The Best Soil for Autoflowers

Autoflowers have a shorter lifespan than their photoperiod counterparts, flowering in approximately eight to ten weeks after they are planted. Because of their shorter life cycle, they have to use each day to the fullest, growing optimally to ensure the best yield.

From access to sun and water to nutrients and optimal light and temperatures, your autoflowers will thrive if you give them the right conditions.

However, it all starts with the best soil.

The naturally occurring nutrients and microorganisms that organic soil contains create the optimal environment for plants to grow happy and healthy.

In this article, we’ll look at the best soil composition for your autoflowers and give you everything you need to grow these hardy plants.

Key Takeaways

1. Consider purchasing commercially-available soil or making your own soil.
2. Organic soils are generally better for autoflowers because of their natural nutrient profiles and ability to support healthy microbial life.
3. Learn how to manage soil pH levels at the optimal range of 6.0 to 6.5 to ensure optimal nutrient uptake.
4. Invest in the right soil from the start to give yourself a better chance of success.

Why Soil Choice is Important for Autoflowers

Autoflowers grow extremely fast, so if you make the wrong soil choice, there’s no room for correction. The soil is responsible for water retention, the availability of nutrients, and ensuring proper root health.

You want soil that is nutrient-rich, packed with microorganisms, disease-free, and airy. But first, let’s look at the lifecycle of an autoflowering cannabis plant.

Autoflowering Cannabis Growth Cycle Overview

Autoflowers are a feminised weed variety that grows on an incredibly fast timeline. They evolve from germination then vegetation, to flowering and harvest in about 10 to 12 weeks, depending on the strain.

Germination and seedling sprouting take up the first 2 weeks of your autofower’s lifespan. The seedlings grow roots in your grow medium (whether that be soil or hydroponics), and a couple of leaves show up as well.

The vegetative stage typically takes place over weeks 3 and 4. Most autos grow incredibly bigger and stronger during this period of their lifespan.

By week 5 to week 7, your autoflower should have entered its flowering stage. If everything goes well, you should already see a couple of buds.

The buds will swell up and mature, and by weeks 8 through 10, you should be harvesting your buds. However, some strains might take longer and some strains flower even quicker.

Key Characteristics of the Best Type of Soil for Growing Autoflowers

    Airy and Fluffy Soil

Avoid buying heavy, dense soils as the roots of your autoflowers need good aeration to thrive.

Commercially-available organic soil would be the most fuss-free way to do this. Not only will the have the optimal mixture, but they will also have beneficial microorganisms that release helpful bacteria to help fight infections and diseases.

But if you’re committed to a DIY soil mix at home, you can add substrates to create an airy and fluffy soil mix. Common substrates include perlite, vermiculite, coco coir, and peat moss.

We’ll look more at these substrates in a later section.

• Water and nutrients

You want soil that holds just enough water for the roots, but not too much so they get waterlogged and suffocate. Clay holds way too much water for autflowers, so avoid this medium. A good soil substrate that holds just enough water and nutrients is biochar.

Certain growers swear by nutrient-rich soils from the start, but some growers prefer to use a light mix of soil, leaving room for adding nutrients as needed over the plant’s lifecycle.

The light mix soil is the safest approach because an overload of nutrients in the early stages of the auto’s lifecycle could stunt growth and even kill the plant.

Seedlings require fewer nutrients than those in the vegetative stage, so if you start with a light mix, you can easily control the amount of nutrients you feed.

Start with a light mix and raise the nutrient level as your plant grows, but watch closely for signs of nutrient burn like burnt leaf tips of yellowing leaves.

Organic vs. inorganic soil

Organic soils are great for your autoflowers, and they benefit the environment too. In organic soils, you’ll find naturally occurring microorganisms produce beneficial bacteria in addition to essential natural nutrients.

Inorganic soils are more sterile and require artificial fertilisers to give plants the nutrients they need.

In general, we’ve found that autoflowers grown in organic soil tend to have a more robust flavour and aroma, likely due to the rich, natural nutrients they’re absorbing.

Common Organic Soil Amendments

Organic soils are amazing, but you can go the extra mile to amend them with staples to give the quality an additional boost.

Common staples that will improve your soil’s structure and nutrient content include worm castings, bat guano, compost, and bone meal.

Bone meal is particularly high in phosphorus, making it excellent for root growth.

Compost and bat guano pack more valuable nutrients into your soil, while worm castings will provide beneficial bacteria.

Recommended soils and potting for Growing Autoflowering Cannabis

Now let’s look at mixing the soil, its substrates, and its staples into your pot so you can best plant your feminised autoflower seeds.

Best Potting Mixes for Marijuana (Recipe)

You have two options, the first one being starting with 80% organic soil and then adding 10% coco coir, 5% perlite or vermiculite, and 5% compost.

In the second option, start with 70% organic soil, 15% coco, 10% perlite or vermiculite, and 5% compost.

These are your base mixes and to these, you can add some more amendments (staples). Consider worm castings as they’re easier to find and loaded with microbes the autoflowers will love.

Both mixes give soil sufficient drainage, enough aeration, and a precise supply of nutrients that will grow thick, potent autoflower buds.

Perlite

Perlite is important because it will keep the soil fluffy which is excellent for root growth. Perlite works with vermiculite (optional) to help with aeration.

Don’t mix in too much perlite because you don’t want to over-aerate the soil, causing it to dry out quickly.

Coco coir

Coco coir (coconut fiber) also makes your soil mix lightweight and airy, helping create air pockets to help the roots obtain oxygen.

When the soil is well aerated, you get more extensive root systems that translate to larger, flourishing plants.

 Biochar

Another option to enhance the quality of your soil is biochar.

Biochar is pure carbon which can help break down the organic matter in the soil, resulting in more nutrients available for your plants.

Use it with care and do not use too much of it. Because it can absorb a remarkable amount of water and nutrients, if you overuse it, it can starve your plants.

Vermiculite

Vermiculite is another naturally occurring mineral that can also be added to your soil, helping with aeration.

It stores water and doesn’t change the pH, but just like with biochar, don’t add too much because that can hold a lot of water and nutrients, which could harm your autoflowers.

Specific Soil Brands and Products for Autoflowers

If you want to skip all this work and get commercially available soil, Fox Farm’s Ocean Forest soil is an excellent choice.

It’s organic and has a well-balanced nutrient profile so you can go straight to planting your auto seeds once they hit your doorstep.

Black Gold also has a natural and organic potting mix that’s lightweight and loaded with beneficial microorganisms.

What is the Best Super Soil Recipe for Autoflowers?

Once you put together your own super soil mix, you’ll never need to add any nutrients again until your buds are ready for harvest!

Here’s how you make your own super soil:

You get a base of quality organic soil, and to this base, add all the amendments we’ve described earlier: compost, warm castings, bat guano, blood meal, bone meal, and kelp meal.

Leave this super mixture alone for about 3 weeks and then you can plant your autos.

Essential Nutrients Autoflowers Need

We’ve talked a lot about nutrients, but what specifically are we referring to?

The nutrients you’re aiming to give your autoflowers through the soil are nitrogen (N), phosphorus (P), and potassium (K). These are called macronutrients and if they’re lacking, your plants might run into all sorts of disease and growth problems.

NPK is the most important combo you should care about if you’re trying to provide nutrients to your autoflowers artificially. The 4-2-3 (N-P-K) ratio is what’s most appropriate for plants in the vegetative stage. And as the plants flower, the ratio shifts to 2-8-4 because of a higher need for phosphorus.

Good soil vs. bad soil for autoflowers

How can you tell good soil from bad?

• The smell

The smell is the first great indicator of good soil because bad soil kind of stinks since it has bad bacteria present.

• Density:

The next thing is how dense your soil is. Don’t buy super-heavy and dense soils.

• Coker and Perlite

Good-quality soil has coker and perlite already mixed into it unless you buy additional worm castings.

The package should also tell you the nutritional value, show how much the NPK is, and tell you the ingredients.

Best pH for Autoflowering Soil

As a side note, you also want to keep an eye on the pH, maintaining it somewhere around 6 to 6.5, and no more than seven or lower than six.

Use a simple pH metre to test your soil’s pH as often as you can, especially after watering or adding some artificial nutrients.

If you notice a higher soil is too acidic (lower pH), add lime to raise the pH. If the soil is too alkaline (higher pH), you can add some sulphur or aluminium sulphate to bring down the pH.

Shop The Best Cannabis Seeds For Australia here

FAQs

Still have a few more questions?

Can I Use Regular Potting Soil for Autoflowers?

You can use regular potting soil for autoflowers but it might not give great buds in the end. Most commercial potting soils are heavy and might not even have the right nutrient balance for autoflowers.

How Often Should I Water Autoflowers?

This really depends on the environmental conditions of your growing environment. To make it easy, just touch the top inch of your soil; if it’s dry, you should water it. Some growers also prefer to stick to a 2-day schedule, particularly in the early stages.

Conclusion

Now that you know how to find the best soil for your autoflowers, you’re going to need some choice seeds. That’s where we come in! Shop for top-quality autoflowering, feminised seeds that the top growers in Australia use.