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How to Grow Cannabis in Soil
by Nebula Haze
Intro to Growing Cannabis in Soil
Growing plants in soil seems to be what many people try first when it comes to growing in cannabis. If you’ve grown other plants in soil and/or have maintained a soil garden, this may be the best choice for you because you will already be familiar with a lot of what you need to understand to grow cannabis in soil.
Note: 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 burn your cannabis plants in the flowering/budding stage and reduce your overall yields.
Soil Pros for Growing Cannabis
Many Already Have Soil Experience - Growing cannabis in soil is similar to growing plants like tomatoes or corn - soil growing may be the most intuitive option for you, especially if you already have gardening experience.
Simple - hand-water your plants in containers
Outdoor Growing - most outdoor growers choose to grow with soil. In the wild, cannabis grows in soil, so growing outdoors in soil is most like a cannabis plant's natural environment. Many people find that when growing cannabis outdoors, soil is the simplest and most intuitive way to grow. Growing with composted "super soil" gives the grower the ability to grow outside without needing to add synthetic bottled nutrients or manage the pH of the soil.
Option 1: Store-Bought Soil + Nutrients - Growers can buy soil online or at a store, and simply add nutrients throughout their grow while watering for thriving, happy cannabis plants.
Option 2: Compost or Purchase "Super Soil" - For those who don’t want to worry about soil pH or adding nutrients throughout the grow, there is the option of amending and composting your own super soil (or buying it already composted) specifically made for cannabis plants. While this option takes more time before you start growing, it can be somewhat simpler especially for those who have composted soil in the past. Note: Some growers believe growing in organic composted super soil with a rich microbial life actually improves the taste and smell of cannabis by causing plant to produce higher levels of terpenes and terpenoids.
Soil Cons for Growing Cannabis
Pests - Soil is organic material, and there are many types of bugs that can live in soil. Often, soil-growers seem to suffer more often from pests attacking their plants than hydroponic growers.
Slower Growth - Growing in soil is not as fast as growing in a soilless or hydroponic setup - hydroponic plants tend to get better growth rates, especially in the vegetative stage.
Get Soil and a Container for Your Cannabis Plants
- Common cannabis soil mixes include Fox Farms Happy Frog and Fox Farms Ocean Forest. Any high quality organic soil mix will do in a pinch.
- Avoid Miracle-Gro soil or anything with “extended release” nutrients!
- To improve drainage, it can be beneficial to add 30% perlite to aerate and loosen soil.
- Common cannabis containers include classic plastic pots, terra cotta pots, smart pots (fabric pots) and air-pots. Learn more about different types of containers
Not sure which soil should you start with? I recommend starting with Fox Farms Happy Frog soil and mixing the soil with about 30-40% perlite for a perfect cannabis soil starting mix. For the easiest soil growing, get a smart pot (a growing container made out of fabric - they work perfectly for growing cannabis).
Don't want to use nutrients? Learn how to mix up your own super soil so it has all the nutrients your cannabis plants will need! Bonus: With composted super soil made using the recipe in the link above, you don't need to worry about maintaining your pH! your super soil will automatically manage the pH for you.
Maintenance Cost - After setup, the main maintenance will be replacing your soil every grow (highly recommended - reused soil often does not get great results even with added nutrients). Occasionally you will have to replace used containers that crack or break. You also need to think about the cost of electricity and replacing nutrients every few grows.
Maintenance Effort - Watering your plants, providing nutrients and managing the pH to prevent deficiencies (composted super soil which has microorganisms in your soil to help manage pH and make nutrients available to your plant roots).
How long until harvest? Soil has relatively slower growth rates than hydroponic methods, but a tuned-in soil grow can achieve impressive growth rates if given a great environment and plenty of bright light. Most soil grows require 1-3 months of vegetative time (depending on how big you want your plants) plus 2-3 months of flowering/budding (depending on your strain).
Many growers feel that cannabis grown in organic super soil has the best smell/taste profile, though this is highly disputed among hydroponic growers :)
How long can grower be away? It’s important for a grower to always remain close by for their first grow, especially for inexperienced growers. Experienced growers can safely spend more time away from the garden.
Bigger containers hold more water and therefore give growers more time away, since constant watering isn’t needed. In the best case scenario it is always best to check on your plants at least once a day. You never know when a pest infestation will take hold, a plant will fall over, or some other unexpected event will happen.
Most Common Soil Mistake: Overwatering
The most common mistake made by beginners growing cannabis in soil is they water their plants too often. Overwatering is almost never a case of giving your plants too much water at once. Instead, overwatering cannabis in soil is almost always caused by giving the plant water too often.
How to water cannabis plants in soil
Wait until the top of your soil feels dry up to your first knuckle (about an inch deep)
Add nutrients to your water (if needed), then adjust the pH. The most common reason growers get nutrient deficiencies is because they don't adjust the pH of their water. Most soil growers only add nutrients every other watering (or even less often), but even when giving just plain water you still need to adjust the pH of your water to prevent deficiencies.
Start watering your plants and continue to add water until you see at least 20% extra runoff water drain out the bottom of your pot. Go back to step 1.
Cannabis-Friendly Soil Nutrient Suggestions
For new nutrients you haven't grown with before, always start at half-strength and raise the amount slowly. Do not use nutrients with every watering! Most growers will add nutrients every other watering or even less frequently. Remember, a little bit goes a long way. You can always add more nutrient later, but it's a lot more difficult to take them back from the soil.
An easy and simple nutrient systems that for beginning cannabis growers in soil is the Fox Farms Nutrient Trio for Soil.
The Fox Farms trio works great for growing any cannabis strain, without needing any additional supplements.
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.
Make sure you get the soil version if growing in soil, because Fox Farms offers a hydroponic version of the same nutrient line.
Nutrient Picks for Growing in Soil
Fox Farms Nutrient Trio for Soil <-- Very concentrated, less is more. "Grow Big" & "Tiger Bloom" provide most of the major nutrients your cannabis needs, while "Big Bloom" has many micro nutrients and beneficial compounds that help nutrient uptake and root health. This trio works extremely well by itself, just follow the feeding schedule (here's a PDF, here's a JPG) from Fox Farms. They offer a lot of supplements, but the only bottles you need to be successful growing cannabis is the FF trio, which is highlighted in green on the schedule. The trio tends to be strong, so use it sparingly (especially "Grow Big" & "Tiger Bloom"). I recommend giving plain pH'ed water every other watering to make sure your plants only get exactly what they need.
Botanicare Pure Blend for Soil (Soil 2-pack for the Vegetative & Flowering Stage) <-- Recommended for Beginners becuase this nutrient system is easy to use, relatively cheap, and can be found at almost any hydro store or online. Botanicare Pure Blend for Soil works great for growing any cannabis strain, without needing a lot of extra care, or any additional supplements. The two bottles are all that's needed to get your plants successfully to harvest time. You can follow the instructions on the bottle or use the feeding schedule from Botanicare (here's a PDF, here's a JPG). They offer a lot of supplements, but the only bottles you need to be successful growing cannabis is the Pure Blend 2-pack, which is what's reflected in the "standard" version of their schedule. Repeat "Week 3" of the Vegetative part of their schedule until the end of the vegetative stage if it lasts longer than 3 weeks. Forauto-flowering strains - skip week 3 of "Vegetative" & skip week 6-7 of "Flowering/Fruiting" - otherwise you can follow the instructions almost exactly.
Dyna-Gro (Foliage-Pro, Bloom) <-- Cheapest nutrients that still work great for growing cannabis in soil. Use "Foliage-Pro" during the vegetative stage, and "Bloom" during the flowering stage. Just follow the instructions on the bottles!
HydroOrganics Earth Juice Nutrients (Grow, Bloom) with the followingsupplements: Earth Juice Catalyst, Meta-K, MicroBlast & Hygrozyme (use as needed for roots) <-- From a grower: “Earth juice Grow/Bloom is organic stuff, veddy potent and cheap.”
This nutrient schedule was used to grow the following buds under a 250W LED.
House & Garden Line-up (expensive yet remarkably effective) Soil A + B, Roots Excelurator, Algen Extract, Bud XL, shooting powder. <-- Get a custom nutrient schedule directly from the people at House & Garden via their free online nutrient calculator.
From a grower: “H&G was started by a top researcher from Canna. They are right outside of Amsterdam and because cannabis is legal there, so both Canna and H&G are able to do R&D using cannabis. I don't know about Canna, but I know that House and Garden makes all their own nutrients in house and they work great.”
This plant was grown using the House & Garden Line-up listed above
Don't want to use nutrients? Learn how to mix up your own super soil so it has all the nutrients your plants need! Bonus: With composted super soil, you don't need to worry about maintaining your pH! Instead, you are actually creating a specially made microbial soil mix that will automatically take care of the pH for your plants, while slowly feeding them the exact nutrients they need.
Many of us have seen Miracle-Gro used around our homes, so we know that it works for ‘regular houseplants’. Cannabis is just a tough weed, so Miracle-Gro nutrients should work great for it, too... right?
No. Not really. Well kinda.
Standard Miracle-Gro nutrients (their all-purpose plant food) will work "just okay" for the vegetative stage of your plants growth, but anything with Miracle-Gro in it is a terrible choice for the flowering stage due to its high levels of Nitrogen. Using standard Miracle-Gro nutrients in the flowering stage will cause your buds to grow smaller than they could have.
However, the real problem is Miracle-Gro's "time released" soil (or any type of extended release spikes or soils) which slowly release Miracle-Gro nutrients over the course of several months. These types of soil continue providing Nitrogen slowly throughout your plant's life. That means your plant won't be able to use up all the Nitrogen in the vegetative stage like it would with regular soil, again giving you the problem of too much Nitrogen in the flowering stage.
Basically, avoid giving your plants a lot of Nitrogen in the flowering stage! Anything that does that is not a good idea :)