LED lighting for plants: how to choose and use the ideal lamp?

Indoors, light is a rare commodity. Between dark corners, short winter days, and windows that filter UV rays, our plants often lack this vital fuel.
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Sommaire

  1. What exactly is a grow light for?
  2. Full spectrum, PAR and PPFD: the light your plants use
  3. What wattage to choose based on the number of plants
  4. How far away to place the light and how many hours a day to run it
  5. LED, HPS or fluorescent: which type of light for your plants
  6. Which light for which plant: a selection chart
  7. How much to budget and how to choose wisely
  8. Common mistakes and how to fix them
  9. Our recommendation for choosing the right light

A grow light reproduces the light spectrum plants need for photosynthesis (400 to 700 nm radiation), allowing you to grow plants where natural light is lacking. Key points to consider before buying:

🌈 Spectrum: full spectrum, with blue light for foliage and red light for flowering.

⚡ Power: 10 to 45 W of LED power is enough for a small indoor plant area.

📏 Distance: 20 to 40 cm above the foliage for a compact LED.

⏱️ Duration: 12 to 16 hours a day, never 24 hours a day.

🪴 Ideal for: seedlings, cuttings, shade-loving plants and winter growing.

Éclairage LED pour plantes : comment choisir et utiliser la lampe idéale ? - Plant and Stories
Slow growth despite the lamp Inappropriate spectrum or non-horticultural lamp Choose a full-spectrum lamp truly dedicated to this purpose. Plant leaning to one side Phototropism Rotate the pot regularly by a quarter turn. Loss of efficiency over time Dirty LED panel Dust the lamp to restore its intensity.

Two simple steps prevent most problems: set a timer to avoid leaving it on 24 hours a day, and ventilate the growing area to prevent overheating. A properly set lamp is easily forgotten and lets the plant do its work.

✅ Our recommendation for choosing

To choose your horticultural lamp properly, summarize your needs in one sentence: how many plants, in what location, and for which growth stage. Then opt for a full-spectrum LED with a power level suited to the area, installed at the right distance and controlled by a timer. This is the safest combination for vigorous plants all year round, even in the middle of winter.

Good lighting is not everything: combined with controlled watering, a suitable growing medium, and a little regular attention, it will lastingly improve the health of your houseplants. It is a modest investment considering the years of growth it offers.

💬 Laura Bruneau's advice
Among my customers, the number one mistake is never the lamp: it is placing it too high and leaving it on for too little time. I have seen monsteras that had stagnated for months regain vigorous growth in two weeks, simply by lowering the lamp to 25 centimeters from the foliage and setting it for 14 hours a day. Choose a decent full-spectrum lamp, then adjust the distance and duration: that is where it all happens.

Laura Bruneau

Jardinière & autrice

Autrice de « Permaculture d'intérieur » (Éditions Rustica) et animatrice de la communauté Instagram @le_jardin_de_laura, Laura Bruneau cultive et teste ses plantes d'intérieur comme d'extérieur. Elle partage sur Plant & Stories des conseils concrets, testés et sourcés.
En savoir plus sur Laura Bruneau
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Grow light

Frequently Asked Questions

Which grow light should I choose for indoor plants?

For most houseplants, choose a full-spectrum LED grow light: it uses little energy, produces little heat and supports everything from germination to flowering. A 10–45-watt light is enough for a small group of plants. Check that the manufacturer specifies a full spectrum and, ideally, provides a PPFD rating or coverage area.

How far should a grow light be from the plants?

For a compact LED lamp, allow 20 to 40 cm above the foliage. Move it closer for seedlings and farther away for more powerful panels and heat-generating HPS lamps. The RHS recommends around 60 cm above seedlings for fluorescent tubes. Observe the plant: scorched leaves mean it’s too close, while stretched stems mean it’s too far away.

How many hours a day should a grow light be on?

On average, 12 to 16 hours a day, depending on the phase: 14 to 16 hours for seedlings and growth, around 12 hours for flowering, and 10 to 12 hours for winter maintenance of tropical plants. Never leave the light on 24 hours a day: plants need darkness. A timer automates the cycles.

What is the difference between a standard LED and a horticultural LED?

A standard LED provides light for the human eye, while a horticultural LED is tuned to the wavelengths useful for photosynthesis (400 to 700 nm), with precise amounts of blue and red light. It is this tailored spectrum, not simply brightness, that allows a plant to grow under artificial light.

Is a grow light really useful in winter?

Yes. In winter, daylight hours and light intensity drop sharply, especially indoors where natural light is limited. A grow light makes up for this lack, limits leaf drop and halted growth, and keeps plants active. This is one of the situations in which it provides the most visible benefits.

What wattage grow light do I need for a few plants?

For one to three plants that need supplemental light, a 10- to 25-watt LED is sufficient. For a shelf or a small green corner, aim for 25 to 45 watts. For lots of seedlings or light-hungry plants, allow 30 to 50 watts of LED per square meter. There’s no need to go for several hundred watts; those are reserved for greenhouses and grow rooms.

Is the full spectrum essential for a grow light?

For versatile indoor use, yes: a full spectrum combines blue light (foliage) and red light (flowering), making it suitable for most plants from growth through flowering. Adjustable-spectrum lights are available to fine-tune lighting for each stage, but they are mainly aimed at enthusiasts. Full spectrum remains the best starting point.

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