Do you grow Medium?

15 May, 2024

In our ongoing pursuit of sustainability, we are delving deeper into the very roots of our growth process. This pivotal stage in the growing cycle holds immense potential for cost savings. Enhanced germination minimizes seed waste and accelerates plant growth, reducing overall growth time and, consequently, costs. This path is not just worth exploring, but it’s a journey we invite you to join us on as we strive for sustainable and efficient cultivation methods.

We have rotated through the industry standards and compared Rockwool and peat plugs in the past. Both have served us well, and although we have noted some differences in the early days of growth, the plants’ growth schedule, size, and health are nearly identical. Depending on your growing system, Rockwool and peat plugs have unique pros and cons. Peat breaks down through the growth cycle, creating additional debris to manage, and Rockwool should be physically torn apart for proper disposal. Rockwool is considered “landfill safe” but is not biodegradable. Both problems are handled with a bit of know-how and care.

If you grow enough, you realize that the cost of both Rockwool and peat plugs adds up. They are not consumed or reusable, and their role in the growing process ends within days of planting. However, the recent introduction of reusable substrates could change the cost dynamics of cultivation. It’s an expense that is worth exploring further.

We have been experimenting with a sterile gel made from agar for several months. Agar is standard in research, and most people have had the opportunity to use or taste it, even if they didn’t know it. This jelly-like substance is a mix of carbohydrates extracted from red algae, a type of seaweed and water. In cooking, agar-agar is used as a vegetarian alternative to gelatin in various dishes, including puddings, mousses, jellies, ice cream, gummy candies, and cheesecake. It is an essential ingredient in the Japanese dessert anmitsu, which calls for kanten jelly, a mixture of agar-agar, water, and sugar. It took some time to dial our agar recipe and we had a few failures before we began to see the opportunity agar gel presented. We monitored germination, plant growth rate, root health, and the impact on our hydroponic system until we were confident in its effectiveness.

We were recently provided several grow medium substitutes for testing, and we felt this was the perfect opportunity to retest our original grow medium trials, this time including the reusable substrate with agar to provide temporary adhesion and moisture.

Grow Medium Trial Parameters:

Grow Mediums:

  • Rockwool
  • Peat plugs
  • Silicone with agar gel


  • Little Gem lettuce seeds


  • No nutrients are added for germination.
  • No light, artificial or natural, used for germination
  • All seeds are placed together within the same seed tray with a humidity dome.


  • Day 3: All seeds germinated across all grow mediums.
  • Day 7: All seeds have grown cotyledons (little leaves) with no noticeable stem, shape, size, colour, or differences above the growing medium.
  • Day 7: When exploring changes to the underside of the growing medium, roots were well-established and viewable in the reusable growing medium.
  • Day 10: Seedlings growing in the Rockwool and peat plugs look healthy, with signs of the first “true leaves.” No roots were evident with the Rockwool, but roots were evident with the peat plug and reusable medium.
  • Day 10: Seedlings within the reusable substrate displayed more advanced leaf growth, richer colour, and a thicker stem. The stem’s length was shorter relative to the Rockwool and peat plug.
  • Day 10: Due to the length of the roots, the reusable substrate has been moved to the aeroponic seedling chamber.

We will continue to monitor the growth and provide an update in the following weeks. However, the reusable substrate has performed as well, if not better than our go-to grow mediums. Why is this exciting? If we have the opportunity to transition to a reusable substrate without sacrificing plant growth, this is environmentally and financially beneficial!

Stay tuned! More updates to come.

Grow the good!