Greenhouse Canada

Features Growing Media Inputs
The complexities of managing the media

June 7, 2017  By Gary Jones

July 2017 – Over the past few years, Kwantlen Polytechnic University students have been working with local schools (elementary, middle and high schools) to help design gardens. In each case, it has been at the school’s request. This is critical, since it means they have ownership and therefore (hopefully!) commitment. Plans have been driven by specific constraints of the spaces available and any wants/needs of the school community, and these needs were in turn identified by doing surveys of all stakeholders.

Ideas usually include seating areas, lunch tables, grassed areas, (fruit) trees, compost space and storage. As well as food growing spaces, there is always a strong desire for flowers. Due to most school gardens being put in spaces that are currently paved, or are simply muddy areas, growing places inevitably end up utilizing raised boxes/beds that need filling with growing media.

Schools often therefore ask “where do we get soil?” (That said, one school actually dug up a big section of the asphalt parking lot, so soil was not their most immediate purchase!) There are several suppliers of great quality manufactured media in the Lower Mainland, and many of these will do a good deal for projects like school gardens. These are the gardeners of the future after all!


Students and teachers then want guidelines for managing these soils. “Water not too much or not too little, until it’s just right…” isn’t enough. And if schools can get this right during term time, there’s always the prickly subject of who is going to look after the garden during summer? This is precisely why schools must take ownership of their garden right from the start! Timers always help, but then plants get watered on set schedules irrespective of actual water requirements.

Once planted and growing, raised beds need to have some management of crop nutrients, providing students an opportunity to learn about chemistry. This fits well with the new experiential learning curriculum of the B.C. education system.

Further, we need to manage the biology of the rootzone – worms, organic matter content, insect pests, beneficials, etc. Often this can lead to discussions around the relative merits of soil-based media compared to, say, hydroponics.

On the other side of the horticulture coin, a number of schools have student groups building their own small-scale aquaponics systems. That itself leads to the complex debate around the possibility of certified organic hydroponic production, particularly in the U.S., which “is one of the few countries that allows hydroponics to be labeled organic. Mexico, Canada, Japan, New Zealand, and 24 European countries (including Holland, England, Germany, Italy, France, and Spain) all prohibit hydroponic vegetable production to be sold as organic in their own countries. This means ‘organic’ hydroponic producers in other countries are often growing exclusively for a U.S. market.”1

In fact, the U.S. National Organic Standards Board (NOSB, purely an advisory committee) recommends that “potting mixtures devoid of or deficient in organic matter capable of supporting a natural and diverse soil ecology are prohibited. For this reason, hydroponic and aeroponic systems are prohibited.”2 But the US National Organic Program (NOP, the actual organic regulatory body), has reported that “there are 17 certified organic hydroponic operations at this time that are certified by USDA accredited certification agencies (ACAs).”2 Fortunately, regulations under the Canadian Organic Products Regulations are much more clear. But I digress, so back to the theme …

It’s fabulous that we’re seeing such an increase in interest in food production, gardens and horticulture technology within our schools. It’s a wonderful opportunity to teach students about the complexities of managing growing media, plant nutrition and the biota of the root zone. And any garden makes a fabulous classroom. After all, Geoff Lawton (permaculturist) famously said that “all the world’s problems can be solved in a garden.”

  • 1 (2015)
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Gary Jones is co-chair of Horticulture at Kwantlen Polytechnic University, Langley, B.C. He sits on several industry committees and welcomes comments at


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