Super soil is a heavily amended, composted organic mix that feeds a cannabis plant from early veg through most of flower with plain water alone. The recipe is not complicated: a quality potting soil base, roughly a quarter of the volume in worm castings and compost, 10 to 15 percent aeration, then dry amendments measured per cubic foot. Mix it, keep it damp, and let it cook for four to eight weeks before anything goes in the pot.
The base mix ratio
Think in parts by volume, not by weight. A batch of about 2 cubic feet (15 gallons) is a good size for a few plants and easy to turn by hand.
Using Super Soil in Pots for Cannabis
- 60 to 70 percent base potting soil. Look for one that already contains coco or peat and mycorrhizae.
- 20 to 25 percent worm castings and finished compost, split however you like. Castings bring biology; compost brings bulk and more biology. If your compost source is uncertain, lean on castings.
- 10 to 15 percent aeration: perlite, pumice, or rice hulls. Pumice lasts longer and does not float to the surface the way perlite can.
That base is your growing medium. The amendments below turn it into super soil.
Find the Best Cheap Super Soil Mix for Growing Weed
Amendment rates per cubic foot
These are moderate rates. Published recipes disagree by a wide margin, and going heavy is the most common way people burn plants, so start here and adjust next run.
Super Soil Cooking Time for Cannabis Guide
- Blood meal: 1/2 cup (fast nitrogen)
- Bone meal: 1 cup (phosphorus and calcium)
- High-phosphorus bat guano: 1/4 to 1/2 cup
- Kelp meal: 1/2 cup
- Alfalfa meal: 1/2 cup
- Rock phosphate: 1/4 cup
- Greensand: 1/2 cup (slow potassium)
- Azomite or glacial rock dust: 1/2 cup (trace minerals)
- Dolomite lime or oyster shell flour: 1/4 to 1/2 cup (pH buffer and calcium)
- Epsom salt: 1 tablespoon (magnesium and sulfur)
- Humic acid powder: 1 tablespoon
- Mycorrhizae: follow the label rate
A handful of bone meal or guano tossed on top of the base mix is not the same as measuring. Scoop level, and turn the whole pile twice so nothing clumps into one corner of a pot.
Mixing and cooking
- Spread a tarp, dump the base mix, castings, compost, and aeration, and turn it with a shovel until the color is even.
- Sprinkle the dry amendments over the pile in layers as you turn. Big dust clouds mean you are pouring too fast.
- Add water until the mix holds together when squeezed but no drops come out. Dry super soil will not cook.
- Cover the pile or fill a bin, and keep it out of direct sun. Aim for 60 to 80 degrees Fahrenheit.
- Turn it every week or two. It will warm up and smell earthy, then settle down.
- Wait at least four weeks. Eight is better. Three months is better still if you plan ahead.
Using it in the pot
Super soil is hot, so a seedling or fresh clone should never start in it. Fill the bottom 60 to 70 percent of the pot with super soil and the top 30 to 40 percent with plain base mix. Plant into the plain zone. Roots grow down into the rich layer as the plant gets bigger and can handle the strength.
For a long veg, a 7 to 10 gallon pot gives roots enough room to reach the food. Small pots run out before flower even starts.
Watering through the cycle
Plain water, pH 6.2 to 6.8, and no bottle feeding unless the plant asks for it. Keep the mix evenly moist, never soaked and never bone dry, because the microbes doing the work need water. A top dress of worm castings plus a bloom amendment around week four of flower covers most strains. If leaves yellow from the bottom up in mid-flower, that is the mix running low on nitrogen, not a mystery.
Mistakes that cost a run
- Planting too soon. Unfinished super soil burns seedlings and stalls clones for weeks.
- Doubling the amendments "to be safe." More is not better; it is a salt problem.
- Skipping aeration. A dense mix suffocates roots no matter how good the food is.
- Using a cheap base soil loaded with wetting agents and slow-release fertilizer. You lose control of the feed curve.
- Letting the pot dry out completely between waterings. That kills the biology you paid for.
Before you mix
Home cultivation rules vary by state and by county, and some places cap plant counts or require registration. Check your local rules first. Nothing here replaces a soil test if you are mixing large volumes and want to dial in the numbers.