I started growing microgreens without soil because I got tired of the mess. Potting mix on the kitchen counter, bits of it in the sink, and then a tray of soil to deal with every time I cut a batch. Switching to a bare tray solved all of that, and the greens turned out just as good.
Can you grow microgreens without soil? Yes. Soak the seeds, spread them in a single dense layer on a shallow tray or a damp growing mat, keep them covered in the dark for three or four days, then move them into bright light. Most varieties are ready to cut 7 to 14 days after sowing, and the seed itself carries enough food to get them there.
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Why Skip the Soil
A microgreen is harvested about a week after it sprouts, and in that first week the plant lives almost entirely off the seed. It barely touches the growing medium. Soil is there to hold moisture and nothing else, so a damp tray does the same job.
The practical difference shows up at harvest. Cut greens off a bare tray and they come up clean, with no grit to rinse out from between the leaves. There is also nothing to compost afterwards. You tip the root mat into the bin, rinse the tray, and it is ready for the next batch.
What You Need
A shallow growing tray without drainage holes, a second tray or a lid to cover it, a spray bottle, and seeds sold for sprouting or microgreens. A takeout container works perfectly well for a first try, which is what I used.
Buy seed labeled for microgreens rather than a regular garden packet. Garden seed is sometimes treated with fungicide, and you are eating these whole and raw. You also need far more seed per tray than you would for sowing a row, so the bigger bags work out cheaper.
Soaking the Seeds
Large seeds like sunflower and pea need a soak of 8 to 12 hours in cool water. It softens the shell and they come out of the gate much faster. Small seeds like broccoli, radish, kale and mustard sprout fine without soaking, and 20 minutes is plenty if you want to do it anyway.
Do not soak chia, flax or basil. Those seeds form a jelly coating in water that turns into a solid clump you cannot spread out. Sow them dry onto a damp surface and mist instead.
Spreading and the Dark Days
Drain the seeds and tip them into the tray, then push them around until they sit in one even layer. You want them close, almost touching, but not piled on top of each other. A stack of seeds two deep stays wet underneath and that is where mold starts.
Mist until everything is damp, then cover the tray so no light gets in. Some people weight the lid down with a book, which pushes the roots to grip harder and gives you straighter stems. Leave it in the dark for three or four days, lifting the cover once a day to mist and let some air through.
Around day three the tray fills with pale yellow shoots and a mat of white root hair. Those fine white hairs are normal and people mistake them for mold constantly. Root hairs sit only around the seed, they look fuzzy and even, and they vanish when you mist them. Mold spreads in patches, has a gray cast and smells sour.
Moving Into the Light
Take the cover off when the shoots have lifted about an inch (2.5 cm) and are pushing against it. They will look yellow and slightly alarming. Within a few hours in bright light they green up, and by the next morning you would not know they had ever been pale.
A bright windowsill is enough, though a south facing one is better. If the stems stretch tall and flop over, they are reaching for light and need a brighter spot or a grow light 6 to 8 inches (15 to 20 cm) above the tray. Turn the tray each day so they do not all lean one way.
Watering Without Soil
This is the part that catches people out. With no soil holding a reserve, the tray dries out faster, so mist twice a day and check it in between. At the same time there is no drainage, so standing water at the bottom will rot the roots. Damp, never puddled.
Once the root mat has formed you can switch to bottom watering. Pour a little water straight into the tray, let the mat drink it up for about ten minutes, then tip out whatever is left. Keeping water off the leaves at this stage makes a real difference to how long the tray stays clean.
How Long Each Variety Takes
Days are counted from sowing to harvest, growing indoors at normal room temperature. Radish is the one I recommend to anyone starting out, because it is up and ready before you have time to worry about it.
| Microgreen | Days to harvest | Soak first? |
|---|---|---|
| Radish | 5 to 7 | No |
| Mustard | 6 to 10 | No |
| Arugula | 7 to 10 | No |
| Broccoli | 8 to 12 | No |
| Kale | 8 to 12 | No |
| Cabbage | 8 to 12 | No |
| Pea shoots | 8 to 12 | Yes, 8 to 12 hours |
| Sunflower | 8 to 12 | Yes, 8 to 12 hours |
| Wheatgrass | 8 to 10 | Yes, 8 to 12 hours |
| Beet | 10 to 14 | Yes, 4 hours |
| Basil | 12 to 18 | No, forms a gel |
| Cilantro | 14 to 21 | Yes, 8 hours |
Harvesting
Cut when the first pair of true leaves starts to show between the two seed leaves. That is the peak for flavor, and waiting longer makes the stems tougher rather than giving you more.
Use scissors and cut just above the root mat, gathering a handful at a time. Harvest dry if you can, because wet greens go slimy in the fridge within a day or two. Cut dry, put them in a container lined with a paper towel, and they hold for about a week. Pea shoots are the exception and will give you a second cut if you leave the roots in place and keep misting. If you like those, green pea sprouts are worth growing on their own.
When Things Go Wrong
Mold almost always traces back to one of three things: seed sown too thickly, water sitting in the bottom of the tray, or no air moving. Thin the sowing next time, tip out the excess water, and lift the cover daily. A small fan in the room fixes stubborn cases.
Patchy germination usually means the seed did not stay evenly damp, often because one corner of the tray dried out. Stems that flop over are short of light. Seed hulls still stuck on the leaves after a week will come off if you mist firmly and brush a hand across the top.
FAQ
Can microgreens grow without soil?
Yes. The seed holds enough food for the whole growing period, so the greens only need moisture, air and light to reach harvest.
How long do soilless microgreens take to grow?
Most varieties are ready 7 to 14 days after sowing. Radish can be cut at 5 days, while cilantro and basil take up to three weeks.
Do microgreens need fertilizer when grown without soil?
No. They are harvested before the seed’s own food reserve runs out, so plain water is all they need.
Is the white fuzz on my microgreens mold or roots?
Root hairs sit close to the seed, look even and disappear when misted. Mold spreads in gray patches and smells sour.
Why are my microgreens tall and falling over?
They are not getting enough light. Move the tray to a brighter window or put a grow light 6 to 8 inches (15 to 20 cm) above them.
Can I reuse the tray for the next batch?
Yes. Lift out the root mat, wash the tray with hot soapy water and dry it before sowing again.
