How to make super soil for autoflowers

When gardening, it’s best to let nature do her thing by providing the right conditions. With that in mind, let’s discuss how to make super soil for autoflowers. Making the effort now to create a premixed soil for autoflowers will save a lot of work later and pay off big at harvest time. 

The best organic super soil for autoflowers will supply the right nutrients at proper ratios for great growth and flower production without complication and excessive effort. This will help make your harvest a more rewarding experience. This super soil mix for autoflowers article is a follow-up to “What is the best type of soil for autoflower cannabis?” where I discuss the basics of autoflower soil requirements.

What is supersoil?

Super soil is a soil mix with all the necessary nutrients and aeration ingredients, mixed thoroughly and composted for at least 30 days before use. This process allows the soil biology to multiply and break down the nutrients for the plant to use safely without causing nutrient burn. A biologically active super soil mix like this can form the basis of a living soil recipe for autoflowers (note: these two soil types are not the same) and is often used in conjunction with regenerative farming techniques.

A small auto cannabis plant sprouting out of the super soil

A super soil recipe for autoflowers can be made by adding dry fertilizer amendments and soil inputs into a base soil mix supplied by your local garden center, grow store, or farm supplier. Some premixed soils available from grow shops are actually bagged super soils. Some companies manufacture super soil mixes where I live (Willamette Valley, Oregon).

If you want to see how the super soil recipe works for autoflowers, get your own autoflower seeds here and follow the instructions to create super soil below!

bergman holding autoflower plant

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Cultivators who grow in super soil add mycorrhizae (a beneficial fungus for plant roots) to aid and increase the uptake of nutrients by cannabis plants, which will increase a plant’s growth rate and biomass. This autoflower super soil, with proper nutrients and aeration, is essential for maximizing the growth and yield of your autoflower plants.

How to make your own super soil for autoflowering cannabis

I have been using a soil mix recipe base I discovered over a decade ago as a starting point for a mix that I have since modified and added other ingredients to. This recipe provides enough super soil to last a home grower (2-4 plants per cycle) for half a year. You’re free to make smaller amounts if you can divide them properly. 

Learn how to maximize your autoflower grow with our famous Grow Bible by Robert Bergman!

I have used various combinations of soil, coco fiber, and peat moss over time, but I’ve since reverted to using just bagged soil (Black Gold works very well) as my base mix. Please note: all nutrient measurements in (ml) indicate the amount of nutrient to use per 1 CF of mix. This mix yields 12 CF of soil mix. For example, 120 ml of bat guano per 1 CF x 12 CF= 1,440 ml total.

  • 4-6 large bags of a high-quality organic potting soil with mycorrhizae (4 bags if they’re 1.5 cubic feet, 6 bags if they’re 1 cubic feet) Hereafter, CF=cubic feet
  • 2 bags of 100% worm castings (1 CF each) 
  • 1 bag of quality compost (1-1.5 CF)
  • 2 CF of rinsed perlite, rice hulls, pumice, or lava rock (aeration):
  • ½ CF bag biochar (nutrient holding)

The following amendments are measured in ml per 1 CF of mix: 

  • ½ cup (120ml) bloom bat guano (high P)
  • ½ cup (120ml) bat guano (high N)
  • 1 cup (240ml) steamed bone meal or fishbone meal (nitrogen + phosphorous)
  • ½ cup (120ml) feather meal (nitrogen + enzymes)
  • ¼ cup (60ml) rock phosphate (phosphorous)
  • ⅛ cup (30m)l Epsom salts (magnesium + sulfur)
  • ½  cup (120ml) Gypsum (calcium + sulfur)
  • ½ cup (120ml) azomite (trace minerals)
  • ⅛ cup 30 ml granular humic acid (nutrient uptake)   
  • ½ cup (120ml) Neem cake (insect control)
  • 1 cup (240 ml) Oyster shell flour (calcium)
  • ½ cup (120ml) Kelp meal (potassium + trace minerals)
  • (5 ml per liter of pot size) granular mycorrhizae (at planting)

Time needed: 14 days

  1. Purchase your ingredients

    Purchase all the ingredients you will need for your mix and gather them together. Make sure you’re wearing a respirator (preferably) or particulate mask when mixing soil and amendments. Many fine particles can easily get into your eyes or lungs. Wear long sleeve clothing, gloves, and a hat to keep particles off your skin and hair. Use a scrubbing fan/filter combo for larger mixes to account for the dust that will be created. This is a bigger issue indoors.
    Use a garden spray bottle (4-liter size) of water for dust prevention and mix hydration).Creating Super Soil Compost Step 1

  2. Setting up your mix

    Use a clean space free of debris and protected from the wind. Set up a tarp, kid pool, or other container (I recommend 8’ x 10’ size or larger) on the floor or ground. A clean concrete floor is ok if it’s all you have. 
    Empty half of your bagged soil and spread it out, breaking up any clumps or bricks. Slowly empty the perlite on top of the soil mix (it’s very dusty). Add the worm castings and compost on top of the perlite, then add the rest of the bagged soil over the top. Mix the base inputs together thoroughly for at least 3 minutes. I mix with my hands first and then roll the soil over inside the tarp. Creating Super Soil Compost Step 2

  3. Mixing your super soil

    Spread the soil back over the tarp and even it out the best you can. Take each fertilizer material and spread it evenly over the pile, one at a time, trying not to create too much dust (nearly impossible). 
    Mix the soil thoroughly using the same method for at least five minutes. You should hand mix every sq ft of the tarp thoroughly and then roll it several times. I prefer to do it this way because it gives me a better visual of how mixed the soil is. I know I am done when I can no longer see the fertilizer layer on top anywhere in the mix. Creating Super Soil Compost Step 3

  4. Moisten the mix

    Next, it’s time to moisten, not flood, the mix with water to facilitate the composting process better. Spray the mix evenly and then pour 2–3 liters evenly over the mix, give a quick hand mix, then roll once more before leaving the pile covered for composting. 
    You will want to mix and roll once every 48 hours and maintain the moisture level, allowing the soil mix to compost evenly. Let your mix sit in the tarp this way for two weeks.Creating Super Soil Compost Step 4

  5. Storing your soil

    After two weeks, most of the composting will have occurred, and you can transfer your mix into a container for storage or leave it composting in a tarp for more immediate use. Check your soil for any spots that are still warm to the touch, and remix. 
    NEVER use soil that is still hot from composting; it will burn the plant roots.Creating Super Soil Compost step 5

If you want quality autoflowering seeds to use your super soil on, try ILGM’s autoflower super mix for optimal results.

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Why is quality soil important for autoflowers? 

It’s important to start with quality soil when cultivating cannabis. You can’t grow it in crap and expect great growth and flower production. A super soil for autoflowers will do most of the hard work, saving you time and effort, especially as the plant is flowering and finishing. 

This autoflower super soil recipe is designed to only require the use of water after planting. We are eliminating the need to use liquid fertilizers or do extra work. That way, you can focus on perfecting your watering technique and making plant observations. 

A great cultivator makes the effort to observe. You can see plant progression on a daily basis at times, and any early problems are much easier to deal with. If you can, sit and practice moments of stillness and observation in your garden. It’s a great way to let nature pass her secrets to you. You can even add a few worms to each container and let them do some of the work for you!

How much super soil does an autoflower need?

After your autoflower soil mix has composted and is ready to use, it will still be quite potent and could cause damage if used with intense direct light or in high-temperature settings. There is a lot of stored energy in those nutrients (N-P-K are used in explosives manufacturing)

Learn the best tips and tricks to maximize your autoflower yield in our dedicated guide!

If you germinate seeds directly in super soil, you will need to dilute the mix considerably. I suggest thoroughly mixing 1 part super soil with 3 parts bagged soil to avoid nutrient burn. 

Two small auto cannabis plant sprouting out of the super soil in two different containers

Exercise caution when using a 100% super soil mix directly for autoflower cannabis. There is virtually no time to recover from nutrient burn damage. Keep in mind some cultivars will be less tolerant than others. You can easily dilute the mix you made with regular bagged soil whenever necessary.

If you’re only using one container for your entire autoflower cycle, start by layering the bottom third of the container with super soil. The middle third will be 50/50 diluted super soil, and the top third, bagged soil with 50/50 diluted super soil around the outer edge of the container.

Make a small transplanting hole for the seed in the middle of your container. I push my index finger down to the middle knuckle and then drop the seed in, moving the soil over it to close it up. Don’t place the seeds too far down where they’ll be susceptible to excess moisture or low oxygen. You want them to be able to break through the soil and get to the light relatively quickly. 

When it’s time to harvest your autoflowers, read our comprehensive guide on harvesting to learn everything you need to know.


Give your super soil mix at least 30 days (or longer) to compost before using it for your autoflower cannabis. This will help prevent accidental damage due to nutrient burn and ensure a healthy plant response. 

Mixing and making the best super soil for autoflowers is an effective way to get customized, complete nutrition for your plants as inexpensively as possible. It also gives you a medium that requires only plain water to maintain. Your mix can be stored indefinitely until needed. 

Getting your hands in the soil and on the plants is important. Plants respond to stimuli like sound and vibration. Making your own soil is a highly satisfaction, educational, and bonding experience. I feel like it brings me closer to the plants and my humanity. It’s a time-consuming yet satisfying experience.

The trade-off is time and effort. Making soil is a dirty, dusty experience. Always use gloves, a respirator or fine-particle mask, and long-sleeve clothing. Some people would prefer to buy their soil ready-made. That’s up to you, as you now have a clearer picture of the time, effort, and budget you want to spend on your plant nutrient needs.  

I have spent 20+ years growing cannabis. In that time, I have witnessed how more biologically active soils produce a premium quality flower with high potency and superior terpene-flavonoid profiles. I have experimented with every type of medium and method of growing in a quest to find the perfect combination of plant and medium. That’s what happens when you’re a connoisseur; you want to provide the perfect recipe for each individual cultivar. 

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FAQs about using super soil with your autoflowers

What is the best way to store super soil?

I prefer to store my unused super soil in clean, rolling, upright trash bins with covers. This gives me a vertical storage option I can move around. If you cultivate indoors, transportable super soil makes life easier when you need room to transplant, harvest, or perform extra maintenance.

Can I use my homemade compost in my super soil Mix?

Unless you’re a composting expert, do not use compost from the pile in your yard, particularly if you’re growing indoors, as you may bring in potential pests from the outside. If you must, mix it into your super soil recipe and let it compost further.

Do I need to pH my water for super soil?

Many cultivators say they don’t need to alter the pH of their water when growing with super soil. This makes sense when you aren’t adding fertilizers and additives to your water. It is standard procedure, however, to check the pH of the water you are using to get a readout on your water source. If your water is naturally high in minerals, you may need to filter it (which you should do anyway to remove chlorine and chloramines) or use reverse-osmosis treatment. 

Can you top dress with super soil?

You can top dress with super soil if the plant is mature enough to avoid nutrient burn when doing so. I prefer using worm castings and supersoil mixed together for top dressing. If it’s within two weeks of harvest, worm castings are enough to top dress.

Should I add worms to my super soil?

Personally, I will add worms to my containers when transplanting, but I prefer to leave them in my composting worm bin until I’m ready to use them. I don’t add them to my composting or stored super soil mixes.

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Jason Bird

Cannabis indoor cultivation expert

Jason Bird has been cultivating organically-grown cannabis in Portland, Oregon, since 1996 and graduated with an AAS degree i ... See profile

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