Happy mediums

The growing medium is of paramount importance to your plants’ health and success. Different mediums have varied advantages and disadvantages. You should decide what medium to use based on the specifics of your needs and your grow situation. Read on for an outline of the pros and cons of each medium.

A good place to start is with the traditional almost-hydroponic medium ? peat. Peat is a great moisture holder. It is inexpensive and you can get it just about anywhere. However, it is prone to slime molds, and insects seem to thrive in the tiny crevasses on the surface. It’s also not always of the greatest quality and it’s a common thing to see rogue little shoots growing from naturally occurring seeds that have made it through the purification process.

You would normally mix peat with perlite to increase its moisture-holding capability. This also makes the growing medium less dense yet still substantial enough to support the plant, thus promoting good root growth.

Peat lasts for quite a while, but is prone to jealously holding the salt accumulation that builds up after a few months. There’s just no way to get the salt out after you’ve used it. On a lighter note, peat is usually pretty tame in terms of pH. Its inertness is legendary. When you’re done with it, just throw it on the garden out back. Your veggies will love you for it.

Pea gravel

This is the method I used when I first cut my teeth in hydroponics, and I think it works great.

The clone or seed is stuck into a rockwool cube and allowed to germinate. When the roots start growing out of the sides or bottom, just place the rockwool cube on the surface of the layer of pea gravel. If a lot of the roots are growing out the sides, simply bury the rockwool cube in the gravel. The roots will find their own way into the spaces between the gravel.

Just be sure not to lift the rockwool cube to see if the roots made it into the gravel ? you’ll tear them without even realizing it, stunting your future party favors right from the beginning!

Pea gravel is very inert, but must be thoroughly cleaned and sterilized. The common method is to use one part chlorine bleach to 10 parts water. Fill whatever container your gravel is in so the liquid is above the layer of gravel. Let this soak for a day, and then rinse the solution with fresh water a few times. There should be a light scent of bleach when all is done. If you can smell that wet-dust smell of wet gravel, then you haven’t rinsed enough. Also, if you get an earthy smell you have to let it soak in bleach for another day because there’s still organic matter in the gravel somewhere. That’s a no-no.

Pea gravel is used most often with the ebb and flow technique. In ebb and flow, the nutrient solution is allowed to flow into the growing container until just above the layer of gravel. The container is then drained, leaving behind nutrient in the pea gravel. You would do this three or four times a day. Ebb and flow is a no-brainer that is probably the most widely used method out there for small personal hydro farms.


Perlite is a small, stone-like substance that is white in color. Perlite isn’t used alone; it is used to increase the moisture content of the surrounding medium. It mixes well in just about anything except pea gravel. This is because perlite is a stone-like substance; the granules tend to settle out to the bottom of the tub of pea gravel, negating their use in that situation.

In terms of inertness, perlite can’t be beat. You just rinse the stuff and apply it. It’s also fairly inexpensive and is very common. You can pick it up at any greenhouse or garden supply store.


Sand is the hydroponic medium that raises the most eyebrows. I don’t like it personally because I feel that its small grains make it harder for the root system to develop. It does, however, hold moisture extremely well, and cleans easily ? you can reuse it to your heart’s content, sifting it through a screen after each growing session. I would say the coarser the better when using sand, but that’s just me.

Sand is wonderfully inert and is obviously pretty common. It has a tendency to hold salt more than does pea gravel, so be sure to flush it with pure pH balanced water on a regular basis.

When mixed with perlite, sand is a great medium to grow in, I’m told. Just watch that it doesn’t foul any workings you might have in place to deliver your nutrient. Sand gets into everything, so if you’re burning out water pumps like crazy, you now know why.


Rockwool has been around for ages. It’s a fluffy blown glass that sucks moisture up like a sponge, and holds just the right amount. Rockwool is great stuff, and it’s the preferred medium to start seeds or clones in. It’s absolutely inert and is cheap. It is available just about anywhere in sizes ranging from 3/4 of an inch to six inches square. The smaller sizes come in foot-long square rods that you cut yourself. No special tool is required to cut it and if you make a mistake, it doesn’t matter because it is so cheap.

As with most things, there is a caveat to rockwool. Because of its moisture holding ability, rockwool is prone to slime molds and fungal infections. This can be remedied by some preventative maintenance involving a liquid fungicide. Any brand will do as all are pretty much the same as the next. The liquid holding ability of rockwool lends itself very well to this technique. You would usually apply the fungicide with any rooting hormones you normally use with clones. The fungicide sticks around for quite a while, so I’ve never had the need to apply it again after the cloning stage.

One drawback to rockwool is that it is not biodegradable, and you must replace it after each crop. Also, you must ensure it remains wet while you are using it, as when it’s dry it gives off harmful microfibers which can damage the lungs.

No medium

Not using a medium is perhaps the most challenging and unforgiving method, but the results are fantastic. I haven’t used a medium for almost six years now, and I’m getting a reputation for growing “couch glue” grass that knocks your socks off.

If you’re a hash lover, you should be growing without a medium ? if you use the buds in your shake tumbler, the screen will actually get clogged. I’ve seen it happen. We had to change to a coarser screen and spend an hour poking a pin into each hole in the fine, clogged screen to get the hash out of it.

Not using a medium frees the energy that would normally be used to grow an extensive root system. This translates into wonderful foliage, a high stem, and potent bud.

To grow this way you need to keep the roots under a continual mist of water and nutrient, and you need to keep the plant stable with no medium to root in. The plant grows so fast that the stem can buckle under the weight of the plant because stems grow so slowly. You can combat this with some preventative maintenance ? use a plastic anchor pole and tie it loosely to the stem. Add ties every three or four inches as the stem grows. Use a good solid-cored wire with a plastic sheath for this ? don’t use a cotton string or any other string that will hold moisture. The stem will rot around the string if it gets wet. Also, the smooth sheath on wire doesn?t irritate the stem or cause abrasions that will hinder growth.

Another tip: make sure the support pole goes all the way to the bottom of whatever you’re using as a reservoir. Anchor it at the bottom and at the height of the root. This will make a sturdy pole that won’t go lopsided when the plant gets heavy.

So that’s your mediums, in a nutshell. Choose the one that seems the best for your situation. Skill level is a consideration ? you don’t want to have your plants die on you, of course. A failed crop means you’ll have to buy your smokables until the next harvest.

If this is your first foray into growing your own stuff, I recommend the ebb and flow technique using pea gravel as a medium. You can’t go wrong with that one.

Good luck and happy growing!