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Which Soil Is Best For Autoflowers?

If you’re growing autoflowering cannabis, it’s a safe bet that you’re looking to take the less-stress approach to producing weed. After all, autos are known for their sturdier genetics, less reliance on a rigorous light schedule and lower need for nutrients. But what do you plant them in? Which soil is best for Autoflowers? Here, we’ll look at the ins and outs of autoflower soil and cover things new cannabis growers need to know.

What we know about Autoflowering Cannabis

As noted, autos are a good solution for growers seeking a lower-maintenance project. By taking a popular photoperiod strain and crossbreeding with Ruderalis genes, you get a solid plant that demands a little less of your attention than a typical photoperiod strain. That’s not to say you can plant them and leave them, of course – autoflowering cannabis strains have needs, too. They’re just a little less needy.

Autos typically Finish Faster

On average, autoflowering cannabis gets to the flowering stage a little bit quicker and finishes quicker, too. You’ll seldom see an auto go beyond about 8 or 9 weeks into flowering, whereas a photoperiod strain may take 10 weeks, 12 weeks, or even longer to get to the harvesting stage.

Autos Need Fewer Nutrients

Thanks to their Ruderalis genetics, autoflowering cannabis strains tend to have a bit more get up and go of their own accord. They’ll still reward you for nutrients (potassium, nitrogen, and phosphorous), but you can dole these out in lesser doses than with a photo strain. Autos are hardier and more resilient by nature, so they’ll get the job done without needing the same help.

Autos Don’t Rely on Strict Light Schedules

Again, being blessed by those wonderful Ruderalis genetics – specifically, genetics from roadside plants that adapted to harsher climate and lighting conditions in the extreme regions of the Northern Hemisphere – means autoflowering cannabis will jump to flowering without the same need for light manipulation as their photoperiod equivalents. That’s not to say you can grow them in a dark cupboard and expect killer cannabis, though. They still have their needs in terms of light, but they’re a lot less demanding.

The best Soil for Autoflowering Cannabis

You have a little more leeway when it comes to autoflowering cannabis cultivation. But although there’s a broader, more forgiving margin for error, there are still considerations when it comes to getting the best from your autos. One of those is the type of soil you choose to plant your autos in. The plants aren’t overly fussy about the soil they find around their feet. But if you make an informed choice, there’s a good chance your plants will thank you with better growth and a harvest of better quality cannabis.

Soil Specifics for Autoflowering Cannabis Plants

Autoflowering strains benefit from well-aerated soil. In other words, light, airy soil with the right amount of nutrients and a little acidity. This is what some experienced growers call super soil. Your autos need this to allow them to spread and grow because heavier potting soils will mean the roots are more likely to struggle to stretch out underneath. You can buy an excellent light cannabis soil for autos, or you can make your soil with a relatively simple recipe such as this one:

  • 3 parts compost
  • 3 parts peat moss
  • 2 parts perlite – to help drainage while still allowing necessary water retention*
  • 1 part vermiculite – for its near-neutral Ph

*Don’t overlook the importance of good drainage when it comes to creating an ideal environment for our autoflowering plants; this is as vital as good aeration and the growing medium itself.

You could simplify this further by taking 80% regular soil, adding 10% coco coir and 10% perlite, and then creating the potting mix by hand. This has the added advantage of being cheap, quick, and easy. Then, ensure you use a large pot (preferably fabric or an air-pot), and you’ve crafted an ideal environment for your auto’s roots.

The main thing is that your soil is light and airy to give the root zone adequate room to breathe and stretch. Cannabis plants thrive best in a well-oxygenated medium, so ensure your substrate choice is precisely that.

Benefits of Organic Soils and Amendments for autos

Using organic soil is a good bet, as overly nutrient-dense soils can easily cause nutrient burn in your autos. Organic soils contain less nutrients, which is better for the lower nutrient dependency of autoflowering cannabis.

Organic soils contain beneficial microbes and mycorrhizae that your autoflower needs to thrive, but organic amendments and additives are equally helpful to your autos. You can add numerous types of organic amendments to your soil, which help improve moisture retention and overall soil health. Bat Guano is suitable for nitrogen, but you can also use Manure, Worm Casting, Bone Meal and Blood Meal. Wood ash and Kelp meal help with potassium levels are all easily obtainable; introducing these to your soil before planting will help create the ideal environment for your plants. These soil amendments will not only assist the root zone either. They can even help you maximise cannabinoids and terpene profiles.

Take care to follow instructions, though. Something like Bat Guano needs only a small amount; otherwise, you can do more harm than good.

Believe it or not, you also want a degree of fungal presence in your soil. This will help distribute nutrients through the soil to the roots. Adding mycorrhizal amendments to your soil can help immensely with this.

Can you Grow Autoflowers in Regular Soil?

Absolutely, and those Ruderalis genetics make pretty much anything possible. However, using a lighter soil mix will maximise your yield and offer benefits regular potting soil may not. It’s up to you which route you take, and there’s no harm in using regular soil if that’s all you have at your disposal. Likewise, if you’re cautious about mixing your own product. But since lighter, more suitable high-quality soils are widely available, it makes sense to give your autos something closer to what they need to achieve the best results.

Cultivation information, and media is given for those of our clients who live in countries where cannabis cultivation is decriminalised or legal, or to those that operate within a licensed model. We encourage all readers to be aware of their local laws and to ensure they do not break them.

Duncan Mathers