Substrate-Based Methods for Microgreens

Substrate-based methods offer a robust introduction to microgreen production. The roots grow in a loose growing medium or a thin fibre mat, while a perforated tray sits inside a solid bottom tray. This combination provides even moisture and clean bottom watering.

Hemp mats and jute fleece

Natural-fibre mats keep seeds in place and reduce the amount of substrate particles on the harvested crop. Hemp and jute can be cut to size and are often compostable. It is essential to use food-safe, uncontaminated products, select water retention suited to the variety and ensure full contact between seeds and mat. Very large seeds such as peas often require a thicker mat or additional covering.

Coconut coir

Coconut coir provides a good balance of air-filled pores and water-holding capacity. Compressed blocks are hydrated evenly before sowing. Depending on their origin, they may contain soluble salts; the manufacturer's instructions, initial EC and rinsing where necessary are therefore more important than a one-size-fits-all recipe. Fine coir particles must not enter a recirculating system without filtration, as they can place a strain on pipes and pumps.

Cellulose and organic cotton fibre

Thin cellulose mats are clean, lightweight and easy to automate. Their low buffering capacity, however, calls for more frequent moisture checks. Sustainability and disposal depend on the material, binding agents, origin and whether the product is compostable.

Practical workflow

1. Select clean trays and a food-safe growing medium.
2. Moisten the medium evenly until it feels like a wrung-out sponge.
3. Weigh the seeds according to the variety and distribute them evenly.
4. Monitor the germination phase and ventilate the cover regularly.
5. Once the seedlings emerge, preferably water from below and drain off any remaining water.
6. Harvest above the growing medium with clean tools.

Strengths and limitations

Technical sources

• University of Maryland Extension: Growing Microgreens Indoors
• Penn State Extension: Step-by-Step Guide