The growing medium is what your microgreens root into. It holds moisture and air for the roots for one to three weeks — nothing more. Microgreens don’t need a rich soil, so the choice comes down to yield, cleanliness, cost and convenience.
Our recommendations
- Best all-round: a fine seed-starting or potting mix (peat or coir based).
- Cleanest loose medium: coco coir.
- Least mess, great for small crops: hemp or jute mats.
- Avoid: garden soil, heavy compost and mixes with large bark chunks.
Comparison table
| Medium | Yield | Mess | Mold risk | Cost per tray | Best for |
|---|---|---|---|---|---|
| Seed-starting / potting mix | Highest | Most | Medium | Low | All crops, especially peas and sunflower |
| Coco coir | High | Medium | Medium-low | Low | All crops; good soil alternative |
| Hemp mat | Medium-high | Very low | Low-medium | Medium | Brassicas, radish, wheatgrass |
| Jute mat | Medium | Very low | Medium | Medium | Brassicas, small seeds |
| Felt/synthetic pad | Medium | Very low | Medium | Low (reusable options vary) | Small seeds, quick crops |
| Paper towel | Low | Very low | High | Very low | Testing, tiny trays only |
“Mold risk” assumes correct watering and seed density. Any medium will mold if it’s soaking wet and has no airflow.
Potting mix and seed-starting mix
A fine, light mix is the traditional choice and gives the heaviest harvests, especially for big seeds. Look for:
- A fine texture, without large bark chunks or wood pieces, so small seeds can sit flat.
- A base of peat, coco coir or both, often with a little perlite or vermiculite.
- No added slow-release fertilizer or wetting agents if you can avoid them. Microgreens don’t need fertilizer, and strong fertilizer can burn young roots.
A 1–1.5 inch layer is enough. Downsides: it’s messy, it can carry fungus gnats if stored open, and you need somewhere to compost the spent trays.
Tip: if your mix is lumpy, rub it through a garden sieve or your fingers before filling trays. A smooth surface gives more even germination.
Coco coir
Coco coir is made from coconut husk fibre. It’s sold as compressed bricks that expand when soaked, so it’s easy to store and light to carry. It holds water well, drains freely, and is generally cleaner than potting mix.
How to use it: soak the brick in warm water according to the packaging (a common 650 g brick expands to several liters), break it up, and squeeze out excess water so it’s damp but not dripping. Fill trays 1–1.5 inches deep.
Coir is naturally low in nutrients, which is fine for microgreens. Choose a washed / buffered coir meant for horticulture; unwashed coir can contain salts.
Hemp mats
Hemp mats are thin felt-like pads made from hemp fibre. They’re cut to fit standard trays, so there’s almost no mess: wet the mat, sow, and grow.
- Pros: clean, fast to set up, good for brassicas, radish and wheatgrass, compostable.
- Cons: cost more per tray than loose media, dry out faster, and usually give somewhat lower yields for large crops like peas and sunflower.
Keep a thin layer of water in the bottom tray after blackout so the mat never dries out. See how to water microgreens.
Jute and other fibre mats
Jute mats behave like hemp mats but are usually thinner and hold less water. They work well for small, quick crops. Some brands shed fibres that can tangle in roots; this is harmless because you cut above the mat.
Synthetic and felt pads
Thin synthetic grow pads are used in some commercial and countertop systems. They’re tidy and can be good for small seeds, but check whether they are designed for food crops, and whether they are single-use or washable.
Paper towel
Paper towel can grow a handful of cress or a test tray of radish, but it dries out quickly and molds easily. Use it only for germination tests and tiny experiments.
What about garden soil or compost?
Avoid using them alone. Garden soil compacts in shallow trays, drains poorly, and often contains weed seeds, pests and disease organisms. Pure compost is often too rich and too wet. If you like, mix a small amount of well-finished compost into potting mix — but plain mix or coir is simpler and more consistent.
Which medium for which crop?
| Crop | Best medium |
|---|---|
| Pea shoots, sunflower | Potting mix or coco coir |
| Radish, broccoli, kale, cabbage, mustard | Any — mats work very well |
| Wheatgrass | Potting mix, coir or hemp mat |
| Basil, cilantro, amaranth | Fine seed-starting mix or coir (stays moist longer) |
| Beet, chard | Potting mix or coir, with light weight in blackout |
How deep should the medium be?
For loose media, 1 to 1.5 inches (2.5–4 cm) is ideal for most crops. Deeper medium holds too much water and wastes material; shallower medium dries out very fast. Mats are used as supplied, usually ¼ inch or less.
Frequently asked questions
Can I reuse growing medium for microgreens?
It’s best not to reuse it directly — old roots can harbor mold and gnat larvae. Compost it, and once fully broken down, it can be mixed into fresh potting mix.
Is coco coir better than soil for microgreens?
It’s cleaner and lighter, with similar results for most crops. Potting mix often gives slightly bigger harvests for peas and sunflower.
Do microgreens need fertilizer in the medium?
No. They grow on the energy stored in the seed and are harvested before they need extra nutrients.
What is the cheapest growing medium?
Coco coir bricks and bulk potting mix are the cheapest per tray. Mats cost more but save time and mess.
