Often yes. A plain white LED fixture will raise seedlings as long as it puts out enough light and hangs close to the leaves. A regular LED grow light setup built from hardware store parts starts tomatoes and peppers, and the plants cannot tell which box the fixture came in. What usually stalls seedlings under lamps is too little light, not the wrong shade of white.
"That's a shop light, not a grow light," my neighbor told me, tapping the 4-foot (1.2 m) LED shop fixture I had bolted to a garage shelf. The box showed a workbench and said nothing about plants. Six weeks later the pepper starts under it were stocky and dark green, thick enough in the stem that I had to pot them up early.
The label does buy you something real. A grow lamp supplies a spectrum with more photons a leaf can use for photosynthesis, so the same electricity does a bit more work. But Jonathan Ebba at UNH Extension points to quantity as the usual problem. That means intensity and duration, not spectrum. Pick an LED shop light for plants that is bright, leave it on long enough, and you have handled the part that decides the outcome.
Here is the spec worth copying. Use a 4-foot plug-in shop fixture sold as full spectrum daylight, rated at 3,000 lumens or more, hung 12 to 24 inches (30 to 61 cm) above the foliage and run 14 hours a day on a cheap timer. If you have grown under fluorescent tubes before, that old habit of dropping the fixture to 6 to 12 inches (15 to 30 cm) does not carry over to LEDs.
Height does more work here than price does. Raise the same fixture toward the top of that range and the light hitting each leaf drops off fast, so treat the hanging distance as seriously as you treat the lumen rating. Seedlings that stretch and lean are asking to be moved closer. Start near the bottom of the range and lift the bar as the plants grow.
The numbers printed on most fixtures are the wrong numbers. Watts tell you the energy the lamp uses, and lumens describe light the way a human eye sees it. Neither one counts the light a leaf can turn into growth. The measure that does is PPFD, in micromoles per square meter per second. It only counts when you take it at foliage level, where your trays sit, since a reading at the bulb tells you nothing about the seedlings below.
Photon efficacy is the other number worth hunting for. It is written in micromoles per joule, and it tells you how much usable light a fixture makes per unit of energy. Fixtures built for greenhouse work reach 2.5 to 2.8. The floor for products listed by the DesignLights Consortium is 1.9. That floor covers listed horticultural gear, not the household LED on your garage shelf, so read it as a benchmark and not a promise.
A grow light label earns its price when the box backs it with PPFD or efficacy figures you can check. When the packaging offers watts and a purple stock photo, buy the bright 4-foot shop fixture instead and put the difference into a timer. Your seedlings answer within a couple of weeks. Short, thick stems mean the light is doing its job, and pale stretched ones mean you need to drop the bar lower.
Read the full article: Grow Lights for Indoor Plants: What Really Works
