You have seeds, planting trays, and light. Now what? What are you missing? The one thing that will make or break your new little micro-farm: the planting medium!

First, an explanation:  dirt, soil, and growing medium are not the same thing.

Dirt is what you get on your hands when you are having fun in the garden. Soil is made up of stuff that has been decomposing since the earth was created. The growing medium, or grow media, is the stuff that plants grow in.

Seeds were designed to grow in soil and to develop the most nutritious microgreens, it is important to grow in as natural an environment as possible. Although there are those that advocate growing in soil-less materials such as hydroponics, to get the most nutrient-dense microgreens, the seeds need a healthy, balanced grow media

An important tip: avoid garden soil, topsoil, planting soil, and potting soil like the plague!  ‘Soil’ on its own is never for containers because it is dense and heavy. It collects too much water and pushes out the air from around the roots causing rot and mold. Soil can be a minor part of a grow medium, but must not be more than 10%.

The grow media for microgreens has three functions: 1. Support the plants as they grow, and 2. Supply them with nutrients, and 3. Control the air and water in the container. The best grow media for your microgreens is one that is light and ‘fluffy’, that holds water but also holds air in the medium.

Here are 3 options for excellent microgreen grow media.

Potting mix

For both the beginner and the experienced microgreen grower, the easiest way to get a good growing media for microgreens is to purchase a good quality potting mix. Note that there is a difference between potting soil and potting mix. Check the ingredients- it should include ingredients such as perlite, vermiculite, coconut coir, or sphagnum peat moss. The purpose for these ingredients is to lighten the media, allowing air to circulate around the roots, and letting the tiny roots easily embed themselves into the nutrient-filled layer. Potting mix is easy to find at many big-box stores, nurseries, and even some supermarkets. It comes in an easy-to-use bag and is easy to store and use. It contains all the nutrients that the seeds need to grow even past the microgreen stage.

Coco coir

Coco coir is an environmentally conscious product that is ideal for growing microgreens. Coir is the outer part of the coconut that used to be put in the waste. Coir has the benefit of being full of nutrients, having excellent drainage ability, and allowing the perfect amount of air retention for the roots. It is clean to work with, and because it has natural anti-fungal properties, it can help minimize pathogens and some pests.

Coco coir is normally purchased in compressed blocks that require rehydration. Rehydrating can be a tedious, messy affair. Coir can also be purchased pre-hydrated in ready-to-use bags, but this normally costs quite a bit more than either block coir or potting mix. Be aware that some coir products are prepared using salt water which makes the coir too salty to use in containers. Be sure you buy coir from a reputable source.

Make your own grow media

There are many options for making your own grow media from mixtures of soil, compost, coir, peat, perlite, vermiculite, and sand. It can be difficult to get the mix a ‘just right’ combination of nutrients, density, pH, and with the right balance between moisture retention and aeration, but can be a cost-effective option for those that are growing many trays of microgreens each week.  For those that have space, time, and interest, making your own potting mix can bring you back to your childhood when you added ‘a little of this and a little of that’ in your play. Find instructions online for potting mixes and how to choose the right ingredients

Whichever grow media you choose, remember that you only use the media one time in a tray. Never reuse grow media for microgreens unless it has been properly composted in between. This prevents a build-up of pathogens in the soil that, because we harvest so close to the soil, has the potential to transfer to our food. After harvesting, add the leftover to a compost bin, or simply fill a flower pot with it and mix it up. A third method of getting rid of the mix is to talk to a gardener in the area and ask to dump your trays in their garden area. Free compost for them and an ecologically sound solution for you!

Questions? Ask them below…