Important Cannabis Soil Considerations

  • Texture
  • Drainage Ability
  • Water Retention

the most important aspect of any soil is actually its texture, ability to drain, and overall water “holding” ability.

for a cannabis plant to grow and thrive, it needs a good mix of both water and oxygen at the roots at all times! Too much water and the plant roots can’t get enough oxygen (lack of oxygen at the roots is why plants get droopy from overwatering

“Good” Cannabis Soil Ingredients
Composted forest humus
Sandy loam
Sphagnum peat moss
Coco coir (sometimes labeled coco fiber)
Perlite
Earthworm castings
Bat guano
Fish meal
Crab meal
Bone meal
Blood meal
Azomite
Pumice
Kelp
Dolomite lime
Greensand
Mycorrhizae
Leonardite

Alter Texture, Drainage & Water Retention of Soil

Perlite

  • Perlite is one of the most common soil amendments. It is highly recommended for any soil mix that doesn’t have some already.
  • Very light, airy white “rocks” that feel almost like popcorn and add oxygen while increasing overall drainage ability.
  • Add perlite to the mix (10-40% of the total volume). Use less perlite if you want better water retention and don’t plan on using a lot of extra nutrients. This is because a lot of extra perlite can cause the nutrients leach out faster from the soil. Add higher levels of perlite if you want to use a lot of added nutrients or supplements without burning your plants (since perlite helps prevent nutrient buildup).

Vermiculite 

  • Vermiculite “lightens up” heavy soil and improves water retention.
  • Some growers use perlite and vermiculite interchangeably, though they’re not exactly the same. Vermiculite holds water much better than perlite, but is not as effective at adding aeration and drainage.
  • Some growers use a little bit of both. If you go high with vermiculite, you don’t want to go as high with perlite and vice versa. Together, perlite and vermiculite should never make up more than 50% of your soil!

Coco Coir

  • Coco coir is made from coconut husks. It can be purchased as loose coco coir, in an amended potting mix, or as coco bricks which needs to be rehydrated before use (learn how to re-hydrate coco bricks). Sometimes you’ll find a “soil” mix that is pretty much all coco plus amendments, and these can be a great choice for cannabis. Coco has some unique properties that make it a good supplement for cannabis soil mixtures.
  • Coco improves water retention, but doesn’t make soil heavy.
  • Roots tend to develop faster and plants are less likely to suffer from overwatering in coco coir.
  • Some growers grow in pure coco, but if you’re adding it to a soil mix as an amendment, you might add 10-30% coco coir.

Worm Castings

  • Worm castings is a nice way of saying worm poop, and cannabis plants love it!
  • Improves texture, drainage and moisture retention
  • Add a natural source of nutrients that breaks down slowly
  • Usually contains high levels of beneficial micro-organisms due to going through a worm’s digestive system 🙂
  • Add up to 30% worm castings in your soil (although it contains nutrients, it’s gentle enough that it’s unlikely to burn your plants even if you add too much)