How Much Light Do Indoor Herbs Actually Need?

October 25, 2026

If you change one thing about how you grow herbs indoors, change how you think about light. A room can feel bright to you and still be far too dim for a plant. Most herbs that stretch, flop or quietly stop growing are not being overwatered or underfed. They are short on light.

The short answer

University extension guidance lands in a consistent range:

Penn State Extension and Michigan State University Extension both point to at least six hours of direct sun a day for most herbs.
Iowa State University Extension notes that most herbs grown indoors do best with around eight hours of direct light, with some tolerating as little as six.
Under artificial light alone, herbs need longer days. Iowa State suggests 12 to 16 hours on a timer, and University of Maryland Extension suggests 14 to 16 hours for winter supplemental lighting.

Direct light means sun actually landing on the leaves, not just a bright room.

Bright versus low light environments

Bright: direct sun on the leaves

A sunny windowsill where the plant sits in direct sun for six hours or more. Most culinary herbs can grow here without help, especially from late spring through summer.

Medium: bright but mostly indirect

A spot near a window that gets a few hours of direct sun, or bright light that is filtered by sheer curtains or nearby buildings. The more forgiving herbs can manage here, and most herbs benefit from a few extra hours under a grow light.

Low: no direct sun

A north facing window, a spot several feet back from the glass, or a kitchen counter away from windows. Herbs will not thrive here on daylight alone. Plan on a grow light as the main source.

Understanding window direction

In the Northern Hemisphere:

South facing windows get the most direct sun through the day and are the best natural option.
West facing windows get strong afternoon sun and can work well.
East facing windows get gentler morning sun; Iowa State Extension notes a bright east or west window can be a good candidate.
North facing windows rarely provide enough direct light for herbs on their own.

Buildings, trees, awnings and window screens all cut light, so a south window on a narrow street may behave like a medium spot. Winter sun is lower and weaker too, so a window that works in June may fall short in December.

Two quick checks

The shadow test. At midday, hold your hand about a foot above where the pot will sit. A crisp, sharp edged shadow means direct light. A soft, blurry shadow means bright indirect light. Barely any shadow means the spot is too dim for herbs without help.
Count the hours. Check the spot a few times across one day and note when direct sun arrives and leaves.

How to identify insufficient light

Long gaps between leaves and thin stems that lean hard toward the window
Pale, small new leaves
Growth that stalls even though the plant is watered and the roots look healthy
Soil that stays wet for days, because a plant in low light uses less water

That last sign matters because it leads people to overwater a plant that actually needs more light.

Which herbs perform best indoors

Herbs are not equally demanding. Penn State Extension lists chives and lemon balm among herbs that can manage with roughly two to six hours of direct sun, while rosemary and thyme want full sun. Basil grows well indoors with strong light and warmth; University of Maryland Extension notes it can be grown indoors year round.

More forgiving of lower light: chives, mint, parsley, lemon balm
Need strong light: basil, rosemary, thyme, oregano

If your best window is modest, start with the forgiving group and add the demanding herbs once you have a grow light.

When grow lights are needed

Your only windows face north or are shaded by buildings or trees
Your best spot gets less than about six hours of direct sun
You want to keep basil and other sun lovers growing through short winter days
Your herbs show the low light signs above even in your brightest window

Choosing supplemental lighting

You do not need an expensive system. What matters most is that the light is designed for growing, sits close to the plants and runs long enough.

LED grow lights are the most common choice today. Look for lights sold for plant growth, often labeled full spectrum, in a size that covers your pots.
Fluorescent tubes still work well. Several university guides, including Iowa State, describe herbs grown 6 to 12 inches below two 40 watt cool white fluorescent bulbs.
Distance: Iowa State suggests keeping lights within 6 to 12 inches of the leaves. Raise the light as plants grow so the distance stays steady.
Hours: plug the light into an outlet timer set for 12 to 16 hours a day, which gives plants a regular dark period.

Mixing window light and a grow light

You do not have to choose one or the other. An archived University of Missouri Extension guide suggested roughly two hours of fluorescent light for every hour of sun a plant is missing. Treat that as a starting point and watch how your plants respond.

Common lighting mistakes

Judging light by how bright the room feels
Hanging the light two or three feet above the plants, where its intensity drops off
Leaving a grow light on around the clock
Forgetting that winter sun is lower and weaker
Not rotating pots, so plants lean and grow lopsided

For the other mistakes that trip up beginners, read 7 Indoor Gardening Mistakes Beginners Make (And How to Fix Them). For a specific herb, start with How to Grow Basil Indoors in an Apartment.

Putting it into practice

If your apartment barely gets direct sun, our book Grow More From the Space You Have includes a chapter on when a grow light is actually needed and how to set one up safely.

Not sure what light you have yet? The free 7 Day Indoor Garden Starter walks you through the shadow test and an hour count, one short task a day.

Sources

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