The Best Grow Lights for Seedlings (2026): 7 Picks by Setup

The best grow light for seedlings, for most people, is a set of plain 2 ft LED strips hung under a wire shelf: the Barrina T5 2ft 5000K Grow Lights (4 pack). Each strip is 10 watts, 5000K white, with a 120 degree beam, and up to 16 link on one chain. Hang them 2 to 4 inches above the seedlings, run them 16 hours a day on a timer, and raise them as the plants grow. Shifting Roots puts the priority plainly: keeping seedlings at the correct distance from the light, and watering them right, is "way more critical than buying the best-quality grow light".

What no grow light listing tells you is how many you need, so this guide works it out. For every pick we take the maker's own figures (length, beam angle, coverage, how many link together), lay them over a standard 1020 seed flat, and count the lights a 2-flat, 4-flat and 4-shelf setup needs. The other questions people ask (how far, how long, how strong) have clear answers from university extension services, and we give each one once, in plain numbers.

One note on who is writing: we make digging spades, not lights, so nothing on this list is ours and nothing here was grown under our own lamps. How we picked is below.

Disclosure: some links in this guide are affiliate links to Amazon. As an Amazon Associate, Spear Head Spade earns from qualifying purchases. This is at no extra cost to you, and it never changes our honest, use-based recommendations.

The best grow lights for seedlings at a glance

How we chose these

We did not grow seedlings under any of these lights. We compared each maker's specifications (from the brand's own site where it has one, and the Amazon listing where it does not) against what named testers reported: Wirecutter's shop light piece, Shifting Roots, Savvy Gardening, The Spruce, Southern Living and Popular Mechanics. We read Wirecutter, The Spruce and Southern Living in archived 2025 copies. The growing science (distance, hours, light strength) comes only from the University of Minnesota Extension, Clemson Cooperative Extension and University of Illinois Extension.

One rule decides the first pick. Nobody tested this exact pack. The Spruce put a 3 ft full spectrum Barrina T5 8 pack under other options it tested, and Shifting Roots links Barrina's 2 ft full spectrum strips; we list the 5000K 2 ft 4 pack from the same Barrina T5 line, because 2 ft matches a 1020 flat and four strips light two flats at the closest height. Where no tester named our exact model we say so in that pick. Award labels below are from the 2025 copies we read; Southern Living's current page makes the Soltech Grove its Best Overall.

The best grow lights for seedlings, by setup

1. Barrina T5 2ft 5000K Grow Lights (4 pack): the best grow light for a shelf of seed trays

The Barrina T5 2ft 5000K Grow Lights (ASIN B0DJ12Z9BB, Barrina model MF10) are the LED version of what the extension services describe, tubes of light a few inches over each flat; here they are cable tied under a wire shelf. Barrina's own page gives 10 W per light, 5000K, a 120 degree beam and up to 16 lamps linked in series, and its Amazon detail page gives each strip as 23.6 in long, which is the number that makes it fit: a standard 1020 flat is 21.06 in long, so one strip covers one flat end to end with a little spare.

The 120 degree beam is what lets us count them. Hung 2 in up, the height the University of Minnesota calls ideal, a strip lights a band about 6.9 in wide, so a flat's 10.81 in width takes two strips, and this 4 pack runs two flats. Treat two as the floor: Kristen Raney at Shifting Roots, who hung Barrina strips under wire shelves, writes "I needed three rows of lights for each shelf", and the wire rack she links is listed today with shelves 13.4 in deep, about one flat wide. Each strip has its own on and off switch, and the box has two power cords, three connecting cords (20 in long on Barrina's page, where the Amazon listing says 39.37 in; we use Barrina's), clips, double sided tape and cable ties.

Mount them with the clips and cable ties, not the tape. Shifting Roots warns against strips fixed with stick-on adhesive because "you'll have no flexibility with raising and lowering and might end up with leggy seedlings", and she made her own Barrina strips adjustable by wiring them to the shelf. Barrina itself says the strips are non-magnetic and not for rough or dusty surfaces. Raney links Barrina's 2 ft full spectrum strips and says "they are super easy to put together"; The Spruce tested the 3 ft 8 pack and called it "an excellent option" for a basement or a space set aside for plants.

Where it loses: no timer and no dimmer. The Spruce found "the lights are not dimmable" and that "the lights provide no heat", which mattered in a cold basement. Shifting Roots is blunt that "they are not the highest quality". And at two or three strips a flat, one 4 pack covers two flats or fewer, so a shelf of four flats means two or three packs.

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2. TaiGLow 4ft LED Shop Light (2 pack): the best shop light for seedlings

The TaiGLow 4ft LED Shop Light (ASIN B0GJ5K1SGG) is here because of a rule, not a review. Wirecutter's writer grew his seedlings under garage shop lights, and the rule he reports from the garden author Gary Pilarchik is that white LED shop lights "with a brightness of 5,000 lumens or higher and a color temperature of 5,000 K or higher" can be used as grow lights for seedlings. Both of Wirecutter's own shop lights are sold at Walmart and Harbor Freight, not Amazon. This one clears both halves of the rule on its listing: 7000 lm at 6500K, from 50 W.

It also has the two features Wirecutter's writer praises in his own lights. It comes with hanging chains, which Wirecutter calls the easy way to raise the light as seedlings grow, and it is linkable: TaiGLow says up to 7 link end to end from one outlet, while recommending no more than 5 in a series. Each fixture is 48 in by 2.36 in, has a pre-attached power cord with a plug, is ETL listed, and the listing states a 3 year warranty. A 48 in light spans two flats laid end to end, so one light covers two flats and a pair covers four.

No tester named this model, and we will not pretend one did. It is on the list because it is an Amazon shop light that passes the number Wirecutter's source gave.

Where it loses: TaiGLow publishes no beam angle, so our count below assumes one light over each row of flats laid end to end, which is a floor, not a promise. And Wirecutter's own complaint about shop lights applies here too: they are "kind of ugly and can radiate an unpleasant amount of light, especially at night". This is a garage fixture in your spare room.

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3. iGrowtek 2ft Grow Light Stand: the best for one tray on a table

The iGrowtek 2ft Grow Light Stand (ASIN B07ZR6XSQK) is the only light that two of the testers we read both named Best for Seedlings: The Spruce and Southern Living each grew seeds under it. It is a single T5 LED fixture with a wide reflector on an iron frame; the Amazon detail page gives 10 W, 900 lumens, 4000K, and a stand 27.2 in long and 19.7 in high. Set it on a table and put the tray under it.

The Spruce put it together "in under five minutes" and says at 2 ft long it "fits a larger seeding tray or a few plants". Southern Living grew tomatoes, spinach and basil under it against a window control group: the tomatoes and spinach "both grew noticeably larger under the grow light", and the plants "grew much better under it than the Leoter model". The light hangs on adjustable straps, so you lower it to the seedlings and raise it as they grow.

Where it loses: it runs out of height. The Spruce found "the light can only be as high as 6 to 7 inches", so taller transplants move on. Southern Living's basil "grew to the same size as the control group", and it lists "Light isn't adjustable" (the height is, by its own account) and "Setup requires two people" as its cons. At 4000K it sits under Pilarchik's 5,000 K line for shop lights, though Wirecutter's own writer got "healthy starts" under a 4,000 K shop light. At 10 W per flat it puts the least power per flat into our sizing table. And it has no timer of its own (The Spruce: "the light doesn't come with any other features, like a timer or dimmer"), so pair it with pick 7.

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4. Barrina CX3 4-Tier Plant Stand: the best all-in-one seed starting shelf

The Barrina CX3 4-Tier Plant Stand (ASIN B0C76VJ1J6) is the answer if you want to buy the shelf, the lights and the timer at once. Its listing gives a stand 35.4 in by 13.8 in by 70.9 in tall with four wire tiers, each rated to 90 lb, three 36 W T5 LED lights 35.4 in long, a mechanical timer, and a waterproof PP pad for each layer, with no tools needed to build it. Its Amazon detail page lists the lights as 5000K and the stand as on wheels. Savvy Gardening's Niki Jabbour recommends it and notes that it "comes with three strips of T5 LED grow lights and a timer to turn the lights on and off daily".

Do the tray arithmetic before you buy it. A 1020 flat is 21.06 in by 10.81 in. On a 35.4 in by 13.8 in shelf one flat fits lengthwise, two end to end need 42.12 in, and two side by side need 21.62 in of depth. So each tier holds one flat, and with three lights for four tiers, at most three tiers have a light over them. This is a three-flat seed starter, not a four- or eight-flat one.

Where it loses: exactly that capacity. Three lit flats is fewer than the four that two TaiGLow shop lights cover in our sizing table. Savvy Gardening lists no drawbacks, and it is the only tester we found for this model, so the tray count above is ours, not theirs.

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5. Mars Hydro TS1000: the best panel for many trays or a grow tent

The Mars Hydro TS1000 (ASIN B07RSRX1RS) is one flat panel instead of a row of strips. Mars Hydro's page gives 150 W, a core coverage of 2 ft by 2 ft and a maximum of 2.5 ft by 2.5 ft, a PPF of 343 umol/s, a 0 to 100 percent dimmer on the external driver, and a panel 15.98 in by 12.83 in by 1.9 in. It is the only pick whose maker publishes a seedling setting: in an answer about a 2 x 2 ft grow tent, 12 in above the plants at 50 percent. The Spruce's 2025 version named it Best Large Capacity, dimmed it so "it wasn't too distracting", and says it "did effectively grow our seedlings during testing".

Take that setting seriously, with the maker's own caveat that "these are not absolute values and may need to be adjusted". Southern Living's result with the smaller Mars Hydro, below, shows what a panel like this may do to seedlings. For context only: 343 umol/s spread over the 2 ft by 2 ft core, if all of it lands on that square, averages about 923 umol per square meter per second at full power, and about 460 at half if output falls with the dimmer. The University of Minnesota's highest band for indoor plant light, the one it gives for south- or southwest-facing windows, is 250 to 450; it gives no ceiling for seedlings. Two flats side by side fit inside the core area, so one panel runs two flats and two panels run four.

Where it loses: it is too much light if you ignore the dimmer. Southern Living tried the 100 W Mars Hydro, a smaller sibling, and its "100-watt bulb seemed to burn the leaves of our seedlings and didn't improve growth overall". The Spruce lists "No built-in timer" and "Fixture doesn't blend in well in small spaces". Mars Hydro's page says up to 30 can be daisy chained for dimming where the Amazon listing says 50 with a connector bought separately; we use Mars Hydro's figure.

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6. Leoter 4-Head Clip Grow Light: the best top-up for a windowsill tray

The Leoter 4-Head Clip Grow Light (ASIN B082YWKWGH) is for the grower with a tray on a sill and no room for a shelf. Its listing gives 80 LEDs (32 red, 12 blue, 20 yellow, 16 white) on four heads with 360 degree goosenecks, a metal clamp, three spectrum modes, 10 brightness levels and a timer that runs 3, 9 or 12 hours. The Spruce's 2025 version named it Best Adjustable-Spectrum and found it "very easy to clip onto our bookshelf"; Southern Living named it Best Clip-On.

Read Southern Living's result before you buy it as your only light, though. Growing basil, tomatoes and spinach against a window control, its testers reported "we didn't see a beneficial difference between plants grown under the light and our control group", and concluded that it "could add an extra boost of light for plants near low-light windows". That is the job we list it for: topping up daylight, not replacing it.

Where it loses: its own timer tops out at 12 hours, short of the 16 seedlings want, and the listing says the timer "needs to be reset if the grow light is powered off", so it will not pair neatly with a plug-in timer. The Spruce wished the timer stayed on longer and notes it has no stand. We also leave its wattage out: the detail page lists 80 watts on a 5 volt USB supply, which would be 16 amps through a USB plug, and we do not trust that figure.

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7. BN-LINK 24-Hour Mechanical Timer (2 pack): the timer to add

The BN-LINK 24-Hour Mechanical Timer (ASIN B01LPSGBZS) earns its place because most of the lights above have no timer of their own. All three extension services we cite put a timer in the setup, and a pin timer does that job without an app. The listing gives up to 24 on and off settings a day in 30 minute steps, pins down for on and up for off, a 3-prong plug, two timers in the pack, and says it is compatible with LED bulbs. Both The Spruce and Popular Mechanics link this exact timer as the one to add to a light without one.

The listing rates it "125-Volt, 60 Hz./15-Amp, 1875-Watt resistive/8-Amp, 1000-Watt tungsten/5 Amp ballast". Check your lights' combined wattage against those ratings, and each light's manual, before you put several on one timer.

Where it loses: it is a dial with pins, so the schedule is set by hand and changed by hand. If you want to set the schedule from a phone, see the Kasa plug under Also considered.

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Also considered: models that missed the list and why

Barrina 4ft T8 Grow Light (6 pack). Popular Mechanics lists it, chosen by research rather than a test, and it is made for a 4 ft shelf: six 42 W, 4 ft lights that link up to 6 in a series, with reflectors. It missed because 2 ft strips match a single flat and the 4 pack above covers the same shelf job in smaller steps, and because Popular Mechanics' own cons are "Non-dimmable", "Narrow lights" and "Reflectors aren't fixed".

Soltech Grove LED Grow Light Bar. The most named single model we read: Popular Mechanics' Best Overall, Best Mounted in the 2025 versions of The Spruce and Southern Living, and Best Overall on Southern Living's current page. Southern Living's result is strong: seedlings under it "sprouted several days before those in natural light", and "all of our plants grown with the light were double or almost double the size of those in the control group". It missed on shape: Soltech's listing gives 18 in long and 11 watts in warm white 3000K, so one bar is 3.06 in shorter than a 1020 flat, and its listing pitches it for shelves, cabinets and herbs rather than rows of trays. Southern Living also found the 6 ft cord short and the adhesive weak.

LBW Grow Light with Stand. The Spruce's Best Overall, a gooseneck head on a tripod that extends from 15 to 48 inches, with a 30 W draw on its listing. It missed because it lights a spot rather than a flat, and because Southern Living, testing an LBW with a taller stand, found "there wasn't a significant difference between plants grown under this light versus the control group".

Kasa Smart Plug Mini EP25 (4 pack). Wirecutter's top smart plug, and the one its seedling writer suggests adding "to give your plant babies a bedtime". It monitors energy use and runs from the Kasa app or a voice assistant, with a 15 A, 1800 W maximum. It missed only because it needs Wi-Fi and an app to do the one thing the pin timer does on its own.

hykolity 4ft Linkable LED Shop Light. The same shape as pick 2, with hanging chains, links up to 6, 42 W and 5000K. It missed on one number: 4400 lumens, under the 5,000 in Pilarchik's rule. Wirecutter does report a grower doing well at 4,000 lumens, so it is not wrong, just short of the rule we used.

Ohuhu Indoor Greenhouse with Grow Light. Our mini greenhouse guide picks this as the best for starting seeds indoors: its four shelves "perfectly fit 10" × 20" seed trays", with a full spectrum light, a 4, 8 or 12 hour timer and brightness from 10 to 100 percent. Its built in timer stops at 12 hours, short of the 16 below, and its listing does not say whether the light comes back on by itself when power returns, so check that before you rely on an outlet timer. It is a greenhouse that brings its own light rather than a light, and its listing publishes no wattage, so it has no row in the light tables below.

Sansi 24W Grow Light Bulb. Southern Living's Best Bulb, and the top growth result in Southern Living's test: it "produced the most noticeable plant growth of all the models we tested, doubling the size of two plants and tripling the size of one plant versus the control groups". Its listing gives 24 W, 4000K and a PPF of 36.2 umol/s, with a PPFD of 177.06 at 1 ft. It missed because a bulb goes in a lamp you supply and lights a spot, not a flat, and Southern Living's own con is that the "Instructions don't mention how far to place bulb from plants".

How many grow lights do you need for seedlings?

Start with what the makers actually publish, which is less than you would think.

Two columns are missing because almost nobody fills them. Only Barrina publishes a beam angle for these lights, 120 degrees for the T5 strips; Mars Hydro's listing gives a "refraction angle of 120°" for its reflector, which is not the same thing, and we do not use it. Only Mars Hydro gives a seedling hanging height, in the tent answer quoted in pick 5.

Now the count. The table below is computed by us from those figures and one published tray size, Bootstrap Farmer's standard 1020 flat at 21.06 in by 10.81 in. The setups are 2 flats, 4 flats, and a 4-shelf rack holding two flats per shelf. The rules:

• Layout. Under 4 ft lights the flats go end to end, two to a 42.12 in run, with one run per light. Under 2 ft strips and the panel they go side by side, 21.06 in by 21.62 in for two.
• Strips. At 2 in up, the height Minnesota calls ideal, a 120 degree strip lights a band 2 x 2 x tan(60 degrees), about 6.9 in wide, so each flat takes two strips. That is a floor, not a promise: Shifting Roots needed three rows of strips on a shelf about one flat wide, and the table gives that count too.
• Lights with no published beam angle get one light over each run of flats. That is a minimum, and the row says so.
• Stands and panels use their own stated size or coverage.

How to read it. A 4 pack of the Barrina strips runs two flats at two strips a flat, and one flat at three. A full rack at two per flat is 16 strips, Barrina's stated limit for one series; at three per flat it is 24, more than one series. The 4 ft rows need shelves at least 42.12 in long for two flats end to end. For the TS1000, each shelf needs room for the 12 in hanging height plus the 1.9 in panel, about 13.9 in above the seedlings before they grow. The Leoter, the LBW and the Sansi bulb have no row because none of them publishes a coverage, and the timer has no row because it lights nothing.

How far should grow lights be from seedlings?

For strips, tubes and shop lights, 2 to 4 inches above the tops of the seedlings, raised as they grow. The University of Minnesota's seed starting page says "Keep lights no more than 4 inches above the tops of your seedlings: as close as 2 inches is ideal. Lack of light is the major cause of elongated, skinny stems." Clemson gives the same 2 to 4 inch gap for 48 inch fluorescent tubes. Minnesota's separate lighting page gives 4 to 6 inches for seedlings, so 4 in is where the two pages meet; start close and raise the lights as the plants grow.

A high output panel is the exception: follow its maker. Mars Hydro's answer for the TS1000 in a 2 x 2 ft tent is 12 in at 50 percent power for seedlings, values it says "are not absolute". It is a 150 W light, and Southern Living, testing the smaller 100 W Mars Hydro, found it "seemed to burn the leaves of our seedlings".

Be careful with the bigger numbers you will see elsewhere. The Spruce's placement section gives 12 to 18 inches for LED and fluorescent lights in general, and Barrina's own blog says 12 to 24 inches for seedlings under LED grow lights. For a 120 degree strip the geometry answers that: at 12 in up its light spreads over a band about 41.6 in wide, six times the band at 2 in and nearly four flats across, from 10 W. For strips, the extension figure is the one to use.

How many hours should seedlings be under a grow light?

Sixteen hours a day, on a timer, with the lights off at night. Sixteen sits inside every seedling range we found: the University of Minnesota's lighting page gives 16 to 18 hours for seedlings, Clemson says transplants "need 16-18 hours of bright light (natural and artificial)", Illinois Extension runs 16 hours "with 18 hours being the maximum for seedlings", and Minnesota's seed starting page gives 12 to 16. None of them recommend leaving the lights on around the clock, and Minnesota says so outright: "Don't leave the lights on continuously, as many plants need some dark period each night to develop properly." Wirecutter's horticulture therapist says the same: "You don't want to leave lights on them 24 hours a day."

That is why the timer is a pick. Of our six lights, only the Barrina CX3 and the Leoter come with timers, and the Leoter's stops at 12 hours.

How strong should grow lights be for seedlings?

Stronger than a window, and measured in the right unit. The University of Minnesota puts indoor light into three bands by PPF: low (50 to 150 umol per square meter per second), medium (150 to 250) and high (250 to 450), and says flatly that "Low lighting is not sufficient for starting seeds indoors". It also warns that lumens "are less relevant when considering lighting for plants", because they measure brightness to the human eye. The trouble is that only two makers on this page publish a PPF figure at all: Mars Hydro, and Sansi for the bulb under Also considered, which lists a PPF of 36.2 umol/s and a PPFD of 177.06 at 1 ft.

So for everything else you work with what the listing gives. For white shop lights, Wirecutter's rule from Gary Pilarchik is 5,000 lumens and 5,000 K or more, which our shop light pick meets. For strips, the practical strength control is distance, which is why the extension services put the light so close (see the band widths above). For a panel, it is the dimmer.

One rule of thumb we did not use. The Spruce says "you need 32 watts per square foot", and Southern Living says most experts put it at 32 to 40. A flat is 1.58 sq ft, so the Barrina strips at two per flat work out near 12.7 W per sq ft and the TaiGLow near 15.8, and only the TS1000 at full power, near 47, clears 32; Mars Hydro's own seedling answer runs it at half power. A watts rule like that does not fit LED strips hung inches above seedlings, so we size by coverage and height instead.

Should I use grow lights on seedlings?

Yes, if you start seeds indoors in late winter. The University of Minnesota: "It's much better to grow seedlings under fluorescent or LED lights than to rely solely on natural light, even in a greenhouse." Clemson describes what happens without enough light: "Under low light conditions, vegetable seedlings become leggy, weak, and tend to topple over when they are a few inches tall." The Spruce quotes Iowa State University's Aaron Steil: "almost universally, we don't have enough light even in the brightest windows to produce robust stocky plants."

Minnesota's lighting page adds the useful exception: in a bright south or southwest window "You may be able to start seeds without artificial lighting, but seeds that need more time indoors, such as tomatoes and peppers, may become leggy without extra light." Tomatoes and peppers are the long-indoor seeds Minnesota names as needing the extra light.

What color light is best, and worst, for seedlings?

White, or a balanced mix. The University of Minnesota says "Blue light or mixed light bulbs are suitable for starting seeds and leafy greens" and "White lights or mixed/balanced light bulbs are suitable for most plants at any stage of growth". Wirecutter quotes the same extension: "Typically, plants use more blue and blue-green light when they are seedlings, and more red light later on in their life cycles". That is why every strip, shop light and stand we picked is white light, 4000K to 6500K.

The worst light for seedlings is an ordinary incandescent bulb. Minnesota lists "High far red light causes plants to stretch" among its cons, and Illinois Extension says incandescent bulbs "get too hot for seedlings". Stretching is the exact problem a grow light is there to stop.

Strip, shop light, stand or panel: how to choose

• You have a wire shelf and more than one flat: LED strips (pick 1) or shop lights (pick 2) under each shelf, on chains or cable ties so they move.
• You have one flat and a table: the iGrowtek stand (pick 3), and plan to move tomatoes on once they pass its 6 to 7 inch ceiling.
• You want it all in one box: the CX3 (pick 4), knowing it lights three flats.
• You have a tent, or four flats and a high ceiling: the TS1000 (pick 5), dimmed.
• You have a sunny sill and a few pots: the Leoter (pick 6) as a top-up to daylight.
• Whatever you pick: a timer (pick 7) unless the light has one that reaches 16 hours.

After the lights: hardening off and planting out

Seedlings raised under lights have never met sun or wind. Minnesota warns that without "hardening off," their leaves may be scorched by sun or wind, and says to start "by putting them outside for a few hours in the shade during the warmth of the afternoon, protected from wind". Clemson starts that once plants are around three inches tall. Minnesota adds that "An easy way to harden off plants is to place them in a coldframe, a temporary mini-greenhouse", which is what our mini greenhouse and cold frame guide covers, and our frost protection guide is there for the late cold night after they go out.

Then they go into the ground. If that ground is a new bed, our raised garden bed guide covers the build and our soil test kit guide covers testing what is in it. For the planting itself, the Spear Head Spade Mini is our 30 inch precision spade, made for close transplanting in raised beds and containers. And if you are shopping for someone who grows indoors all year, our gifts for plant lovers list is the place to look.

Common questions

What is the best grow light for seedlings?

For most people, LED strips under a wire shelf: the Barrina T5 2ft 5000K 4 pack. Each 2 ft strip spans a standard 1020 flat; plan on at least two strips per flat, hung 2 in up, so the pack runs two flats, and Shifting Roots needed three rows of strips per shelf. For one flat on a table, the iGrowtek stand, which The Spruce and Southern Living both named best for seedlings.

How far should grow lights be from seedlings?

2 to 4 inches above the seedling tops for LED strips, tubes and shop lights, raised as they grow. The University of Minnesota says no more than 4 inches, with 2 ideal, and Clemson gives the same 2 to 4 inch gap. A high output panel is the exception: Mars Hydro's answer for the TS1000 in a 2 x 2 ft tent is 12 in at 50 percent power for seedlings, values it says are not absolute.

How many hours should seedlings be under a grow light?

16 hours a day, on a timer, with a dark period every night. Minnesota gives 16 to 18 hours for seedlings on one page and 12 to 16 on another, Clemson 16 to 18, and Illinois Extension 16 with 18 as the maximum. None of them recommend leaving the lights on 24 hours.

Can I use a regular LED shop light as a grow light for seedlings?

Yes. Wirecutter's writer grew seedlings under garage shop lights for three seasons, and the rule he reports is white LED at 5,000 lumens or higher and 5,000 K or higher. Our shop light pick, the TaiGLow 4ft, lists 7000 lumens at 6500K. Hang it on its chains 2 to 4 inches above the seedlings, the same as any strip.

How many grow lights do I need for a seed tray?

For 2 ft LED strips, at least two per 1020 flat, hung 2 in up; Shifting Roots, who hung Barrina strips, needed three rows per shelf. For a 4 ft shop light, at least one light over each pair of flats laid end to end, since a 48 in light spans two flats. A 2 x 2 ft panel like the TS1000 covers two flats side by side.

Do seedlings need grow lights if they are in a sunny window?

Usually, yes. The University of Minnesota says it is much better to grow seedlings under fluorescent or LED lights than on natural light alone, and that in even a bright window, tomatoes and peppers may become leggy without extra light. A clip light like the Leoter can top up a sunny sill, but Southern Living found it no better than the window on its own.