Choosing the Right Growing Medium

To say your plants get nothing from an inert growing medium isn't exactly true. Growing medium facilitates oxygenation, aids in moisture and nutrient retention, and supports your plants structurally, too. When it comes to getting results, choosing the right hydroponics medium for your particular system and crops can mean the difference between so-so and spectacular.

You'll probably discover that several manmade and organic growing media will fit your needs. In that case, price, availability, and ease of use may be deciding factors. Additionally, some media are more environmentally friendly than others. Here's a look at some different types of growing media, their benefits, drawbacks, and various uses to help take the confusion out of choosing just the right one.

Rockwool

Rockwool—spun glass wool made of volcanic rock—comes in all shapes and sizes and is one of the most popular growing media. Very convenient and versatile, this medium retains air and water incredibly well and will afford strong structural support to your plants. Rockwool typically has a high pH level which can cause pH shifts in your nutrient solution. As such, this medium does require a 24-hour pre-soaking period. Although rockwool cubes and slabs do not biodegrade, they are seldom reused. Rockwool works well in NFT, drip, and Ebb and Flow systems.

Expanded Clay Pellets

Unlike rockwool, expanded clay pellets are easy to reuse crop after crop. The porous clay pebbles offer strong support for larger plants such as tomatoes, cucumbers, and peppers. Because expanded clay pellets provide plenty of airspace, plant roots stay healthy and oxygen-rich. This medium won't react with nutrient solutions and works well in Aeroponics systems as well as NFT, drip, and Ebb and Flow systems. Finally, expanded clay pellets come in many sizes—and even different colors!—to suit your needs.

Coconut Fiber

Coconut fiber is gaining in popularity because it is biodegradable, durable, rot resistant, and very versatile. Made of compressed, shredded coconut shell fibers, this medium comes in a few different forms. As a result, the use of coconut fiber is not limited to hydroponics. Traditional gardeners sometimes add loose, shredded coconut fiber to soil in place of peat moss; others use shredded coconut fiber as straight mulch. Some hydroponic gardeners top their rockwool with shredded coconut fiber to better retain moisture.

In lieu of shredded material, washed, pressed slabs of coconut fiber are commonly used in drip or Ebb and Flow hydroponic systems. Bricked or cubed coconut fiber work well for plant propagation. Because cubed coconut fiber maintains its structure so well, it can be reused, and after use, coconut cubes and slabs can be broken down and used to amend soil. Also, this medium is so absorbent you may want to use extra ventilation.

Soilless Mixes

Perlite and vermiculite are used by themselves or in combination with other soil additives such as coarse sand or peat as soilless mixes for non-recovery drip hydroponics and passive hydroponic wicking systems. Like other growing media, soilless mixes are inert; in other words, they are non-reactive and do not directly provide nutrients to your plants. Typically, soilless mixes are inexpensive and have a near-neutral pH.

Both perlite and vermiculite are great for lightweight plants such as lettuce because they do not crush fine stems and delicate root systems. Soilless mixes containing an even mixture of both are very popular because, while vermiculite retains moisture well, perlite allows for adequate oxygenation. Both of these mined components are reusable.