How to Grow Microgreens

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How to grow microgreens is a short project with a simple method. You sow seed thickly in a shallow tray of moist potting soil, cover the tray until the seeds sprout, then move it into bright light and cut the young plants in one to three weeks. The Oregon State University Extension guide, the University of Illinois Extension, Penn State Extension and the University of Wisconsin-Extension Polk County page describe the same basic sequence, and their steps agree on almost every point. This guide draws on those four pages to set out a plan you can run on a windowsill.

Quick answer

Use a clean, shallow tray with drainage holes, filled with moist potting soil at least 1½ inches deep.
Sow the seed closely, press it in gently, and cover the tray until the seeds sprout, usually in about three to four days.
Once the seeds sprout, set the tray in a bright window or under a lamp, and water when the surface starts to dry.
Cut the greens with clean scissors just above the soil, then rinse them and use them right away.

Choose a shallow tray and good drainage

The container matters less than its depth and its drainage. The Oregon State guide lists a flat, clean growing container two to three inches deep, with drainage holes, among the things you need. The Illinois guide asks for something shallower and says a depth of one to two inches is ideal if you want to save on soil. The Wisconsin page takes the widest view. It says any shallow container will do, and it notes that restaurant carryout containers work well once you poke a drainage hole in the bottom.

Drainage is the part of the setup that the sources repeat. The Illinois guide describes a top tray with drain holes sitting over a second tray that catches the water. That arrangement allows bottom watering, and the guide says the catch tray can be the same kind of container, just without holes. The Oregon State guide’s warning about wet, cold soil appears in a later section of this guide.

For a wider view of trays, see our page on seed starter kits.

Fill the tray with plain potting soil

The sources ask for plain potting soil rather than anything special. The Oregon State guide says to moisten the potting soil before it goes into the container, then smooth the surface flat. The Penn State page notes that microgreens are commonly grown in standard greenhouse trays or seedling trays filled with soilless potting media. The Illinois guide asks you to level the soil, leave about a half inch of space between the soil and the lip of the container, and tamp the surface lightly with a flat object so the seeds sit on an even surface.

Sow the seed thickly and evenly

Seeding density is where the sources sound most alike. The Penn State guide says that when planting most microgreens, you should sow seeds thickly. The Oregon State guide tells you to sprinkle seeds closely together over the soil, press them in gently, and mist the soil until it is just damp. The Illinois guide says to broadcast the seed evenly across the surface and to pay attention to the edges.

Seed amounts depend on the seed. The Illinois guide gives rough amounts for a standard 10 by 20 inch flat. It separates large seeds, such as radishes, from the medium and small seeds used in mild and spicy brassica mixes. For those smaller seeds, it gives half a tablespoon to one tablespoon per flat. The Penn State guide does not give a single rate. It says that seeding rates depend on germination rates, seed size, soil and air temperatures, and light in the growing environment.

The Oregon State guide makes two practical points about seed. It says that seed from past growing seasons can work well, and that an older batch is worth testing with a small trial before you commit a full tray to it. It also suggests planting a few extra seeds so that enough sprout, and measuring a small amount, such as one teaspoon, to avoid wasting seed.

Cover the tray until the seeds sprout

All four pages agree that the tray needs a cover during germination. The Oregon State guide says to cover the container to block light and hold in moisture. The Illinois guide says that a plastic lid or covering increases humidity and helps germination. It also accepts paper towels, cloth, or a second tray stacked on top of the seed in place of a lid. Once the microgreens sprout, the Illinois guide says the cover is no longer needed.

Timing is the detail to watch. The Oregon State guide puts sprouting at around three to four days. Once the seeds have sprouted, it says to remove the cover and place the container in a bright window or under a lamp. The Wisconsin page gives the reason in one line: keep the seed moist with the cover only until it germinates, then remove the cover so heat and humidity do not build up.

Give bright light and turn the tray

Light decides whether the young plants grow straight and sturdy. The Oregon State guide says that a lamp can be as close as three inches above the plants and should run during normal waking hours, which it calls ideal at about 15 hours a day. It also says that a window or a table lamp is the best setup for year-round planting indoors. For a wider look at lamps for starting seeds, see our guide to grow light options for seedlings.

Dim light causes trouble. The Oregon State guide says that dim light makes microgreens lean toward the light, producing plants that are leggy. The Illinois guide asks you to place the tray in a sunny window and rotate it, because seedlings lean toward the light and turning gives all sides an even share of it. The Oregon State guide also says to rotate the container so the greens grow straight. The Wisconsin page also says to put the tray in a sunny window and/or under lights.The sources describe the same habit from different sides: stems stretch toward the light, so the tray has to be turned.

Water gently and keep the surface damp

Watering is gentle in every source. The Oregon State guide says to mist the soil until it is just damp. The Wisconsin page says to mist or bottom water carefully so the seeds are not dislodged, and to water when the surface starts to dry. The Illinois guide describes bottom watering, putting water into the bottom tray, as the best way to keep the microgreens dry.

Keep the temperature moderate

The Penn State guide gives the ideal soil temperature for germinating microgreens as 60 to 75°F, with air temperatures between 60 and 70°F. Those figures are ideal ranges, so they set a target rather than a strict requirement. The Illinois guide says a germination heat mat is optional, because a sunny window at room temperature should do the trick too.

Cold, wet conditions are the main hazard. The Oregon State guide warns that microgreen seeds and seedlings can rot or get moldy if the soil is too wet and cold. The Penn State guide notes that microgreens will grow under less than ideal conditions, because they only need a short growing period. Those two statements balance each other: the crop is quick, but soil that stays cold and soggy is the thing to avoid.

Pick mild or spicy types for the first tray

The Oregon State guide sorts common microgreens by flavor. Its mild group includes broccoli, cabbage, cilantro, chard, kale, peas and sunflower. Its spicy group includes arugula, mustard greens and radish. The guide adds a note that cilantro might take longer than the others, so a cilantro tray may need a few extra days before cutting.

The Penn State guide lists a longer set of common types, including amaranth, dill, kale and parsley. That overlap shows that several plants grown for their leaves also appear as microgreens. If you already grow amaranth or dill in a garden bed, a tray of the same plant is a small step to try.

Harvest with clean scissors and use the greens quickly

Harvest timing differs by source, and the differences matter. The Penn State guide says production can take as little as seven days and up to 21 days from seeding to harvest, depending on the environment and the type. The Illinois guide says one to three weeks, depending on whether you want the cotyledon stage or the first true leaf stage. The Wisconsin page says most microgreens are harvested within 14 days of planting, when they are three to four inches tall.

For cutting, the Oregon State guide says to use clean scissors and cut above the soil. The Illinois guide asks for a sharp knife or scissors and a cut about a quarter inch to half an inch above the soil line. The Wisconsin page says to harvest after the first set of true leaves has developed. Once cut, the Oregon State guide says the best plan is to harvest, rinse and use the greens right away.

Storage is short. The Oregon State guide says to wrap the greens in a paper towel, place them in a plastic bag, and keep them in the refrigerator for one to two days. When a tray is finished, the Illinois guide says you can compost the remaining stems and soil. The Wisconsin page says to empty the container and start another crop.

Troubleshoot leggy plants and soggy trays

Two problems appear in more than one guide. The first is leggy growth, which the Oregon State guide ties to dim light. The second is rot and mold, which the same guide ties to soil that is too wet and cold. The guides point to the same two levers when a tray goes wrong: light and water. Check the window or lamp first, then check how wet the soil stays between waterings.

Plan a steady supply

A single tray gives you a single harvest. The Wisconsin page recommends planting some every few days to have a steady supply. The Illinois guide describes the cycle that makes that possible: harvest the tray, compost what is left, and sow again. The Oregon State guide describes year-round planting indoors, as long as the tray has a window or table lamp. The Penn State guide says most of the labor comes at planting and harvest.

How we chose

We chose the pages for this guide by searching for university extension guides on growing microgreens and then opening each candidate with curl. Four pages returned HTTP 200 and contained growing instructions: the Oregon State University Extension guide, the University of Illinois Extension PDF, the Penn State Extension article, and the University of Wisconsin-Extension page for Polk County. We kept the steps that more than one page states, and we flagged the places where the pages disagree, such as container depth. We left out seed-company and retail pages, since they describe products rather than the method.

What we could not verify

The four pages are short extension guides, and none of them gives a complete table of yields, costs or shelf life for every crop. We did not check any seed product, tray or lamp, and this guide does not recommend one.

What the sources do not say

The sources do not say which microgreen type will be ready first in your home, because timing depends on the environment and the crop. The Penn State guide gives a range of seven to 21 days, the Illinois guide gives one to three weeks, and the Wisconsin page gives about 14 days for most types. Those are ranges, not promises. The Penn State and Wisconsin pages also make claims about nutrient content, but they do not show the data behind those claims, so this guide does not repeat them.

Frequently asked questions

How long does it take to grow microgreens?

The Penn State guide gives a range of seven to 21 days from seeding to harvest, depending on the environment and the type. The Illinois guide says one to three weeks. The Wisconsin page says most types are harvested within 14 days of planting.

Do microgreens need a grow light?

The Oregon State guide says a window or a table lamp is the best setup for year-round planting indoors. It also describes a lamp that can sit as close as three inches above the plants. The pages do not say that a special grow light is required.

Which tray works for microgreens?

Any shallow container will do, according to the Wisconsin page, and the Illinois guide asks for drain holes. The Oregon State guide describes a container two to three inches deep, while the Illinois guide suggests one to two inches if you want to save on soil.

Why do microgreens grow leggy?

The Oregon State guide says dim light makes microgreens lean toward the light and produces leggy plants. The Illinois guide recommends placing the tray in a sunny window and rotating it, because seedlings lean toward the light.

How long can harvested microgreens be stored?

The Oregon State guide says to wrap the greens in a paper towel, place them in a plastic bag, and store them in the refrigerator for one to two days. It also advises harvesting, rinsing and using the greens right away.

Sources

https://extension.oregonstate.edu/node/236276 (opened 2026-10-23)
https://extension.illinois.edu/sites/default/files/growing_microgreens_1.pdf (opened 2026-10-23)
https://extension.psu.edu/growing-microgreens (opened 2026-10-23)
https://polk.extension.wisc.edu/2016/01/29/growing-microgreens-now/microgreens/ (opened 2026-10-23)