It’s said that you are what you eat. The same goes for plants. Cannabis gets most of its power from the sun, but it’s literally made from the nutrients it can draw from whatever it’s growing in. It’s the difference between the gas that runs your car and the steel and rubber than make up the car itself.
When you’re growing your own cannabis, you want it to grow efficiently and healthily. Once you have your lighting situation figured out, the grow medium is the most important aspect of your cannabis growth. It may be even more important since you can easily change a lighting setup even after your plants are sprouted.
There are a lot of grow medium options on the market, and all of them have their benefits and drawbacks. Let’s explore these options.
How to Choose and Use Grow Mediums
The first step to choosing a grow medium is understanding where each medium shines.
This is the tried-and-true original method. Soil is where cannabis plants grow in the wild, obviously. If you live in a place where the climate encourages cannabis growth, you can till up a garden patch in your backyard and potentially have a great cannabis harvest. There’s so much more to soil than just your average backyard dirt, however.
Today, you can purchase soil that’s already amended with things like fertilizers and compost to give your plants a boost from the beginning. Even with amendments, soil is frequently one of the cheapest and easiest grow mediums to get. It’s used for basically every plant and garden, and you can often buy it by the cubic yard from garden supply stores.
There are a couple of downsides to soil. First, it’s the most difficult grow medium to move. Pots of soil are heavy, and if you’re growing outside, you’re more or less locked into your plants’ location. Soil is also difficult to flush if you over-fertilize, so you are at a higher risk of nutrient burn or lockout. Finally, just as cannabis evolved for soil, bugs evolved to hide in soil. It’s harder to treat pest infestations in soil, because they can hide more effectively.
How to Use Soil Effectively
Planting in soil is intuitive for most people. You simply place a seed or clone plant carefully into a pot of dirt, water it when the top two inches of soil are dry, and fertilize as necessary – and boom, done. If you’re using un-amended soil, you do need to fertilize regularly with a blend designed for cannabis. If you want to use a soil that comes with fertilizers already mixed in, you may still need to supplement nutrients. Be sure to read the packaging to see its blend, so that you’ll know what you need to add or avoid adding.
Avoid using MiracleGro or other “slow-release” soils. They are designed to provide extra nitrogen for up to half a year. That can result in nutrient burn or lockout in your cannabis plants, especially if you’re supplementing other nutrients. Instead, look for soils designed for outdoor gardens instead of houseplants. Those work better for plants intended for harvest.
Once you have your plants in soil, you can work on developing your own compost if you want. Compost is made by allowing organic materials to decompose down into rich black dirt. This takes time, but if you plan on growing multiple harvests, your food scraps and old cannabis stalks can feed your future cannabis crops.
Transplanting is easy with soil. When the plant’s roots start to grow out the bottom of the container, fill the new container up so that the new coir plus the original coir come to the top of the new container. Place the original coir in the new container without disturbing the roots, and fill in around it.
Hydroponic growing covers a lot of different methods. It can be as simple as a timed watering system attached to some coco coir pots to a complex collection of pumps, tubes, and drains that constantly push water and air through different planters. The basic description of a hydroponic system is one in which plants are grown in an inert substance and nutrients are provided through the water.
Hydroponic systems cut down on daily labor, but they take time and financial investment upfront. The most basic ones require at minimum a timer, fertilizer solution, pumps, and water hoses. Entire kits can be bought that take the thinking out of it, or you can look up DIY blueprints that involve everything from PVC to bamboo.
How to Use Hydro Effectively
First, consider your budget and your available space. Setting up a hydroponic system doesn’t have to be expensive, but DIY systems take time to set up without resulting in leaks. It can be worth it, if you’re looking to fine-tune your grows, or if you grow a lot of plants at once.
Coco coir is literally ground up coconut and palm husks. It’s a fluffy brown mixture without any inherent nutrients, similar to peat moss. It can be used on its own, or as a soil amendment.
If you like the idea of growing in soil but want precise control over your plants’ nutrients, coco coir is a great option. Coir is great at holding nutrients and water, and cannabis roots can grow through it quickly. It’s completely biodegradable and doesn’t attract bugs.
The downside of coco coir is that you constantly have to fertilize your plants, from the beginning. This can be labor-intensive if you don’t want to buy a specific fertilizer mix. Other than that, it’s a good half-way point between soil and true hydroponic growing.
How to Use Coco Coir Effectively
Plant your cannabis plants the same way you would in soil. Water regularly, checking to make sure the first inch or two of coir is dry. Fertilize regularly and thoroughly – remember that the only nutrients your plants will come from what you add.
You can also mix coco coir into the soil, or amend coir with something like perlite. Good ratios are 70% soil to 30% coir, or 70% coir to 30% perlite. These encourage drainage while maintaining nutrient retention and aeration. Transplanting in coco coir works like transplanting in soil – remember to be careful with the roots.
Lastly, you can use coco coir to anchor roots in an automatic hydroponic system. The coir protects roots and gives the plants something to anchor themselves in. Coir does have to be replaced occasionally since as an organic material it degrades over time.
Rockwool is a material made of basalt rock, heated to incredible temperatures and spun out like cotton candy. As a completely inorganic material, it has no nutrients. It is not biodegradable. However, this makes it an ideal medium for anchoring plants in a hydroponic system.
A big downside of Rockwool is that without treatment, it is very alkaline. It requires soaking in an acidic nutrient bath for a day before use in order to balance this out. It is also difficult to reuse since it comes in a slab and is not loose like coir.
How to Use Rockwool Effectively
Sprout cannabis seeds between two damp paper towels. Once a root has appeared, carefully poke a small hole in the top of a Rockwool cube and place the seedling into the cube, root down. Remember that fertilization through the hydroponic system must start immediately.
When you need to transplant into a larger piece of Rockwool, cut a cube the size of the plant’s current piece of Rockwool out of a larger slab. Gently place the current piece into the hole in the new piece, and the plant will root itself into the new piece.
Perlite is a great soil amendment or hydro medium. If you’ve ever bought potting mix, the little white pellets in it are usually perlite. It is perfect for improving drainage, since it doesn’t absorb water. It is also full of tiny holes, which allow it to hold onto nutrients. It’s not ideal as a medium on its own, however, because it drains so quickly that plants don’t have time to absorb the water. Mix 30% perlite into soil or coir for a drainage boost, or place the cannabis seedlings in perlite for hydro systems where roots are submerged regularly.
Types of Growing Containers
There are a few basic types of pots available. What works best for you depends on your climate and budget for your cannabis garden.
Ceramic pots are made of clay or terracotta. These encourage drainage, as water can evaporate through the pot. In humid climates, ceramic pots are great. However, they are heavy, and in dry climates, they can lead to your plants withering if you don’t water frequently. They are reusable unless your plants catch a disease. Then they can transfer that disease to your next crop because they are difficult to sterilize.
Plastic pots are cheap and light. However, they are impermeable, so overwatering is a greater danger. This can lead to root rot or pest infestations. They can be reused almost infinitely, as long as they don’t crack.
Fabric bags are lightest of all. You can even plant your cannabis in burlap sacks full of your chosen grow medium. Bags are light and encourage root growth by allowing air into the pot. They also encourage evaporation. However, most bags are biodegradable, which means that they can decompose and potentially rip if left too wet or simply used too many times.
One thing to keep in mind is that plants in soil benefit from repotting at least once, if not twice during their growth. Cannabis plants grow very quickly, but seedlings benefit from small pots in the beginning.
Small (One Pint)
Whether you sprout your seeds in between moist paper towels or in the pot itself, seedlings grow best in pots about a pint or less. Small pots dry out more quickly, which is actually a benefit for seedlings without developed root systems. It brings air to the roots, which encourages growth. Once the roots become visible at the edge of the container or through drainage holes, move plants to a bigger container.
Medium (Two to Five Gallons)
A medium pot can work forever for smaller cannabis strains. This size allows plants to get up to about three feet high comfortably. If you’re looking to limit the size of a plant, keep your plants in a medium container permanently.
Large (Five to Ten Gallons)
In cases where the strain is known to get very large, or where a grower wants to transplant twice, a large container is great. A second transplant allows for cannabis to make the most of its flowering stretch. A week or two before you intend to switch to the flowering phase, transplant your cannabis into its final pot. This allows the plant to recover from shock before the flowering stage.
Growing cannabis doesn’t have to be complicated. After all, it grows like a weed. The real trick is maximizing your harvest, so the time and effort you put in is rewarded. Start your plants off on the right foot by putting them in the right grow medium at the start of your grow.