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best cannabis seed starting soil

When buying seed starting mix, you’ll often see the word “sterilized” on the package. This means that the manufacturer of the mix has heated the soil past the point of survival for many bacteria and harmful pathogens.

Although the name sounds fancy, a seed starting mix is simply a specific mixture of soil that is designed to give seeds their best chance at germinating and growing into healthy young seedlings.

How is Potting Mix Different From Seed Starting Mix?

You’ve probably heard of potting mix before — it’s a staple for flowers, veggies, raised beds…basically any type of gardening.

The best seedling mixes are lightweight but still retain water well. They’ll include either vermiculite or perlite for aeration, and either sphagnum peat moss or coconut coir for water retention.

When it comes to seedling mix, my personal opinion is that it doesn’t matter much if you choose organic vs. conventional. Think about it – you’ve got peat moss, coco coir, perlite, and vermiculite making up the majority of the ingredients. Most of these are naturally-occurring materials that by definition are “organic” because they’re minerals. They can’t be produced in a more organic manner than they already are!

I use sunshine #4 (Soilless mix) for starting, and i cut my Ocean Forest with Sunshine #4 for vegging.

2 parts Sunshine #4
1 part Ocean Forest (Happy Frog works great too)
Mycorrhizal fungi inoculant
Earthworm castings.
Dried Kelp
Jamaican Bat Poop (In the flowering mix)

The flowering mix is the same except that i add High Phosphorus Guano, in my case, Jamaican.

That mix lightens up the Ocean Forest, and improves drainage because of all the perlite in Sunshine #4. The Myco inoculant is already in Happy Frog, but it’s not in Ocean Forest, so i add it. The Jamaican Bat Guano increases the phosphorus, because i’ve always thought that Ocean Forest just didn’t have enough Phos to finish up the buds. You’ll still need the occasional Micro-nutrient.

Home grower’s guide to the best soil for cannabis.

Perlite is the most widely used soil amendment. Perlite consists of very light, bright-white rocks that greatly improve the drainage and airiness of the soil. Perlite also has decent water retention. To amend your soil with it, add 10–15% of perlite. You can add more, but then your soil may become too light and nutrients may leach out. Good-quality commercial soils often come with added perlite.


One factor to consider when choosing the right soil for your weed is whether you’re growing photoperiod or autoflowering plants. Autoflowers prefer a light mix with fewer added nutrients. A great substrate for your autoflowering ladies is a 50:50 mix of coco coir and a light, peat-based soil with some added perlite for drainage.

Sandy soil is coarse with good drainage, but has poor water retention. When watered, nutrients such as nitrogen will also quickly get washed away. Sandy soil is easy to work with and is a viable choice for cannabis growers.

If you’re growing without additional nutrients, your soil needs to contain organic substances such as humus, compost, worm castings, guano, etc. Microorganisms in the soil will turn these substances into nutrients for your plants to access on demand.