I work in quality at Signify, which means I spend my days reviewing lighting products before they reach customers—roughly 200 different fixtures, drivers, and controls a year. In 2024, I rejected just under 3% of first submissions for spec deviations.
The job has taught me a fair amount about how people buy lighting. And if there's one question that tells me a purchase is heading for trouble, it's this:
Can you start seeds indoors without a grow light?
It sounds like a simple question. It isn't. Hidden inside it is the assumption that a bulb is a bulb—that "bright enough" is a specification. That same assumption leads people to buy the wrong spotlight bulbs, the wrong COB downlights, and the wrong smart lighting systems. So let's talk about why.
Why "bright enough" isn't a specification
It's tempting to compare lighting products by the three numbers on the box: lumens, watts, price. Higher lumens, lower watts, lower price. Objectively better, right?
Not exactly.
Take a COB downlight. Two fixtures advertise 3,500 lumens and 40 watts. Same color temperature on paper. One costs $18, the other $55. The $18 one looks like a smarter choice until you install it and discover it flickers at 30% dimming, its driver dies at 8,000 hours rather than 50,000, and its beam is so wide that half the light lands on the wall instead of the counter. I've reviewed both types. The numbers on the box were accurate. The performance was not "the same."
The same principle applies to seeds. A regular spotlight bulb can start seeds indoors—or rather, it might start them, depending on the bulb, the distance, and what you're growing. But the word "can" hides all the variables that determine whether you'll get healthy seedlings or a tray of pale, leggy stems.
Plants don't care about lumens, which measure how bright something looks to a human eye. They care about photons hitting the leaf surface—specifically, photons in the wavelengths that drive photosynthesis. The McCree curve, which plant scientists have referenced since the 1970s, shows peaks in the blue and red parts of the spectrum. That's why horticulture lighting has its own metrics: PPFD for intensity, DLI for cumulative daily light. "It looks bright" isn't a metric.
Let me rephrase that: if you're starting seeds under a household bulb, the question isn't "is it bright enough?" It's "does this light deliver enough usable photons, at the distance of the leaves, for the number of hours the seedlings need?" Those are very different questions with very different answers.
What a spec sheet doesn't tell you
In my line of work, most product failures are quiet ones. A fixture doesn't stop working on day one—it degrades, flickers, or drifts in color over months. By the time anyone notices, the warranty window is closing and the fixtures are already buried in a ceiling.
We rejected a batch of downlights in Q1 2024 because the correlated color temperature was off by about 500K from the approved sample. The vendor argued it was within industry tolerance. He was probably right—technically. But "within tolerance" doesn't stop a customer from seeing that half the fixtures in a row look warmer than the other half. That inconsistency is what damages a space, and a brand.
You can't see any of that in a product photo. You can't see thermal design, LED binning, driver components, or solder joints. You can't see flicker in a comparison chart. An $18 COB downlight and a $55 one can look identical in a screenshot and perform completely differently over five years.
To be fair, cheaper fixtures have their place. I understand why someone specs them for a temporary installation or a budget-constrained project. But for a commercial space that runs ten hours a day, the cost of failure isn't the fixture price—it's the labor to replace it, the downtime, and the client's perception.
When I evaluate a product, I look for the data that predicts long-term behavior: IES LM-80 reports for lumen maintenance, driver specifications, and warranty terms. If a manufacturer doesn't publish those, or gets vague when asked about them, that's information in itself.
The smart lighting boundary
A different version of "a bulb is a bulb" is the belief that consumer lighting and professional lighting are interchangeable. This comes up a lot with smart lighting.
People ask me whether a Signify Hue update will add some feature to a commercial project, or whether they can save money by wiring a residential smart system into a retail space. The honest answer is: no—and not because the consumer product is bad. Philips Hue is a genuinely good home ecosystem, and its regular updates bring real improvements to the home experience. But a retail or office space has different requirements: integration with building controls, compliance with emergency lighting codes, remote maintenance, and the expectation of 50,000+ hours of operation. Signify smart lighting for professional spaces is built around platforms like Interact, which is a completely different engineering and support commitment from a home system.
The same logic applies to buying components for your own project. You can save money by mixing consumer drivers, controls, and fixtures from different brands. It might even work—for a while. Then a firmware update changes one device's behavior, or a warranty claim is denied because the product wasn't installed in the intended configuration, or an inspector asks for documentation nobody can provide. The word "compatible" does a lot of heavy lifting in those conversations.
What "saving money" actually costs
A few years ago, a retail client wanted to cut costs on a renovation. They swapped the specified COB downlights for a cheaper alternative—roughly $200 in savings on the order. After installation, the store manager started getting complaints from staff about headaches. The new fixtures had visible flicker at the dimming level they used. Nobody had specified flicker, so nobody caught it until people worked under those lights all day.
The fixtures had to be replaced. Labor plus new fixtures came to about $1,800 more than the premium option originally specified. The store also lost a week of full lighting during the redo. I want to say the total was closer to $2,400 once the electrician's second trip was factored in, but don't quote me on the exact figure. The pattern is what matters: a $200 saving turned into a multi-thousand-dollar loss.
In horticulture, the same pattern shows up as a season lost. I once worked with a startup that was starting 200 trays of seedlings under regular spotlight bulbs—I think they were 60-watt equivalents. "It's bright enough," the owner told me. It wasn't. The seedlings stretched toward whatever light they could get, producing weak, leggy growth that would never survive transplanting. They threw out the trays and restarted. The money they saved by not buying proper horticulture lights was small; the six-week delay pushed them past their planting target entirely.
Ask the better question
Here's the shortcut I use when reviewing products, and it works for purchasers too: start with the outcome, not the product.
- For seeds: set a PPFD target for your seedlings—most common vegetables want something like 150 to 300 μmol/m²/s for 14 to 16 hours a day—then measure what a given light actually delivers at the distance of the leaves. If a regular bulb meets the target, you don't need a grow light. If it doesn't, no amount of "it looks bright" will fix it.
- For spaces: define the experience before you look at fixtures: CRI, glare, beam angles, controls integration, and the emergency lighting code that applies to your building. These constraints narrow the options better than a budget does.
- For systems: match the ecosystem to the application. A consumer smart system and a professional networked system are not interchangeable, even if both "light up" the same room.
And if a supplier tells you a project isn't their specialty, pay attention. The vendor who says "this isn't our strength—here's who does it better" earns my trust for everything else. We hold ourselves to that standard at Signify: we make professional lighting, controls, and horticulture systems, but we don't pretend to be the right answer for every application on earth. A specialist who knows their limits is more credible on the projects inside them.
So—can you start seeds indoors without a grow light? Yes, if the numbers work. No, if they don't. The light doesn't care what it's called. It either delivers what the plant needs or it doesn't. The better question, the one I wish every buyer asked first, is: what does this application actually need from the light, and does this product deliver it? Get that right, and the rest of the decision gets a lot simpler.