The best growing medium for microgreens

Popular for their nutritional benefits, microgreens can be grown in the smallest living spaces with just water, a growing medium, and sunlight.

What are microgreens?

Microgreens are ordinary green vegetables harvested without their roots before maturing. They often contain higher levels of vitamins and nutrients than mature specimens of the same plant.

Growing microgreens typically doesn’t require nutrients, as harvesting early in the growing cycle means all necessary nutrients come from the seed and through photosynthesis.

Germinating seeds

Growing mediums for microgreens

A substrate should do three things:

  • provide a supply of water, air, and nutrients to roots
  • physically support the plant
  • allow maximum root growth

Soil

Soil is used because of the ease with which it can be acquired and used.

Most gardeners are comfortable using soil. It is naturally organic, offers predictable and consistent results, and retains moisture.

Most microgreens need only soil and water. Some brightly coloured plants, such as radish, may need added nutrients to flourish.

While soil is cheap to buy, be sure to go peat-free to protect the environment.

The downside of soil is the potential for mess, and inconvenient, bulky bags in small spaces. Soil is also prone to mould growth, which can lead to plant diseases and root rot.

Sterilised soil

Sterilised soil has been chemically- or temperature-treated to kill diseases, seeds, or pests. This minimises the chance of damping off and mould growth, making it better for growing seeds indoors. Small batches can be sterilised at home by baking in the oven at 180 degrees for 30 minutes.

Hemp mats

Hemp growing mats are natural and compostable. With a neutral pH, woven hemp fibre is water retentive and designed to distribute water evenly, promoting healthier germination. Mats provide a good mixture of air and water for young plants and don’t usually require nutrients.

The lack of mess and ease of cleaning once finished make for a great indoor growing medium. However, mats are flimsy and easy to rip once wet. This makes them hard to transfer or reuse. They can also be harder to source than soil or other alternatives.

Block of coco coir being rehydrated

Vermiculite

Vermiculite is a heat-expanded mineral mixed into soil or used as a growing medium. Providing excellent aeration, it minimises rot and damp for healthy root growth.

Some other key benefits:

  • holds moisture and nutrients well
  • mould-resistant
  • sterile
  • pH neutral
  • contains minerals such as magnesium and calcium.

While soil-less mediums are tidier, Vermiculite still has a loose structure which, after watering, can easily be displaced. This can result in compacting and loss of vital air pockets if moved or bumped.

Coco coir

Coco coir is made from coconut husks. It can be produced in different forms, including coco fibre, coco peat, and coco chips.

Coco coir products are naturally sterile, offering the benefits of sterilised soil without any processing required.

Both water retentive and porous, the moisture control it affords is perfect for healthy germination. Nutrients are absorbed better than in soil, allowing more exact application and providing a reliable, steady supply.

While coco peat can be messy, it creates and leaves less residue than soil.

Coir frequently comes in small, lightweight dehydrated bricks. This makes it easy to store in small spaces, when compared with ordinary soil.

It can also be reused multiple times, unlike hydroponic mats.

Soil vs hydroponics

Hydroponic projects are easier to set up, requiring only a tray, water, and seeds to start. However, more water is needed compared with soil as they dry out faster.

Mats are easier to dispose of or compost. They take up less space than soil but can only be used once. Every root and trace of harvested greens needs to be removed before reuse, which is almost impossible.

Soil, and substitutes like coco coir, can be consistently reused provided there are no harboured diseases or pests.

Larger seeds grow better in soil than in a hydroponic system. Most seeds will generate a higher yield in a good soil mix than when grown hydroponically.

Leaf of a blighted plant

Assessing the options for a growing project

Which growing medium you choose will depend on desired results.

If cleanliness is paramount, hydroponic mediums like hemp mats or coco fibre will be better.

For a reusable medium, opt for coir, vermiculite, or soil.

Soil, hemp mats and coco coir are compostable. However, some substrates are more environmentally friendly than others.

Coco coir is better than peat-based soil, which contributes to the destruction of non-renewable fragile ecosystems.

High-quality eco-friendly growing mediums

Coco coir utilises food waste by turning discarded coconut husks into a useful product.

At Coco & Coir we ensure the way we manufacture our coir-based products is eco-friendly from start to finish, creating the highest-quality soil substitute without depleting the planet’s resources.

If you’re growing in a small space and want to make use of the water-retentive, sterile properties offered by coco coir, check out our full range of products.

You can also take a look at our blog archive to learn more about using coco coir in your gardening projects.