We are a seed company, not a lighting company, and that is exactly why this guide exists. At HOME GROWN we run germination tests and start trays of heirloom seedlings every week of the year, and from October through March in Oregon, every one of those trays lives under an artificial light. We have burned seedlings by hanging lights too close, grown pale spindly lettuce by hanging them too far, and learned what the spec sheets actually mean the hard way.
This guide skips the brand roundup. Instead, it gives you the four numbers that matter on any grow light box, light targets for each type of plant, a distance chart, and the three setups we actually use. Once you understand PPFD and photoperiod, you can pick a good light at any store in ten minutes.
The short answer
If you want the one-paragraph version: buy a full-spectrum white LED fixture sized to your space, hang it so your plants receive the PPFD listed in the table below, and run it 12 to 16 hours a day on a cheap outlet timer. A 20 to 40 watt LED shop light covers a shelf of herbs or seedlings. A 100 to 150 watt panel covers a 2 by 2 foot plant corner. Skip incandescent "grow bulbs" entirely, and treat purple-pink "blurple" LEDs as optional, not better.
Everything below explains why, so you can adapt those defaults to your plants.
The four specs that actually matter
Grow light marketing leans on big wattage claims and vague words like "sunlike." Ignore those and read for these four numbers.
PPFD: how much light reaches the plant
PAR (photosynthetically active radiation) is the slice of light plants use for photosynthesis, roughly the 400 to 700 nanometer range. PPFD (photosynthetic photon flux density) measures how much of that light actually lands on a square meter of leaf every second, in micromoles per square meter per second (µmol/m²/s). It is the single most useful spec, because it changes with distance: the same lamp might deliver 600 µmol/m²/s at 6 inches and 150 at 24 inches. Good manufacturers publish a PPFD map showing intensity at several heights. If a light lists no PPFD data at all, that tells you something too.
Lumens and lux: a rough backup
Lumens measure brightness as human eyes see it, weighted toward green and yellow. They are not a plant metric, but for white LEDs they work as a rough proxy when PPFD is missing. If you have a lux meter or a phone app, a usable approximation for white LED light is PPFD ≈ lux × 0.015. So a reading of 10,000 lux is roughly 150 µmol/m²/s. Treat it as an estimate, not a lab measurement.
Color temperature: leafy vs. flowering
Kelvin describes the tint of white light. Cool daylight tones around 5000 to 6500K favor compact leafy growth, which is what seedlings, lettuce, and herbs want. Warmer light around 3000K carries more red, which supports flowering and fruiting. Full-spectrum white fixtures cover both jobs well enough for home growing, which is why we default to them. The purple blurple lights work, but they make it hard to see whether your leaves are yellowing, and you live with the glow.
Efficacy and wattage: your power bill
Efficacy, in µmol per joule, tells you how much plant-usable light you get per watt. Quality LEDs in 2026 deliver roughly 2.0 to 2.8 µmol/J; T5 fluorescents manage about half that. As a sizing rule of thumb, plan on 10 to 20 actual watts of LED per square foot for foliage plants, 20 to 30 for seedlings, greens, and herbs, and 30 to 40 for fruiting vegetables. Note "actual draw" watts, not the inflated "equivalent" number on the front of the box.
How much light do your plants need?
Different plants want very different amounts of light, and most grow light disappointments come from mismatching the two. These targets are consistent with university extension guidance, including the University of Minnesota Extension's guide to lighting for indoor plants and seed starting.
| Plant type | PPFD target (µmol/m²/s) | Hours per day | Examples |
|---|---|---|---|
| Low-light foliage | 50 to 150 | 8 to 12 | Pothos, snake plant, ZZ plant |
| Medium-light tropicals | 150 to 300 | 10 to 12 | Monstera, philodendron, ferns |
| High-light plants and succulents | 300 to 500 | 12 to 14 | Succulents, cacti, citrus |
| Seedlings and leafy greens | 200 to 400 | 14 to 16 | Lettuce, kale, herb and vegetable seedlings |
| Fruiting vegetables | 400 to 600 | 12 to 16 | Tomatoes, peppers |
Researchers often combine intensity and duration into a daily light integral (DLI), the total moles of light per square meter per day. Vegetable seedlings do best around 12 to 16 mol/m²/day. The math is friendly: 250 µmol/m²/s for 16 hours works out to about 14.4 mol, right in the sweet spot. That is why a moderate light running longer often beats a strong light running briefly.
One more number worth knowing: darkness. Plants need a real night to complete normal growth processes. Give everything at least 8 hours of dark, and never run lights 24/7.
Types of grow lights compared
| Type | Efficacy | Lifespan | Best for |
|---|---|---|---|
| Full-spectrum white LED | 2.0 to 2.8 µmol/J | 25,000 to 50,000 hrs | Nearly everything; our default |
| T5 fluorescent | 1.0 to 1.3 µmol/J | 10,000 to 20,000 hrs | Budget seed starting; output fades with age |
| HID (metal halide, HPS) | 1.0 to 1.7 µmol/J | 10,000 to 24,000 hrs | Large dedicated grow rooms; runs hot |
| Incandescent "grow bulbs" | Very low | 1,000 hrs | Nothing; most energy becomes heat |
LEDs win on running cost, heat, and lifespan, which is why they have effectively replaced everything else for home growing. Fluorescent T5 fixtures still start seeds perfectly well if you already own them; just remember tube output declines noticeably after a year or two of heavy use, even though the tube still lights up. If you are buying new in 2026, buy LED.
How far should a grow light be from your plants?
Distance is the free dial that turns one light into many intensities. Closer means more PPFD, farther means less, and the falloff is steep. Typical starting points:
| Fixture | Seedlings and greens | Established houseplants |
|---|---|---|
| T5 fluorescent tube | 3 to 4 inches | 6 to 12 inches |
| 20 to 40 W LED strip or shop light | 6 to 12 inches | 12 to 18 inches |
| 100 to 150 W LED panel | 12 to 18 inches (dim if possible) | 18 to 24 inches |
| 200 W and up panel | 18 to 24 inches | 24 inches or more |
Treat these as starting points, then let the plants vote. Too close: bleached or crispy patches on top leaves, curling, compact scorched growth. Too far: stems stretching toward the light, wide gaps between leaves, pale color, and seedlings that flop. Stretching is the most common failure we see in customer photos; if your seedlings look like bean sprouts, the light is too weak or too distant. Our guide on how to fix leggy seedlings covers the rescue steps.
Raise the light as plants grow to hold the distance steady. Adjustable pulley hangers or a rack with movable shelves make this a ten-second job.
How long should grow lights be on?
Buy a $10 outlet timer the same day you buy the light. Consistency matters more than perfection.
- Seedlings and leafy greens: 14 to 16 hours a day
- Herbs and high-light houseplants: 12 to 14 hours
- Medium-light tropicals: 10 to 12 hours
- Low-light foliage plants: 8 to 12 hours
- Everything: at least 8 hours of darkness every night
If a plant also gets decent window light, run the grow light fewer hours as a supplement, for example 6 to 8 hours bridging the dark ends of a winter day.
Three setups we actually use
1. The seed-starting rack
A wire shelving unit, one 4-foot full-spectrum LED shop light per shelf hung on small chains, and a timer set to 16 hours. Lights start 6 inches above the trays and rise as seedlings grow. This is the workhorse behind every spring garden we grow, and it is cheap to build. If seed starting is your main goal, our dedicated guide to grow lights for seed starting goes deeper on trays, heights, and schedules, and our tips for starting seeds indoors cover the rest of the process.
2. The kitchen herb shelf
Basil, cilantro, and parsley are the easiest wins under lights: a single 20 to 40 watt LED strip 8 to 12 inches above the pots, 12 to 14 hours a day, gives you cuttable herbs all winter. Genovese basil and cilantro germinate fast and forgive beginners. Start with our easiest herbs to grow indoors list, or grab an all-in-one kit if you want pots, soil, and seed in one box.
3. The dark-corner houseplant light
For a plant corner with no window, one 100 to 150 watt full-spectrum panel 18 to 24 inches above the canopy, 10 to 12 hours a day, keeps a cluster of medium-light tropicals healthy. Pendant-style white LED fixtures do the same job for a single statement plant without looking like lab equipment. Pair good light with good watering habits; our guide to taking care of plants in a plant pot covers the container side.
Common mistakes to avoid
- Buying by "equivalent watts." Size by actual draw and PPFD, not marketing equivalents.
- Hanging one height all season. PPFD changes fast with distance; adjust as plants grow.
- Running lights around the clock. No dark period stresses plants. Eight hours minimum.
- Expecting fruit from a weak light. A 20 watt strip grows lettuce, not tomatoes. Fruiting crops need 400+ µmol/m²/s.
- Ignoring heat on fluorescents and HID. Check leaf-level temperature with your hand: if it feels warm after a minute, raise the fixture.
Grow light FAQ
Can a regular LED bulb work as a grow light? For a low-light foliage plant, yes. A bright 5000K household LED bulb (about 9 to 12 actual watts) in a clamp lamp 6 to 12 inches away is real usable light. It will not carry herbs, seedlings, or anything fruiting.
Are purple lights better than white? No for most home growers. Red-blue diodes are efficient on paper, but full-spectrum white grows plants just as well at home, renders leaf color accurately so you can spot problems, and is far easier to live with.
How much does a grow light cost to run? A 40 watt LED running 16 hours a day uses about 19 kWh a month, roughly $3 at $0.16 per kWh. Even a 150 watt panel on 12 hours runs about $9 a month. Efficacy is why LED pays for itself.
Do seedlings need a special seedling light? No. They need 200 to 400 µmol/m²/s for 14 to 16 hours. Any full-spectrum fixture that delivers that at a workable height qualifies.
Can I grow vegetables to harvest entirely indoors? Leafy crops, absolutely; fruiting crops need more hardware. See our guide to the best vegetables to grow indoors for realistic picks.
The light is half the equation
A good light earns its keep only when there is something worth growing under it. Winter is when a grow light turns from a gadget into a fresh-food tool: a shelf of heirloom lettuce, a pot of basil, trays of spring transplants that hit the garden weeks ahead of your neighbors.
Start with what you like to eat. Our heirloom vegetable seeds include compact lettuces, kales, and greens that thrive under exactly the setups above, and our herb seed collection covers every kitchen staple. If you would rather start with everything in one box, our starter kits and grow guides pair seed with step-by-step instructions. Everything ships from HOME GROWN, and every variety is open-pollinated, so you can save seed from what you grow.
