Avoid Miracle-Gro! Do not use “Miracle-Gro” soil or any soil that has “extended-release” nutrients for growing cannabis. These types of soil will continue to release nitrogen to your plant roots for up to 6 months. This can cause deficiencies or burn your cannabis plants in the flowering/budding stage, reducing your overall yields. I have seen growers successively grow cannabis in Miracle-Gro, but many of them struggled with nutrient problems in the flowering stage.
There are three different bottles that you will need to grow cannabis, “Grow Big,” “Big Bloom,” and “Tiger Bloom.” They are often sold together. Simply follow the included nutrient schedule (here’s a PDF, here’s a JPG) from Fox Farms.
Soil growing probably requires the least effort of any growing method (especially if growing in super soil). Your main effort will be spent watering your plants.
I don’t do it with cannabis seeds, but I’ve done it with corn, tomatoes, peas, and a bunch of other fruits and veggies. The only reason I don’t do it with cannabis seeds is because I typically don’t get 100% germination doing it that way. Instead I normally get a 60%-80% success rate and then if I’m sowing directly outside before the season has started (e.g. winter sowing) sometimes I come back a few days post germination only to discover some insect or small animal chewed my seedling in half.
For me it’s easier and more reliable to buy a bag of sterilized potting soil made specifically for seed germination and start my seeds indoors, then let them grow out for at 3-4 weeks or until the stem gets about as thick as a #2 pencil. Its a little more work and it also means I have to spend 3-5 days hardening them off outdoors, but the survivability is so much higher that it’s worth it.