Growing microgreens without soil is cleaner, quicker to set up and easier to fit into a kitchen. There’s no bag of potting mix to store, no soil on the counter, and less risk of fungus gnats. Yields can be a little lower than in soil for some crops, but for radish, brassicas and wheatgrass the difference is small.
Why grow without soil?
| Advantage | Trade-off |
|---|---|
| Very little mess | Mats and kits cost more per tray than loose soil |
| No fungus gnats from bagged soil | The surface dries out faster — needs closer attention |
| Faster setup and clean-up | Large-seeded crops (peas, sunflower) usually yield less |
| Clean harvest with no soil on stems | Slow crops may need a little nutrient solution |
Method 1: Hemp or jute grow mats
This is the most popular soil-free method.
- Place a growing tray with drainage holes inside a solid tray.
- Lay a hemp or jute mat in the growing tray and soak it thoroughly. Pour off any excess so the mat is saturated but not floating.
- Sprinkle seed evenly over the mat at the usual rate — see the seed density chart.
- Mist well and cover for the blackout period, misting daily.
- After uncovering, keep a thin layer of water — around ¼ inch (5 mm) — in the solid tray so the mat wicks it up. Refresh it daily so it doesn’t go stale.
- Harvest by cutting above the mat. Compost the mat afterwards.
Best crops: radish, broccoli, kale, cabbage, kohlrabi, mustard, arugula, wheatgrass.
Method 2: Mesh tray over water
Some trays have a fine stainless-steel or plastic mesh insert that sits just above a reservoir of water. The seeds sit on the mesh, and the roots grow down through it into the water.
- Fill the reservoir until the water just touches the underside of the mesh.
- Spread seed thinly on the mesh. Pre-soaked large seeds work well here.
- Cover, and mist the seeds twice a day until roots reach the water.
- Once roots are in the water, lower the water level slightly so the upper roots get air, and change the water every 1–2 days.
Best crops: pea shoots, wheatgrass, broccoli, radish, sunflower (with care). Mesh trays are reusable, which saves money over time — clean them thoroughly between crops.
Method 3: Jar or sprouter (for sprouts, not microgreens)
A jar with a mesh lid grows sprouts, not microgreens: the seeds sit in the jar and are rinsed several times a day, and you eat the whole sprout. It’s the simplest soil-free method of all, but it’s a different product with different food-safety advice. See microgreens vs sprouts.
Method 4: Countertop kits
Countertop microgreen kits usually combine a small tray, a pre-cut pad, and sometimes a built-in light and reservoir. They’re convenient and tidy, though refill pads can be expensive per harvest. Check that replacement pads are easy to buy, or that you can cut a generic hemp mat to fit.
Do soil-free microgreens need fertilizer?
For most crops harvested in 7–14 days, no. The seed contains enough stored energy.
For slower crops grown on mats — basil, cilantro, amaranth, beet — some growers add a very dilute hydroponic nutrient solution to the water after the first week, at a fraction of the label’s normal strength. If you try this, use a product designed for hydroponic food crops and follow the label. Plain water is fine for most home growing.
Keeping a soil-free tray healthy
- Never let the mat dry out. Mats hold less water than soil; check twice a day near harvest.
- Don’t drown it either. The mat should be wet, not floating in standing water.
- Change the water regularly in reservoirs and bottom trays to keep it fresh.
- Run a small fan for gentle airflow.
- Sow at the right density. Over-sowing is just as much of a problem on mats as on soil.
Troubleshooting
| Problem | Cause | Fix |
|---|---|---|
| Seeds drying out and not germinating | Mat surface dried during germination | Keep covered; mist twice a day |
| Roots lifting seeds off the mat | Poor contact; mat too dry | Press seeds gently; keep the mat wetter in the first days |
| Slimy roots or sour smell | Stale water or waterlogged mat | Change water daily; drain excess |
| Yellowing slow crops | Seed energy used up | Harvest sooner; consider very dilute nutrients |
| Mold patches | Too dense, too wet, no airflow | Thinner sowing, fan, less water |
Frequently asked questions
Do microgreens grow as well without soil?
Fast crops like radish and broccoli grow nearly as well. Peas and sunflower usually give heavier harvests in soil or coco coir.
Can I reuse hemp mats?
They’re designed for single use. Compost them after harvest.
Is coco coir “soil-free”?
Technically yes — coco coir contains no soil — but it behaves like a loose medium. Compare options in our growing medium guide.
Can I grow microgreens in just water?
On a mesh tray, yes. Seeds sitting directly in a dish of standing water usually rot.
