It’s always one of the very first questions folks who’re interested in how I grow microgreens ask me. Do you reuse the soil?
The answer is No but Yes.
I don’t reuse the soil for growing more microgreens but a greenhouse full of shoots and microgreens, once harvested, includes a lot of amazing soil building material for my outdoor seasonal garden too. So yes, the microgreen growing soil is reused and has become an important part of my whole garden system.I first started making compost piles of harvested tray soil on the edge of the garden and once composted, I’d move it around to all my garden beds (which I still do) but somewhere along the way, as production increased, I realized that using the harvested tray soil was also an amazing way to make new beds right in place.
During the years when I was producing microgreens for grocery stores in Victoria, we were creating so much harvested tray soil that I had lots to give away to other Mayne Island gardeners. Folks would come load up the back of their pickup trucks or bring a tractor and wagon to load up or even throw some uncomposted trays onto a tarp in the back of their car!These days, I’m focussing on growing more manageable amounts of microgreens for our sweet island community here and I’m producing just what I need in soil amendments for this garden with a little bit to share with others, once in a while.It takes a couple months for the tray roots and stems to compost down in the winter cold and the summer warmth. In the spring tho’, the little plants that are left over, and some of the slower to germinate seeds want to continue to grow into larger plants and they often do. This results in delicious, juicy radish seed pods and big pea tendrils with purple and pink flowers and even mature sunflowers! Before the radish seed pods form, the radish flowers are a favourite of the swallowtail butterflies and it’s common to see over twenty of them at a time (I always lose count at around 20) flitting along over all the little radish flowers! Hummingbirds and all sorts of other pollinators love the radish flowers too. It all feels like a big bonus gift! This spring activity eventually dies down and things begin to compost as summer gets going.
Sometimes I use the harvested pea trays as a green manure crop over the fall/winter/spring time on beds that need a boost. I just lay down a patchwork of harvested tray remains and the greens begin to sprout again as the roots grow down into the soil and get to work fixing nitrogen. I do this around my apple trees and raspberry patch too. It really works!