Posted on

best medium to grow cannabis in

Best medium to grow cannabis in

Example of flowering DWC cannabis plants. They grow so quickly that they can quickly take over your grow room!

About Less Common Types of Hydro: Some people grow with plant roots suspended in misted air (aeroponics), in an assembly line (NFT), or in a tank with fish (aquaponics), but these are better suited to smaller plants, and not commonly used to grow cannabis.

Allow me to explain…

Conclusion: What’s the Best Grow Medium for Growing Cannabis?

Soil or compost is one of the most popular growing mediums for marijuana plants because it is natural, easy to use, and available everywhere.

When growing in a soilless medium, you can treat your plants almost the same as if growing in soil. The main difference is you feed all their nutrients in the water. As a result of your plants getting nutrients delivered directly to their roots, you will often get quicker growth and higher yields than growing in soil (where the roots have to seek out nutrition).

Best of the Best: Grow Medium Roundup

Two hydroponic cannabis plants in the vegetative stage

Although there are many different possible soilless ingredients, the most popular potting mixes for cannabis contain significant amounts of coco coir and perlite. This combination seems to work especially well for growing cannabis. As a result of coco’s growing popularity, other types of soilless mixes (especially the peat-based ones) have become far less common in cannabis grow rooms over the years.

Best medium to grow cannabis in

Most commonly known as Rockwool (a brand name), mineral wool is an extremely popular medium for rooting and growing plants, especially in heavy hydroponic systems. Spun from fibers created by melting various rock types, the “wool” is then pressed into various plugs, squares and slabs for growing plants. Mineral wool will hold a considerable amount of water while also allowing for good air permeation. Mineral wool is sterile and inert with a neutral pH, however, it has poor buffering and is generally regarded as a medium for advanced growers.

Similar to vermiculite and perlite, clay can be heated and expanded. However, with clay, the medium becomes much harder after heating. Still, the clay aggregate is porous enough to give it some decent water-holding ability, though not enough for systems using a single daily watering. Rather, this medium is better suited for continuous-flow or multiple-watering hydroponic systems. Inert and sterile with neutral pH, HEC offers little to no buffering properties, but it is highly stable and capable of holding seedling or clone plugs in active hydro systems. HEC can also be used as a bottom layer for drainage in plant containers or as a mixed-in additive for soilless mixtures.

There are three types of peat used in agriculture: peat moss, reed sedge and peat humus. Peat moss is the most widely used and is derived from sphagnum and other mosses, varying in color from tan to dark brown. Peat has a high moisture-retaining capacity, being able to hold 15 times its dry weight in H2O, and contains small amounts of nitrogen. However, it has high acidity with a pH range of 3.2 to 4.5. Peat is almost always used in soilless mixtures, rather than as a stand-alone medium, with sphagnum, perlite, wood chips and coco being its primary partners.

A gray-white mineral mined from volcanic lava flows, perlite is also heated and expanded into small, sponge-like kernels that are extremely lightweight with decent water-retention properties of three to four times its dry weight. Its best feature is that it is very neutral with a pH of 6.0 to 8.0. Unlike vermiculite, perlite has no cation exchange capacity and therefore is poor in buffering. This is why perlite is often used as a spread on top of soilless mediums to help keep moisture locked in below.

Hardened Expanded Clay (HEC)

To start, whenever discussing indoor grow mediums, I think it is important to differentiate between “soil” and “soilless” mediums. When we, as growers, talk about using soil indoors, we are actually talking about what is commonly known as “soilless” mediums.

Chemically speaking, vermiculite is hydrated magnesium-aluminum-iron silicate. It expands quite a bit when heated, and once expanded, it is extremely lightweight. It is insoluble in water, inert and can absorb huge amounts of water, which is why it is often a key ingredient in soilless mixes. Furthermore, its high cation exchange capacity makes it very good for buffering and use with heavy nutrient programs.

Thanks for writing in Carlos & Melinda—and congratulations on starting your first grow! That is music to our ears here at High Times!

Perlite

For those with previous experience looking to use a hydroponic system, soilless mixtures are still good for top-feed or drip-irrigation systems. Once you move into the more advanced hydro setups, such as flood-and-drain tables, deep-water culture (DWC) or nutrient film technique (NFT), mineral wool and HEC become better choices.

Very similar to peat moss, sphagnum is a moss composed of dehydrated acid-bog plants. Being perhaps the most desired moss for agricultural use, it is expensive to produce and as such, it is often used in soilless mixtures alongside peat moss. Sphagnum has very high water-absorbing properties and can absorb 10 to 20 times its dry weight in moisture. Sphagnum moss has a pH between 3.5 and 4.0. Much like peat, sphagnum offers excellent buffering qualities for the root structure, helping to prevent nutrient burn and making it very forgiving for beginner growers.