Small Space Greens

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Can you grow microgreens on a windowsill?

Several extensions say yes, with a bright window. A lamp is the backup when stems lean hard toward the glass.

By Ryan Moalemi. Updated November 9, 2026.

Yes. A windowsill can grow microgreens if the glass is bright and you treat light as the limiting factor, not as a guarantee. Iowa State University Extension says microgreens are feasible indoors in an Iowa winter with a sunny window. Francesco Di Gioia at Penn State Extension writes that sunlight behind a window, on a balcony, or on a small porch is generally enough, and that a south-facing window usually receives more than a north-facing one. Utah State University Extension says a southern window can work, and it reminds readers that a Utah winter day can be as short as about 8 hours of sun. University of Maryland Extension is the cautious version: a sunny window may suffice, and microgreens generally grow better under lights.

Those sentences are the whole answer. The rest of this page is how to use a sill without pretending every window is a greenhouse, and when the same universities would rather you add a lamp. Nothing here is from a sill grown for this site.

Photo coming soon. A shallow tray of microgreens on a south-facing apartment windowsill, stems upright rather than leaning into the glass.
Photo coming soon. Planned photo: a tray on a south-facing sill, stems upright, no brand labels.

What "enough light" means for this crop

Microgreens are harvested small, so they do not have to live for months on weak light the way a tomato transplant does. Penn State Extension calls them a low-light crop, with a daily light integral below 20 mol per square meter per day in that article's terms, and says they can finish under less than ideal conditions because the production window is only about 7 to 21 days. That is permission to try the window. It is not permission to ignore pale, tangled stems.

If you do add light, the hour counts already published are straightforward. Maryland suggests about 16 hours total from sun plus lamp, with fixtures typically 6 to 12 inches above the leaves. Utah State's guideline is 18 hours on and 6 hours off. A timer is the tool Maryland mentions so the day length does not depend on you remembering a switch. LED lamps, in that same Maryland note, use less electricity than fluorescent lamps for a comparable amount of light. The article does not rank brand names, and this page will not either.

There is a different Cornell warning you should not mix up with this crop. Steve Reiners, writing for Cornell about vegetable transplants, says even a sunny south window does not provide enough light in quantity or quality to raise sturdy transplants, and he describes fluorescent lamps kept about 4 inches above the plants for 16 to 18 hours. That advice is about plants you will grow on for weeks and then set outdoors. A microgreen is cut at about 1.5 to 3 inches. Use Reiners when you are starting tomatoes and peppers, which is the seed-starting guide. Use the microgreen authors when the crop is the tray itself.

Which crops are fair to a weak window

Maryland says lettuce, arugula, mustards, and Asian greens grow acceptably in less-than-ideal light. Radish is a brassica relative of those mustards and is a reasonable first sill crop for flavor and speed. The comparison with pea, which wants a soak and a heavier sowing, is in pea versus radish. Illinois Extension's faster list (arugula, kale, radish, broccoli, mustard, and similar greens) overlaps the crops most people try first on a sill. Its slower list (amaranth, beet, cilantro, basil, pea, sunflower, and others) is a weaker match for a dark winter window, because the plants sit longer before you can cut them.

Basil and cilantro are the long clocks in the Utah State table: basil about 12 to 16 days to harvest after a 4 to 7 day cover, cilantro about 21 to 28 days after a 7 to 14 day cover. A long cover on a cold sill is a mold risk. If the only light you have is a north window in December, pick a short brassica and plan a lamp, rather than a three-week cilantro tray in the shade.

How to place the tray

Put the tray against the glass only if the leaves do not touch a freezing pane. Di Gioia says shoots lean toward the light when the level is limited. That lean is your meter. Rotate the tray every day so the lean does not become a permanent bend. A south or west sill in the northern hemisphere is the first place to try. An east sill can work for a short crop. A north sill is the one to supplement.

A January pane can be colder than the room. Penn State gives germination soil of about 60 to 75°F. Maryland says about 70 to 75°F, and Utah State about 74°F. If seed sits with no movement, move germination back into the room, covered, then return the tray to the glass. Do not park a covered wet tray on a radiator.

Water on a sill wants the same bottom-up habit as anywhere else. Mississippi State says bottom watering is effective on a kitchen windowsill. A reservoir tray protects the paint and the wood. Pull the growing tray out once the mix is moist so you are not steeping roots all afternoon. The steps are in bottom watering. A small fan matters more on a still winter sill than in a breezy room, because the canopy stays wet longer. Maryland, Utah State, and Di Gioia all mention moving air. Crack the cover during germination so humidity can leave.

A simple two-week trial

  1. Sow one small tray of arugula or radish, not a mix. Use the gram rate scaled in the calculator for the container you actually own. A full 10 by 20 inch flat may not fit the sill. A 5 by 5 or a 10 by 10 often will.
  2. Germinate covered, off the coldest part of the glass if the pane sweats or feels icy. Uncover when the seed is up.
  3. Give the tray the brightest sill you have. Rotate it daily. Note whether stems lean and whether color is deep or pale.
  4. If, after a few days in the light, the stems are long, pale, and falling over while a second tray under a lamp nearby is shorter and darker, the window is not enough for that week. Add hours with a lamp rather than sowing a third identical tray.
  5. Cut at about 2 to 3 inches, or when true leaves open, which is the harvest stage Maryland and Iowa State describe. A University of Vermont handout says 1 to 3 inches. You are judging the plant, not hitting a single height from one author.

If you add a lamp, use Maryland's roughly 6 to 12 inches and 16 hours, or Utah State's 18 hours. Watch for heat on the leaves. This page does not invent a wattage.

When to leave the sill

Keep the sill if plants color up and stand. Add a lamp if they lean or stall. A milder season can move the project to a balcony, which is a different crop stage. Do not set a covered germination tray outside in a freeze.

Also leave the sill if you are starting transplants for that balcony. Reiners's Cornell column is the one to follow then, because those plants need weeks of strong light, not a week and a half. The microgreen tray can stay as the crop you eat while the transplants grow somewhere brighter.

FAQ

Is a north-facing window enough?

It is the weakest default. Di Gioia notes that a south window usually gets more sun than a north window, and that shoots lean when light is limited. You can still germinate on a north sill and then add a lamp. Do not expect the same color as a south sill in winter.

How many hours of window light do microgreens need?

The published hour targets are for light in general, not for sun only. Maryland suggests about 16 hours. Utah State uses 18 hours on and 6 off when it is running lamps, and it notes winter sun can be about 8 hours in Utah. If the window cannot approach those hours, a timer and a lamp fill the gap.

Will any microgreen work on a sill?

Maryland specifically names lettuce, arugula, mustards, and Asian greens as tolerant of weaker light. Short brassica crops fit a sill better than crops with a long cover, such as the cilantro schedule in the Utah State table. Pea can be grown at a window, and it still wants its soak and weight.

Why do transplant guides say a window is not enough?

They are talking about plants that must stay stocky for weeks. Steve Reiners at Cornell says a south window is not enough for healthy transplants and recommends lights close to the leaves. Microgreen guides allow a window because the harvest is early. Use the guide that matches the crop you are actually growing.

Sources

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