Up until recently, we used coconut coir to grow our microgreens. In a previous post, I compared peat moss to coconut coir. I concluded that coconut coir was the more sustainable option for us. It has, however, always intrigued us to use a reusable grow medium.
our motivation
sustainability
From a sustainability point of view, it’s obvious that a reusable medium has several advantages:
- We don’t need a medium like coconut coir produced on the other side of the world, packaged and transported to us.
- After harvesting, we’re not left with a medium that we can no longer reuse and can only compost.
organic certification
We also had another reason to investigate a reusable medium further. From 01/01/2022, microgreens could become certified organic in the EU under strict conditions.
In ANNEXE II of Regulation (EU) 2018/848, the following is specified:
“1.3. By way of derogation from point 1.1, the following shall be allowed:
(a) the production of sprouted seeds, which include sprouts, shoots and cress, solely living on the nutritional reserves available in the seeds, by moistening them in clear water, provided that the seeds are organic. The use of growing medium shall be prohibited, except the use of an inert medium intended solely to keep the seeds moist when the components of that inert medium are authorised in compliance with Article 24;”
In short, for microgreens to be certified organic in the EU, they need to grow solely with the nutrition available in the seeds. Microgreens can not get any nutrition anywhere else, not even from the growing medium. Coconut coir provides (limited) nutrients to the microgreens, so this is not allowed.
stainless steel meshes
Long before we knew about the EU regulations for organic microgreens, we had already purchased a food-grade stainless steel mesh to experiment with. We cut it to size ourselves.
We liked the idea of stainless steel meshes since stainless steel can be fully recycled back into stainless steel. It matched our values perfectly.
At first, we were enthusiastic to see that we could grow microgreens like this, but stainless steel had some downsides:
- Cutting the meshes took time.
- We couldn’t get the meshes to become completely flat. This made our sowing slightly uneven.
- The metal borders were very sharp and a hazard.
- Cleaning the metal mesh was very difficult. The material is sharp and inflexible. On top of that, the wires of the mesh would unravel.
We would have been able to deal with these annoyances on a small scale, but we needed to keep in mind that we wanted to find a scalable solution. There was no way that we would be able to clean hundreds of these meshes on a weekly basis without losing our minds.
We had some ideas on how to improve the mesh, but at our current scale, we couldn’t find a provider who could create the product we had in mind at a price that we were ok with paying.
plastic meshes
After letting go of the idea of stainless steel meshes, we started investigating plastic meshes. Based on our experience with the stainless steel meshes, these were some of our requirements:
- A flat mesh so that we can sow evenly.
- A flexible mesh so that we can easily clean it after use.
- A mesh that does not unravel when cleaned with a brush.
- A food-safe material.
- A material that is water-resistant and can withstand the light of full-spectrum grow lights.
We experimented with different materials and mesh sizes (the size of the hole in the mesh) until we found a combination that matched all of our requirements.
These are the meshes we are now also selling in our webshop:
- Reusable Microgreen Mesh Grow Medium – Fine Size – 5 pack
- Reusable Microgreen Mesh Grow Medium – Coarse Size – 5 pack
sizes
We decided to use two sizes of meshes.
- We use the fine size for our brassica seeds (broccoli, kohlrabi, red cabbage, and mizuna) and rocket.
- We use the coarse size for larger seeds like radish, peas, and sunflower. Lately, we’ve been growing our peas directly in our growing trays, though.
ease of use
As mentioned before, it was important to us to find a solution that would allow us to scale up. We were worried about cleaning the meshes, but as it turns out, the meshes changed many steps in our process.
sowing
Sowing has become a lot smoother since we eliminated coconut coir.
We no longer need to:
- soak and prepare the coconut coir
- add the coconut coir to each tray
- flatten the coconut coir
Instead, this is our new sowing process:
- Place the mesh in the growing tray.
- Mist the mesh with water. This makes the mesh “stick” to the tray, so it becomes completely flat. It also allows the seeds to stick to the mesh.
- We evenly distribute our seeds on the mesh, as we would with any medium.
- Lastly, we mist the seeds. You will notice that the cells of the meshes hold the water.
growing
A big advantage of the meshes is that we have a lot of control over the water that our microgreens get. We’ve barely had mould issues since switching to the Garland trays (they have excellent drainage), but the combination with the meshes makes it even rarer.
harvesting
Harvesting with the meshes is a breeze:
- We take the mesh with the microgreens out of the tray. Our microgreens have never been so easily accessible to harvest.
- Our harvest is super clean. No coconut coir can get mixed with our harvest.
- The only waste we have after a harvest is the roots, which are perfectly compostable.
cleaning
Our trays are now much cleaner after harvesting compared to when we used coconut coir. All we need to do is hose them down and disinfect them.
The only aspect of our process that has become slightly less efficient is cleaning the meshes. There are many techniques to clean the meshes. We remove all matter from the meshes right after harvesting.
This is the method that works best for us:
- Once we harvest our microgreens, we use a plastic scraper (like to remove ice from a car windshield) to wipe off the roots from both sides of the mesh.
- We then rinse the mesh with water while rubbing away the matter that’s still attached to the mesh.
- Lastly, we disinfect the meshes with H2O2 and hang them to dry.
productivity & growing technique
It took us months to finetune our growing technique with coconut coir.
Ever since we started using the meshes, we’ve had to experiment again to find the method that works best for us.
It should be no surprise that our average harvest weight initially dropped for every type of microgreen we grow. The coconut coir boosted our microgreens, and with the meshes, our microgreens are growing solely with the nutrients available in the seeds. We also don’t use any other type of added nutrient, as this is also not allowed in organic farming for microgreens in the EU.
Our experiments have paid off, though. As our average harvest weight keeps going up, we are almost back at the level of our coconut growing days.
To our surprise, some microgreen types preferred the meshes over the coconut coir. Rocket, Red Mizuna and Purple Kohlrabi have never looked better.
cost-efficient
Last but not least, it’s clear that the meshes are interesting from a financial point of view. Before, we spent money on grow medium for every tray we grew. Now, we invested one time in a grow medium that we can use over and over again.
