stress autoflowering varieties, preventing their roots from accessing adequate amounts of air. Roots may also have a difficult time penetrating and growing through a heavy medium.

This basic recipe offers a soil mix that contains adequate nutrients, as well as materials that will help to boost the aeration of the soil medium.

  • 3 parts peat moss
  • 3 parts compost
  • 2 parts perlite, pre-wet
  • 1 part vermiculite, pre-wet


Autoflowering strains are usually short and compact, a genetic trait stemming from the ruderalis subspecies. This characteristic, along with their rapid growth times, means that autoflowering strains don’t actually need that many additional nutrients.

Most autos will only stay in the vegetative phase for a short period of time, meaning they won’t require a huge amount of veg nutrients like nitrogen. Adding too much can actually burn autoflowering strains, so feed them conservatively.

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.

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.


The pH scale is a measurement of how acidic or alkaline a substance is. The scale features 14 readings, with 7 being neutral, numbers lower than 7 being acidic, and numbers over 7 being alkaline. Soil can vary in pH, with differents plants thriving in varying levels. Autoflowering strains are similar to photoperiod varieties in that they prefer a slightly acidic soil medium.

Growers should try to keep their soil within an optimal pH range of 6.2–6.5. If purchasing soil, make sure the product is suitable in terms of acidity. If you need to regulate the pH of your soil, there are numerous products available to achieve this.


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.

As all growers will know, especially those who raise their crop in the great outdoors, there are many pests out there with an appetite for fresh cannabis leaves, roots, stems, and flowers. These critters take many forms, and lots of them reside within the soil. Parasitic nematodes can be a problem, eating cannabis roots from both the insides and outsides.

Autoflowering cannabis strains have different soil requirements in comparison to their photoperiod counterparts, preferring light and airy media.

The Best Soil For Autoflowering Cannabis Plants

Published : Aug 9, 2019
Categories : Cannabis cultivation

Autoflowering strains attract many cultivators due to their rapid growth and small, easy-to-manage structures. If you’re planning to grow an autoflowering variety, use this soil mix for optimal results.

There are quite a few differences between autoflowering and photoperiodic strains, the most notable of which being that the former initiates flowering without a change in light cycle. Autoflowering strains received this unique trait from a cannabis subspecies named ruderalis, which evolved in the colder climates of Central and North Asia, experiencing endless summer days and long winter nights. This subspecies has since been crossed with many sativa and indica strains to create legions of popular hybrids.

As well as having the unique autoflowering trait, these varieties have different needs and demands compared to standard photoperiodic strains, including the type of soil they require to thrive. Their hardy nature allows them to tolerate poor soils and harsh environments, but providing them with high-quality soil and nutrients in the right quantities will result in superior yields.


It’s true that most autoflowering plants can tolerate heavier soils, but they much prefer a substrate that is light and airy. When cultivated within such a growing medium, the roots of autoflowering strains can easily penetrate the soil, where they anchor the plant securely in place, mine for nutrients and water, and intake oxygen. By using light soil, you’ll be providing your plant with a perfect foundation for healthy growth. This kind of medium also allows for good water drainage, which can help to prevent detrimental conditions such as root rot.

An ideal potting mix for autoflowering strains should include peat moss, a substance that is harvested from peat bogs and is formed from decomposed moss. Another primary ingredient in autoflowering soil is compost, a resource that can easily be made at home by composting waste organic matter such as kitchen scraps. Secondary ingredients in the potting mix should include perlite, which is an amorphous volcanic glass that helps create space in soil to increase drainage and aeration. Vermiculite is another key ingredient that provides aeration to the substrate.

These ingredients should be mixed using the following formula:

3 parts peat moss
3 parts compost
2 parts perlite
1 part vermiculite

It can be cheaper to make your own autoflowering potting mix when buying these ingredients in bulk. However, if you don’t have the time, you can purchase premixed soil.


Autoflowering strains have also earned their hardy reputation due to the fact that they can put up with little food. In fact, it’s very easy to overfeed autoflowers and damage them by doing so. Autoflowering strains are usually significantly smaller than their photoperiodic counterparts and therefore require much less feeding during their life cycle. Feed them very lightly, and be particularly careful of nitrogen levels during the vegetative phase. Many premixed soils will come with the correct levels of nutrients, and will often provide enough for plants to survive for multiple weeks. After this, add fertiliser sparingly.

A good addition to autoflowering soil are mycorrhizal fungi. Although these life forms aren’t nutrients, they do help plant roots by breaking down organic matter into small and usable molecules and transporting them into the root system. Introduce these into the soil to assist your plant in making the most out of the potting mix.


The pH scale is a tool used to measure the acidity or alkalinity of a solution. All soil has a particular pH, which can be tested using probes or paper test strips. The pH scale ranges from 1 to 14, with 1–6 indicating acidity, 7 indicating neutral, and 8–14 indicating alkalinity. All cannabis plants have a preference for slightly acidic soils within the range of 6.2–6.5.

Regularly test your soil with the tools mentioned above and adjust accordingly. If your pH is too low, try adding dolomite to bring it up. If it’s too high, pine needles can naturally work to bring it down a notch.

Three Basic Cannabis Cultivation Methods

The Process Behind Forced Flowering And Why You Should Do It

6 Steps To Getting Maximum Yields From Autoflowering Strains

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Autoflowering cannabis strains grow fast and are easy to cultivate, but they require a specific type of soil to really thrive. Find out how to make it here.