← the journal/guide · 29 apr 2026
grow lights: what actually matters and what's just purple
the dark-room squad — photons are photons
a grow light is worth it when no spot in your home passes the shadow test — no fuzzy hand shadow at midday means too dark for most plants. what matters: a full-spectrum white LED bulb, positioned 30–60cm above the plant, running 10–12 hours a day on a timer. an ordinary e27 full-spectrum bulb in a normal lamp fixture (under €20 total) covers a few plants; purple light, 'plant-specific spectrums' at this scale, and high wattage claims are mostly marketing.
- 1. symptom
every plant in that room slowly gives up, regardless of care
you've tried the 'low light tolerant' list. the snake plant survives but hasn't grown in a year, the pothos is a pale noodle, and everything else has quietly died. the room fails the shadow test: at midday, your hand casts no real shadow anywhere. no watering technique fixes a photon shortage — plants eat light, and this room serves nothing.
- 2. cause
winter, north windows, and the brutal math of distance
indoor light is weaker than it looks (your eyes auto-correct), it collapses with distance from the window, and in northern-european winter even a decent window delivers a fraction of what most houseplants evolved under. some rooms simply do not contain enough light for photosynthesis-as-a-lifestyle. that's not a plant-care failure — it's physics, and physics responds well to lamps.
- 3. the fix
full-spectrum white led, close, long, and on a timer
buy a full-spectrum white LED grow bulb that fits a standard socket — they look like normal bright-white bulbs and cost €10–25. screw it into any lamp you can aim: desk lamp, floor reader, clamp light. hang or aim it 30–60cm above the foliage — distance matters enormously; light intensity drops off fast, so twice the distance is roughly a quarter the light. run it 10–12 hours a day on a cheap plug timer (consistency beats intensity, and nobody remembers to switch a lamp on daily forever). that's the entire setup. one bulb covers a plant or three; a small LED panel covers a shelf.
the spec that matters and the specs that don't
matters: full spectrum (continuous white light — plants use mostly red and blue, but white LEDs contain both plus everything between, and you can stand to look at them), actual brightness (for the curious: growers measure PPFD, but at houseplant scale 'a bright bulb, close enough' gets you there), distance, and daily hours. doesn't matter much: the purple/pink 'blurple' aesthetic — those panels work but aren't better than white LEDs, they just look like a sci-fi crime scene in your living room. mostly nonsense: 'NASA spectrum' branding, wattage-equivalent claims ('600W!' on a 60W panel), and anything implying a special light makes plants grow faster than a good ordinary one. photons are photons; plants can't read the box.
when it's worth it (and when it isn't)
worth it: rooms that fail the shadow test, dark winters when even your bright windows go dim from november to february (a grow light as winter supplement keeps plants from going backwards), and propagation stations — cuttings root faster under consistent light. not worth it: fixing a plant whose problem is watering (a lamp won't pump out a swamp), or forcing a sun-worshipper to live in a windowless bathroom — a cactus under one small bulb is on life support, not thriving. the honest framing: a grow light turns a 'plants survive here' room into a 'plants grow here' room. it doesn't turn a basement into a greenhouse.
the setup i actually run
one e27 full-spectrum bulb (€12) in a thrift-store gooseneck lamp, aimed at the dark-corner shelf, timer set 8am to 7pm. that's it. the pothos that spent a year sulking there put out six new leaves in two months — same plant, same pot, same watering, just photons. two warnings from experience: plants near a grow light drink faster, so re-learn their thirst; and don't run lights 24/7 out of enthusiasm — plants need a night cycle too. twelve hours is generosity. eighteen is an interrogation.
people keep asking…
- do i need a grow light for my houseplants?
- only if no spot passes the shadow test: hold your hand 30cm over the plant area at midday — no visible soft shadow means too dark for most plants. if you have a bright window, you don't need one (except possibly as a winter supplement).
- what kind of grow light is best for beginners?
- a full-spectrum white LED bulb in a standard socket, in any lamp you can aim. it's cheap (€10–25), looks like normal light, and works as well as specialty panels at houseplant scale. add a plug timer for 10–12 hours a day.
- how far should a grow light be from my plants?
- roughly 30–60cm above the foliage for a typical LED bulb. closer is stronger — intensity drops off steeply with distance — but watch for heat or bleaching on the nearest leaves and back off if you see it.
- are purple grow lights better than white ones?
- no. purple 'blurple' panels emit mostly red and blue, which plants do use — but full-spectrum white LEDs contain those wavelengths too, render your room livable, and perform just as well for houseplants. the purple is aesthetic, not advantage.
the weekly entry
real plant talk. once a week.
no fluff. just the stuff we all wish we knew sooner.
unsubscribe anytime. your inbox, your rules.