Most houseplants do fine with window light from spring through early fall. Once you have a dim room, a north window, or the short days of a Northeast or Midwest winter, a grow light makes up the difference.
For most homes, I’d pick a full-spectrum white LED grow light, set 6 to 12 inches above the leaves and run 12 to 16 hours a day on a timer. It’s efficient, runs cool, and looks like normal room light.
Match the light’s shape to your space: a bulb or clip-on lamp for one plant, bars for a shelf, and a panel for a group. Then check the plant every week or two and adjust the height.
Grow lights for indoor plants work best when you treat them as an adjustable tool and keep fine-tuning the setup.
When Does an Indoor Plant Need a Grow Light?
A plant needs a grow light when its spot can’t give it enough light to keep growing at a normal pace.
The plant will show you this through its shape and new leaves, and the season and the room’s layout make the gap bigger or smaller.
Signs That Window Light Isn’t Enough
Stretching is the clearest sign. Stems grow long and thin with wide gaps between leaves, and the whole plant leans hard toward the window. If you are stocking up, a grow light is the first thing I would pick up.
Watch for these other signs too:
- New leaves come in smaller than the old ones.
- Variegated leaves fade back to plain green.
- Flowering plants like African violets stop blooming.
- Growth stalls during the season when the plant should be active.
- Soil stays wet for days, because a plant in dim light uses water slowly.
If you see two or more of these, I’d add light before you change anything else.
Dark Rooms and Short Winter Days
Light fades fast as you move away from glass. A plant on the sill can get several times more light than the same plant 6 feet back in the room. A north window gives the least, and a basement or windowless office gives almost none.
Winter makes this worse. In northern states, the sun sits lower and the days are shorter, so a south window that gets six hours of direct sun in June might get two weak hours in December.
Long gray stretches in the Pacific Northwest and the Great Lakes region cut light even more. If you garden there, I’d plan on grow lights from about November through February even for tough plants.
If you’d rather skip lights, some indoor plants that don’t need sun handle dim rooms better than others.
Which Type of Grow Light Fits Your Space?
The right type depends on how many plants you’re lighting and how they’re arranged. Screw-in bulbs and clip-on lamps suit single pots, bars and strips cover shelves, and panels spread light over a group.
All of the best grow lights for indoor plants today are LEDs, because they use less power and give off less heat than older fluorescent tubes.
LED Bulbs and Clip-On Lamps for Individual Plants
A full-spectrum LED bulb fits a standard lamp socket. That makes it the easiest way to light one fiddle-leaf fig or a pot of herbs, and you can keep using a floor lamp you already own.
Clip-on lamps have flexible goosenecks that clamp to a shelf edge or desk. They’re cheap and handy for small plants.
Most clip-ons are low wattage, though. They work best within about 12 inches of the leaves and cover a circle only about as wide as one pot.
LED Bars and Strips for Shelves
LED bars and grow light strips are thin, flat lights that mount under the shelf above your plants. Their long shape spreads light evenly along the whole shelf.
I like them for wire racks and bookcases. They tuck out of sight and keep the light close to the leaves. Many come in kits of two to four bars with one shared timer.
Panels for Wider Coverage
LED panels are square or rectangular fixtures that hang or sit on a stand above a group of plants. They put out more light over a wider area than bars or bulbs.
A panel makes sense for a cluster of succulents, a tray of seedlings, or a grouping of large tropicals. Expect it to need more height and more room overhead than other types.
Are Fluorescent Tubes Still Worth Using?
Fluorescent tubes still grow plants just fine, especially seedlings. If you already own a shop light fitted with T5 or T8 tubes, use it.
For a new purchase, I’d pick LED. LEDs last longer, use less electricity, and run cooler, so leaves are less likely to scorch. Fluorescent tubes also contain a small amount of mercury, so they need careful disposal.
What Does Full-Spectrum Light Mean for Plants?
A full-spectrum grow light gives off a balanced mix of colors across the range plants use, a lot like sunlight. For houseplants that will live under the light for months, full-spectrum lighting supports steady, healthy growth.
White Light vs. Purple Light
Older grow lights mostly used only red and blue diodes, which mix into a pink or purple glow. That glow grows plants, but it’s harsh in a living room and makes it hard to spot pests or yellow leaves.
A full-spectrum white LED looks like ordinary daylight. It includes the red and blue that plants rely on, plus green and other colors that help you see the true color of your plants.
I’d choose white light for any plant you live with. Look for a color temperature between about 4000K and 6500K on the box. Lower numbers look warmer, and higher numbers look cooler and bluer.
How Red and Blue Light Support Photosynthesis
Photosynthesis is how plants turn light into the sugars they need to grow. Chlorophyll absorbs blue light and red light most strongly.
Blue light helps keep plants compact, with sturdy stems and thick leaves. Red light drives growth and helps trigger flowering and fruiting.
A full-spectrum LED grow light gives both. Plants also use some green light, which reaches lower leaves better than red or blue. That’s one reason a balanced white spectrum works well for leafy houseplants.
Which Light Specifications Actually Matter?
The numbers that tell you most about a grow light are the ones that measure plant-usable light where the leaves are. Watts and lumens show up on every box, but they say little about how a plant will grow.
PAR, PPF, and PPFD in Plain English
PAR stands for photosynthetically active radiation. It’s the band of light plants use, from about 400 to 700 nanometers.
PPF is the total amount of PAR light a fixture puts out each second. Think of it as how much plant-usable light leaves the lamp.
PPFD measures how much of that light lands on a small area each second, written as µmol/m²/s. It’s the most useful number, because it tells you what your plant receives at a given distance.
As rough targets, low-light foliage plants are happy around 50 to 150 PPFD. Bright-light tropicals and herbs want around 150 to 300. Succulents and seedlings do best near 200 to 400.
Why Watts and Lumens Don’t Tell the Whole Story
Watts measure electricity used, not light delivered. Two 20-watt lights can put out very different amounts of usable light depending on how efficient they are.
Lumens measure brightness as human eyes see it. Our eyes are most sensitive to green and yellow, while plants lean on red and blue. A bulb with high lumens can still give a plant less usable light than you’d expect.
Watch out for “equivalent” wattage claims, too. A light marketed as “1000W equivalent” might draw only 60 to 100 watts from the outlet.
How to Check a Light’s Coverage at Canopy Height
The canopy is the top layer of leaves. Good brands publish a PPFD map showing readings at several heights, such as 6, 12, and 18 inches, across the light’s footprint.
Readings drop toward the edges of that map. If the center shows 300 and the corners show 90, plants at the corners will grow slower.
Without a PAR meter, a free phone lux app gives a rough comparison between spots. Compare the readings with each other, and don’t read them as exact numbers.
How Do You Match a Light to Your Plant?
Match the light to how much sun the plant gets in nature. Shade plants need gentle light, desert plants need strong light, and edible plants and seedlings need strong light for many hours.
Foliage Houseplants
Pothos, philodendrons, snake plants, ZZ plants, and peace lilies come from forest floors or tolerate shade. A single LED bulb or a clip-on lamp, set 12 to 24 inches above the leaves, keeps most of them growing well.
Tropicals that like bright indirect light, such as monstera and rubber plants, need more. I’d give them a bulb or bar at 12 to 18 inches, or a panel for a big plant.
For more options, my guide to indoor plants with big leaves covers which ones need extra light.