Grow Medium Guide For Indoor Growers

Are you a novice hashish cultivator on the lookout for a information to develop mediums for indoor marijuana rising? Well, you’re in luck. High Times Cultivation Editor Nico Escondido solutions your whole develop questions in his weekly Nico’s Nuggets column, and this week, he’s specializing in develop mediums for indoor growers.

The Question: What Grow Medium Is Best For New Indoor Growers?

Dear Nico,

Long-time reader, first-time grower right here! As my spouse and I start our journey in rising, I needed to get your tackle the abundance of indoor develop mediums presently obtainable available on the market. As first time growers, we’re leaning in the direction of utilizing soil and hand-watering the crops, as I’ve seen you advocate this strategy for novices a number of occasions through the years. However, we’re open to doing a hydro system if the medium and system are straightforward sufficient to deal with. Any recommendation is far appreciated!

— Carlos & Melinda, by way of the mailbag at

The Answer: The Most Popular Grow Mediums For Indoor Growing

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

To begin, each time discussing indoor develop mediums, I feel it is very important differentiate between “soil” and “soilless” mediums. When we, as growers, speak about utilizing soil indoors, we are literally speaking about what is usually generally known as “soilless” mediums.

Grow Medium Guide for Indoor Growers

Correct medium decisions assist genetics attain their potential as seen with this pink Jah Goo.

Actual mineral soil or topsoil is never, if ever, used indoors anymore (excluding greenhouse grows). This is just because there at the moment are higher choices that may do the identical factor as mineral soil. These “soilless” mixtures are peat- or sphagnum-based. When one considers that actual earth soil is usually not bought as a sterilized medium and should include pests, molds or potential illnesses/viruses embedded in it, the danger of bringing that into an indoor backyard is just not value it—particularly when these moss-based mediums look, really feel and act similar to precise soil.

That being stated, let’s take a fast take a look at a number of of the preferred mediums for indoor gardens:


There are three forms of peat utilized in agriculture: peat moss, reed sedge and peat humus. Peat moss is probably the most extensively used and is derived from sphagnum and different mosses, various in colour from tan to darkish brown. Peat has a excessive moisture-retaining capability, with the ability to maintain 15 occasions its dry weight in H2O, and incorporates small quantities of nitrogen. However, it has excessive acidity with a pH vary of three.2 to four.5. Peat is nearly all the time utilized in soilless mixtures, moderately than as a stand-alone medium, with sphagnum, perlite, wooden chips and coco being its main companions.


Very just like peat moss, sphagnum is a moss composed of dehydrated acid-bog crops. Being maybe probably the most desired moss for agricultural use, it’s costly to supply and as such, it’s typically utilized in soilless mixtures alongside peat moss. Sphagnum has very excessive water-absorbing properties and may take in 10 to 20 occasions its dry weight in moisture. Sphagnum moss has a pH between three.5 and Much like peat, sphagnum gives wonderful buffering qualities for the basis construction, serving to to stop nutrient burn and making it very forgiving for newbie growers.

Grow Medium Guide for Indoor Growers

A soilless, peat-based combination with perlite combined in.


Chemically talking, vermiculite is hydrated magnesium-aluminum-iron silicate. It expands fairly a bit when heated, and as soon as expanded, this can be very light-weight. It is insoluble in water, inert and may take up big quantities of water, which is why it’s typically a key ingredient in soilless mixes. Furthermore, its excessive cation change capability makes it excellent for buffering and use with heavy nutrient packages.


A gray-white mineral mined from volcanic lava flows, perlite can also be heated and expanded into small, sponge-like kernels which might be extraordinarily light-weight with respectable water-retention properties of three to 4 occasions its dry weight. Its greatest function is that it is rather impartial with a pH of to Unlike vermiculite, perlite has no cation change capability and subsequently is poor in buffering. This is why perlite is usually used as a variety on prime of soilless mediums to assist hold moisture locked in under.

Hardened Expanded Clay (HEC)

Similar to vermiculite and perlite, clay might be heated and expanded. However, with clay, the medium turns into a lot more durable after heating. Still, the clay combination is porous sufficient to offer it some respectable water-holding capacity, although not sufficient for methods utilizing a single day by day watering. Rather, this medium is best fitted to continuous-flow or multiple-watering hydroponic methods. Inert and sterile with impartial pH, HEC presents little to no buffering properties, however it’s extremely secure and able to holding seedling or clone plugs in lively hydro methods. HEC may also be used as a backside layer for drainage in plant containers or as a mixed-in additive for soilless mixtures.

Grow Medium Guide for Indoor Growers

Hardened expanded clay (HEC) being utilized in a flood-and-drain hydro desk.

Mineral Wool

Most generally referred to as Rockwool (a model identify), mineral wool is a particularly in style medium for rooting and rising crops, particularly in heavy hydroponic techniques. Spun from fibers created by melting numerous rock varieties, the “wool” is then pressed into numerous plugs, squares and slabs for rising crops. Mineral wool will maintain a substantial quantity of water whereas additionally permitting for good air permeation. Mineral wool is sterile and inert with a impartial pH, nevertheless, it has poor buffering and is usually considered a medium for superior growers.

Coconut Fiber/Coir

Often referred to easily as “coco,” coconut fiber can are available quite a lot of varieties together with shredded fibers, small cubes or a finer, extra granular medium. Coco is usually combined into soilless mixtures with peat and vermiculite, however it can be used as a stand-alone medium for potted crops. Derived from coconut husks, coco is sterile and has good water-retention and buffering properties.

Obviously, selecting one of many above mediums hinges so much on the kind of develop system getting used within the backyard. In phrases of the query posed, I might concur that for a first-time grower, utilizing a soilless combine (resembling Sunshine #four or Pro-Mix) and using a every day hand-watering regiment is the best choice.

For these with earlier expertise wanting to make use of a hydroponic system, soilless mixtures are nonetheless good for top-feed or drip-irrigation techniques. Once you progress into the extra superior hydro setups, akin to flood-and-drain tables, deep-water tradition (DWC) or nutrient movie method (NFT), mineral wool and HEC grow to be higher decisions.

Remember, whichever method you go, make sure your root zone is definitely permeated by air in order that roots can get the oxygen they love a lot. And relating to buffering and selecting your nutrient program keep in mind—much less is extra, as you possibly can all the time up your dosages, however correcting a nutrient overload is rather more troublesome.


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