Step 3 - Seed Starting
The Best Grow Lights for Seedlings
The single highest-value purchase in seed starting. A windowsill grows stretched seedlings; a strip light three inches above them does not.
Janet H. - the hands-on owner behind Janet Media Group.
Published - last updated
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Hang a full-spectrum LED strip 2 to 4 inches above the seedlings and run it 14 to 16 hours a day. That is the whole answer. Distance matters far more than wattage, and no light at 18 inches does what a modest one does at three.
Quick picks
| # | Product | Best for | Score | Price |
|---|---|---|---|---|
| 1 |  Top pickBarrina T5 Full-Spectrum LED Grow LightsLinkable LED strips, full spectrum | Stopping leggy seedlings | 9.0 | Check price on Amazon |
| 2 |  Burpee Self-Watering Seed Starting KitCell tray, dome and watering mat in one box | First-time seed starting | 8.4 | Check price on Amazon |
| 3 |  Bootstrap Farmer 1020 Seed TraysHeavy-gauge 1020 trays, reusable for years | Trays that last more than one season | 8.5 | Check price on Amazon |
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Scores are our own editorial judgment, formed from published specifications and independent sources. They are not aggregated customer ratings, and they are not the result of hands-on testing, which we do not currently do. See how we choose.
Why seedlings stretch
A seedling grows toward light. When light is weak or comes from one side, the plant invests in stem length trying to reach it -- gardeners call the result leggy, and extension guidance identifies insufficient light as the most common cause.
A late-winter windowsill is exactly that situation: short days, low sun angle, glass cutting the intensity, and light arriving from one direction only. Turning the tray daily helps a little and does not solve it.
| South-facing windowsill | LED strip 3 in above | |
|---|---|---|
| Light direction | One side only | Directly overhead |
| Hours available | Whatever the day gives | 14 to 16, set by a timer |
| Intensity at the leaf | Low in late winter | High, because it is close |
| Typical result | Pale, stretched, floppy stems | Short, stocky, dark green |
What to look for
- Full spectrum, around 5000K white. Blue-weighted or balanced white light suits seedlings and leafy growth. The purple-only fixtures are aimed at flowering and are unpleasant to live with.
- Linkable strips. Daisy-chaining several strips from one outlet is what makes a whole shelving rack practical.
- Low heat. LEDs run cool enough to sit inches from the leaves, which is the entire point. Older fluorescent tubes needed more clearance.
- A timer. Consistency matters more than exact duration, and a timer removes the decision.
- Adjustable height. The light has to rise as the plants do, whether that is chains, a rack shelf or a hanging kit.
How long to run them
Fourteen to sixteen hours a day is the usual recommendation for seedlings. Plants also need a dark period -- running lights 24 hours does not produce better growth and in some crops causes problems.
Raise the light as the seedlings grow to keep that 2 to 4 inch gap. If they start stretching again, the light has got too far away.
What a light does not fix
Warm nights also cause stretching -- extension guidance notes that night temperatures above roughly 60 to 65F encourage leggy growth. If your seedlings are stretching under good light, look at the temperature, and at crowding: seedlings competing with each other in a packed cell stretch just as they would in poor light.
Bottom heat is a separate tool for a separate job -- see seedling heat mats. It speeds germination and should come off afterwards, because heat after germination makes stretching worse.
The picks in full
Top pick
Barrina T5 Full-Spectrum LED Grow Lights
Barrina
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The fix for the most common seed-starting failure. A windowsill grows pale, stretched seedlings; a strip light 3 inches above them does not.
A seedling stretches toward light. On a windowsill in February the light comes from one side and there is not enough of it, so the stem elongates, the plant gets pale and floppy, and it never fully recovers. That is the single most common seed-starting failure and it is entirely a light problem.
LED strips fix it because they can sit 2 to 4 inches above the leaves without cooking them. Distance is what matters more than wattage: the same light at 18 inches does very little.
Run them about 14 to 16 hours a day on a timer and raise them as the seedlings grow. Linkable strips mean a whole shelving rack runs from one outlet.
What works
- Directly fixes stretched, leggy seedlings
- Linkable, so one outlet runs a whole shelf
- Very low heat, so it can sit close to the leaves
- Cheap to run
What does not
- Needs to be within a few inches of the seedlings to work
- Height must be adjusted as plants grow
- White light is unflattering in a living space
Skip it if: you have a genuinely bright greenhouse and are sowing in season. Then you are buying light you already have.
| Type | Linkable LED strip lights |
|---|---|
| Spectrum | Full spectrum, commonly 5000K white |
| Lengths | 1 ft, 2 ft and 4 ft strips |
| Mounting | Clips, hanging kit or double-sided tape |
| Linking | Strips daisy-chain from one outlet |
First-time seed starting
Burpee Self-Watering Seed Starting Kit
Burpee
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Everything in one box with a capillary mat underneath, which removes the single most common beginner failure: uneven watering.
Seeds fail for two reasons in a beginner's first tray: they dried out, or they were drowned. A capillary mat drawing water from a reservoir underneath removes both, because the medium takes what it needs and no more.
The dome is the other useful piece. It holds humidity during germination, which matters most for small seeds sown shallowly.
Take the dome off as soon as the first seedlings are up. Left on, it holds the still, damp air that damping-off fungus needs, and a tray can collapse overnight.
What works
- Capillary watering keeps moisture even without daily attention
- Humidity dome improves germination rates
- Nothing else to buy to get started
- Reusable for several seasons
What does not
- Cells are small, so seedlings need potting on quickly
- Kit price is high relative to buying components
- Dome must come off promptly once seeds germinate
Skip it if: you already have trays. Refill pellets and a dome cost a fraction of a new kit.
| Type | Self-watering seed starting kit |
|---|---|
| Cells | Sold in several counts, commonly 36 and 72 |
| Watering | Capillary mat and reservoir |
| Included | Tray, cells, dome, growing medium |
Trays that last more than one season
Bootstrap Farmer 1020 Seed Trays
Bootstrap Farmer
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Thick enough to pick up full without folding, which is the entire complaint about cheap trays and the reason these cost more.
Anyone who has carried a cheap 1020 tray full of wet compost knows the failure mode: it folds in the middle and the seedlings go on the floor. Heavy-gauge trays do not do that.
The 1020 name is a standard footprint, roughly 10 by 20 inches, and it is worth sticking to. Every humidity dome, heat mat, cell insert and shelf is built around it.
Buy a couple of solid, undrained trays alongside the drained ones. A solid tray underneath lets you water from below, which is gentler on small seedlings than watering from above and keeps the leaves dry.
What works
- Can be lifted full of wet medium without collapsing
- Lasts many seasons rather than one
- Standard 1020 footprint fits every dome and mat
- Solid trays double as reservoirs for bottom watering
What does not
- Several times the price of disposable trays
- Only worth it if you actually reuse them
- Heavier to store in quantity
Skip it if: you start one tray a year. The economics only work once you are reusing them season after season.
| Type | 1020 standard seedling trays |
|---|---|
| Gauge | Heavy-duty, substantially thicker than standard |
| Drainage | Drain-hole and solid versions sold |
| Compatibility | Fits standard domes, mats and inserts |
Common questions
How close should grow lights be to seedlings?
Two to four inches above the leaves for LED strips, and the light needs raising as the plants grow. Distance matters more than wattage -- a modest light three inches away outperforms a powerful one at eighteen, because intensity falls off sharply with distance.
How many hours a day should grow lights be on for seedlings?
Fourteen to sixteen hours, on a timer. Plants need a dark period too, so running lights continuously does not improve growth. Consistency matters more than the exact number, which is why a cheap timer is worth buying alongside the light.
Do I need a special grow light or will any LED do?
A full-spectrum white LED around 5000K is what you want, and ordinary LED shop lights of that description work well. The purple-heavy fixtures are aimed at flowering plants, cost more, and are unpleasant to have in a living space.
Why are my seedlings still leggy under a grow light?
Usually the light is too far away -- check it is within a few inches of the leaves. If it is, look at night temperature, since above roughly 60 to 65F seedlings stretch regardless of light, and at crowding, because seedlings competing in a packed cell stretch as well.
Sources
Factual claims on this page are backed by the published sources below, and product specifications are the manufacturers’ own. Where a figure is not published, we say so rather than estimating it.