The Best Soil For Growing Autoflowering Cannabis

Autoflowering cannabis strains are loved for their hardiness, quick flowering times, and how easy they are to cultivate. And unlike feminized strains, they aren’t photo-dependent. This makes them popular among experienced growers and ideal strains for newbies. But if they’re to provide the yields you crave, it’s vital you know about the best soil for autoflowers.

Their short growing cycles mean there’s little room for error. Planting your seeds in the right substrate — and maintaining the right conditions throughout the growing process — is imperative if you want your plants to thrive.

What Type of Soil Should You Use?

When it comes to autoflowers, aeration is the name of the game. Be sure to use light and airy soil. This increases root oxygenation and allows roots to grow deeper. The more oxygen a plant receives, the faster its metabolic process will be, and the more quickly it will grow. As the vegetation phase of an autoflowering strain tends to last just one month, it’s important to make the most of it. Maximize aeration to maximize your yields.

It’s also worth noting that autos require fewer nutrients than their feminized counterparts. Cannabis soil that is too nutrient-heavy will stunt their development. As will dense soil that holds excess moisture. We’ll touch on this more below.

Maintaining the Correct pH

But first, the importance of keeping your soil at the correct pH. The pH scale goes from zero to 14: pH levels below seven are acidic; seven is neutral; and levels above seven are alkaline. When growing cannabis, your soil’s pH impacts the plant’s ability to absorb nutrients. As such, it has a huge bearing on growth, and symptoms of poor soil pH are often mistaken for nutrient problems.

The best soil for cannabis growing should have a pH in the range of 6-6.5. Be sure to test it regularly and adjust it if necessary. There’s a wide variety of testing equipment on the market, from digital probes to paper strips, and a number of ways you can treat it. Dolomite can increase the pH level of your soil, while pine needles are an effective natural method of lowering it. If you’re struggling to keep it under control, also check the pH of the water you’re giving to your plants.

Applying Extra Nutrients

Overfeeding autos is a common beginner’s mistake. Thanks to their relatively small size and short growth times, they don’t require the same amount of nutrients as feminized strains. Apply supplements sparingly.

During the seedling phase, autos shouldn’t require any additional nutrients if the soil already contains them. You may begin adding nutrients after a couple of weeks, but only very lightly. The short vegetation phase means it isn’t necessary to increase nitrogen levels in the way it is with photoperiod strains. If you overdo it, you can burn the plant, reducing the size and quality of your yield.

It can take up to two weeks to recover from nutrient burn. This is a significant portion of the growth cycle of an autoflowering strain — and valuable time lost. When growing autoflowering cannabis, it’s better to take a “less is more” approach to nutrients. Embrace the low-maintenance cultivation process that makes autos so popular.

Making Your Own Soil Mix

Soil mix

Given the unique requirements of autoflowering strains, many growers recommend making your own soil mix. Thankfully, this is quite easy. The ideal mix for growing autos can be made by combining peat moss, compost, perlite or coco coir, and vermiculite in the following ratio:

3 parts peat moss

3 parts compost

2 parts perlite or coco coir

1 part vermiculite

This simple recipe provides the right balance of nutrients for your plant. And materials like perlite, coco coir, and vermiculite enhance the aeration of the substrate, giving you an effective cannabis soil that you can make at home.

Other Mediums for Growing Autoflowering Cannabis

But soil isn’t the only suitable medium for growing autoflowering cannabis. Autoflowering seeds can also be cultivated in materials such as coco coir and worm castings, and using hydroponic systems.

Coco Coir

Coco Coir is fibrous peat made from coconut husks. When added to a soil mix, it makes the soil more lightweight, increases air pockets, and wicks away unwanted moisture. It can also be used as a growing medium by itself. In this case, it has the added advantage of coming with a pre-adjusted pH. All of these factors make coco coir synonymous with high yields and an easy medium to use.

One drawback is that it doesn’t contain any nutrients, so you’ll need to apply them from the first week of growth. But this also enables you to customize them precisely to match your needs.


Hydroponic grow room

A hydroponic setup grows plants by soaking their roots in water. Or, more specifically, in water that’s full of nutrients and oxygen. Applying these essential inputs directly to the roots causes plants to grow bigger and faster.

The initial setup requires some equipment: you’ll need a water pump, an air stone (for certain systems) a timer, and at least two reservoirs. You’ll also need to measure the pH and PPM levels every day. But you’ll be rewarded in the long-run. Once established, hydroponic systems are low maintenance and highly productive.

Worm Castings

Worm castings are a fertilizer manufactured from worm excrement. They’re not a growing medium in their own right, but they can be a useful addition to a soil-based substrate. We’d recommend a mix of 50% basic soil (free from additional nutrients), 25% perlite or coco coir, and 25% worm castings. Place the worm castings at the bottom of the pot so that roots can only reach them one they have grown sufficiently. This will provide your plants with a moderate nutrient boost without overfertilizing them.

A Few Final Pointers

Now before you get started, here are a few final tips to help you on your way:

Don’t Let Your Soil Get Too Moist

Roots only absorb enough oxygen when they’re not wet, and over-watered soil inhibits growth. Only water your plants every second day or when the soil has completely dried out during the vegetation phase. This way, their roots will expand in search of water.

Don’t Re-Pot

Don’t stress your autos out if you want to maximize their yields. Plant them straight in their final location to avoid the stress of re-potting.

Use Pots That Maximize Aeration

Aeration is key to a healthy, high-yielding plant. And after your growing medium, the most important factor here is your pot. We recommend using a smart pot or an air pot in order to get the best results.

To Sum Up

Ultimately, there are just a few fundamentals when it comes to planting autoflowering cannabis. Remember that aeration is king. The best soil for autoflowers will be light and allow plenty of oxygen to the roots. Don’t overdo the nutrients! Autos take less feeding and will suffer if you do too much. Know that it’s possible to make your own effective soil mix. And get the right pot. A container that maximizes airflow and provides good drainage is essential. And finally: soil improves over time. The more growth cycles you attempt, the better it will get.


6 Replies to “The Best Soil For Growing Autoflowering Cannabis”

  1. I was wanting to know what brands of soil to use.. i dont wanna make mine.. and where can i find step by step instrutions on how to grow autoflowers

  2. I have a few bags of burpee, natural and organic raised garden and container mix .11-.11-.11. Will this be ok for autos?

  3. I’m looking to buy soil for autoflowers indoor grow I work a lot of overtime so I need soil that I don’t need to add anything to feed it.I bought a ppm ec meter and ph meter the ph meter I have to keep calibrating it I’m out of the solutions for calibrating so I need to find a ph meter that works and I don’t have to calibrate it every day.

  4. Hi All….need a bit more information on the DIY soil mix. What is a “part” is it a weight or a volume? Ingredients for the mix appear to be volume but want to check.

    Thanks for the info!

    1. A “part” is any unit of measure. It could be a tablespoon, an ounce, or a gallon. One part vinegar to two parts water could be 1tbsp vinegar and 2tbsp water, for example.

  5. Soil improves over time. Do you mean use the same soil over and over or I will get better at building my own soil with every new batch

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