Why Seedling Lighting Is Different
Seedlings are not miniature versions of mature plants. They have different light requirements, and getting this wrong is one of the most common reasons for leggy, stretched, weak growth at the start of the season.
Mature plants in full growth need a PPFD (photosynthetic photon flux density) of 400 to 600 µmol/m²/s or more. Seedlings are far more sensitive. The target range for germinated seedlings is roughly 150 to 300 µmol/m²/s. Push much beyond that with a bright panel at close range and you can bleach the leaves. Drop too low and they stretch toward the light, growing thin and floppy before they have any real root structure.
The other factor is spectrum. For seedlings and vegetative growth you want a cooler, blue-weighted light in the 5000K to 6500K range. That cooler temperature keeps internode spacing tight, which is exactly what you want in the early weeks. Flowering lights heavy in red wavelengths are not what you need at this stage.
Duration matters too. Most seedlings do well on 14 to 16 hours of light per day. A timer is not optional; it is part of the setup.
I run a multi-tier propagation shelf with Barrina T5 strips on each level, plus a 60x60cm tent with Mars Hydro for batches that need a bit more intensity. I have started tomatoes, basil, coriander, chilli seedlings, and various cuttings under both setups. The products below are what I actually recommend, with specs verified against current listings.
If you are shopping for lights for established plants rather than seedlings, see our guide to the best grow lights overall.
The Best Grow Lights for Seedlings
1. Barrina T5 LED Grow Light Strips (2ft, 4-Pack): Best for Shelves and Trays
This is what I use every season and what I recommend to most home growers starting from seed. The Barrina T5 strips are slim, linkable LED tubes designed specifically for shelf-based growing. Buy the 2ft 4-pack and you get four 10W strips — 40W total — that daisy-chain together from a single plug. The design is made for standard wire shelving, which most propagation setups already use.
Wattage: 10W per strip (40W for a 4-pack)
Spectrum: Full spectrum, 5000K
Length: 2ft (60cm) per strip
Configuration: Linkable, plug-and-play, daisy-chain up to 16 strips from one outlet
UK price: Around £25 to £35 for a 4-pack
I run mine about 3 to 4 inches above seedling trays. At that distance the coverage is excellent across a standard propagation tray. Because T5 LED strips run cool, you can get that close without heat stress. For comparison, a traditional T5 fluorescent tube should sit 6 to 12 inches above seedlings; LEDs at this output level can go closer.
The 5000K spectrum is a good match for the vegetative and seedling stage. My tomato seedlings under these lights come up compact and stocky. On a three-tier shelf I have a set on every level. They daisy-chain cleanly, the fixtures clip to wire shelving without any drilling, and the power draw is low enough that running them 15 hours per day adds very little to the electricity bill.
Pros: Low cost, low heat, perfect for shelf trays, daisy-chainable, good seedling output
Cons: Per-strip wattage is modest. Not ideal if you want a single light for a tent.
2. Spider Farmer SF1000: Best for Serious Seedling Batches
The Spider Farmer SF1000 is a 100W quantum board panel using high-efficiency Bridgelux LEDs rated at 2.5 µmol/J. It is the sensible choice when you want a single light that can carry a plant from seedling through vegetative growth without swapping fixtures.
Wattage: 100W
Coverage: 60x60cm (seedling/veg)
Efficiency: 2.5 µmol/J (PPE)
Spectrum: Full spectrum — 3000K, 5000K, 660nm red, IR
Dimmer: Yes, built-in
Price: Around £65 to £75
For seedlings, you run this at reduced intensity — 25 to 50 percent output — and hang it 18 to 24 inches above the canopy. That combination keeps PPFD in the 150 to 300 µmol/m²/s range that seedlings want without light burn. As plants develop and move into vegetative growth, you raise intensity and lower the light gradually.
The dimmability is what makes this work for seedlings specifically. A lot of growers over-light their seedlings by using a flowering panel at full blast. With the SF1000, you dial it back at the start and increase gradually.
Pros: Excellent efficiency, dimmable, covers 60x60cm from seedling through veg, grows with your plants
Cons: More expensive than strip lights; more capability than seedlings alone require
For more on quantum board options, see our guide to the best LED grow lights.
3. Mars Hydro TS600: Best for Tent Growers Starting Seeds
The Mars Hydro TS600 is a 100W full-spectrum panel rated for a 2x2ft coverage area, which maps closely to a 60x60cm tent. I have used the Mars Hydro TS 1000 in my own tent setup and know the brand’s build quality well. The TS600 is the smaller sibling, designed specifically for that compact footprint.
Wattage: 100W
Coverage: 2x2ft (60x60cm)
Peak PPFD at centre (12 inches): 986 µmol/m²/s
Efficiency: 2.0 µmol/J
Spectrum: Full spectrum, 400-700nm with IR
UK price: Around £50 to £80
For seedlings, you hang this 24 to 30 inches above the canopy. At 12 inches the PPFD is nearly 1,000 µmol/m²/s, which is far too intense for seedlings. Pull it up to 24 to 30 inches and you bring that down into a workable range. The 2026 version adds a dimmer knob, which makes managing seedling intensity far easier than relying purely on distance.
Inside a tent the reflective walls boost efficiency significantly. The same light that would give patchy coverage in an open room delivers excellent uniformity when the tent sides bounce photons back at the canopy.
Pros: Good entry-level panel for a 60x60cm tent, handles seedling and vegetative stages, reasonably priced
Cons: Older versions lack a dimmer; efficiency at 2.0 µmol/J is below the Spider Farmer SF1000
If you are running a tent setup and want to understand the full-spectrum side of things, see our full spectrum grow lights guide.
4. GooingTop LED Clip-On Grow Light: Best for Single Plants and Windowsill Starting
Not every seed starting situation calls for a shelf full of strips or a panel in a tent. If you are germinating a few pots on a windowsill or trying to bring on a single tray of herbs on a kitchen counter, the GooingTop clip-on is the sensible tool.
Wattage: 10W
Spectrum: 6000K white LEDs plus 660nm red LEDs, CRI 95
Timer: Built-in 4/8/12-hour auto cycle
Mounting: Flexible gooseneck with desk clamp
Dimmer: 5 brightness levels
The 6000K spectrum is close to midday sunlight in its colour profile, a solid starting point for seedlings. The 660nm red LEDs push photosynthesis at a wavelength plants respond to efficiently. It will not match the output of a panel or a strip setup, but at 10 to 15cm above a single pot or small tray it provides meaningful supplemental light.
The built-in timer is the standout feature at this price point. You clip it on, set it to 14 hours, and it runs on a 24-hour cycle without you touching it again. This is not the light for a full propagation shelf. It is the light for the person starting a dozen tomato plugs on a south-facing windowsill in February where a full shelf setup would be disproportionate.
Pros: Compact, affordable, built-in timer, flexible positioning, no setup required
Cons: Low total output; coverage limited to one or two pots directly underneath
Which Grow Light Should You Buy?
The right choice depends almost entirely on the scale of your seed starting and the setup you are working with.
- Multi-tier propagation shelves: Barrina T5 strips. One 4-pack per shelf level, daisy-chained from a single timer plug. This is the most cost-effective way to light a serious seedling operation and what I run as my main setup.
- A 60x60cm grow tent: Mars Hydro TS600 or Spider Farmer SF1000. Both are 100W panels sized for that footprint. The Spider Farmer is the more efficient choice; the Mars Hydro is often slightly cheaper in the UK.
- A windowsill or kitchen counter: GooingTop clip-on. Low cost, easy to position, timer included.
- Growing in a larger tent: The strips or SF1000 are not sized for that footprint. See our guide to grow lights for indoor plants for options covering bigger spaces.
One thing I have learned across multiple growing seasons: it is worth investing in a timer regardless of which light you choose. Seedlings are sensitive to photoperiod and inconsistent light cycles stall growth. A basic plug timer costs a few pounds and removes the variable of forgetting to turn lights on or off.
Frequently Asked Questions
How Many Hours of Light Do Seedlings Need Per Day?
Most vegetable and herb seedlings do well on 14 to 16 hours of light per day. Tomatoes, chillies, and herbs will all perform well at 16 hours. Avoid running lights 24 hours — most plants benefit from a dark period, and continuous light can cause physiological stress in some species. A plug timer set to 16 hours on, 8 hours off is the standard starting point.
How Far Should Grow Lights Be Above Seedlings?
This varies by light type. T5 LED strips like the Barrina work best positioned 3 to 6 inches above the seedling canopy — they run cool, so close proximity is fine. Full-spectrum LED panels like the TS600 or SF1000 should hang 24 to 30 inches above seedlings to avoid over-intensity. If seedlings are stretching toward the light, they are not getting enough. If leaves look bleached or curled, the light is too close or too intense. See our guide on how far grow lights should be from plants for a full distance chart.
Can I Use Grow Lights for Both Seedlings and Mature Plants?
Yes, but you need to manage intensity. A panel like the Spider Farmer SF1000 or Mars Hydro TS600 is genuinely dual-purpose: run it dimmed and high for seedlings, then lower and brighter as plants mature. T5 strip lights are excellent for seedlings and early vegetative growth but tend to lack the output and canopy penetration for flowering plants. If you want one light to take plants from seed to harvest, a dimmable quantum board panel is the right choice.
What Spectrum Is Best for Seedlings?
Seedlings respond best to a cooler, blue-weighted spectrum in the 5000K to 6500K colour temperature range. This promotes compact, stocky growth with tight internode spacing. Red-heavy spectrums in the 2700K to 3000K range encourage stretching and are better suited to flowering. Most full-spectrum grow lights include both, which is why a cooler white LED with some red added works well across the seedling and early vegetative stages.