A simple LED shop light close to the plants beats an expensive panel hung too high.
Run grow lights 14 to 16 hours daily and give seedlings a true dark period each night.
Raise the light as plants grow, always keeping it close enough that stems stay short and sturdy.
Why a sunny windowsill usually is not enough
Even a bright south-facing windowsill delivers far less light than outdoor sun. Glass filters intensity, windows cool the air around seedlings at night, and plants lean toward the glass producing one-sided growth that is hard to recover from at transplant time.
A simple grow light setup over a shelf or table gives you control over both light quality and duration. That control is what keeps stems short, leaves dark green, and roots building instead of stretching for a distant light source.
- Windowsill light drops off sharply even a few inches from the glass.
- Seedlings under grow lights stay more compact and recover faster after transplant.
- A basic timer makes light consistency effortless.
LED shop lights versus dedicated grow panels
For most home seed starters, a 4-foot full-spectrum LED shop light in the 4000K to 6500K range works well and costs far less than specialty grow panels. Look for lights rated around 2000 to 5000 lumens per fixture. Two fixtures side by side give better coverage than a single narrow strip.
Dedicated grow panels with higher output and adjustable spectrum are worth considering if you start a large number of trays, grow plants beyond the seedling stage indoors, or have a setup where lights are mounted higher than a few inches above the canopy.
- Full-spectrum LED shop lights (4000K-6500K) handle most seedling needs.
- Two parallel fixtures side by side improve coverage and reduce leaning.
- Dedicated panels help when lights must hang higher or when growing to full transplant size indoors.
How close to hang the light and how long to run it
Distance matters more than wattage. Most seedlings need the light source 2 to 4 inches above the leaves. If the light is too far, stems stretch thin and pale. If too close, leaves may bleach or curl from heat stress. Adjust the height a few times per week as seedlings grow.
Run grow lights 14 to 16 hours per day. Plants need a dark period for normal growth, so do not leave lights on around the clock. A simple outlet timer set to 6 a.m. on and 10 p.m. off removes the daily remembering and keeps the rhythm stable.
- Hang lights 2 to 4 inches above seedlings; raise them as plants grow.
- Run 14 to 16 hours per day with a timer for consistency.
- If stems stretch pale and thin, the light is too far or the hours are too short.
When seedlings are ready to leave the grow lights
Seedlings are ready to move on when they have at least two sets of true leaves, stems are sturdy rather than floppy, and the outdoor weather is approaching transplant conditions. At that point, begin hardening off by moving trays outside for increasing periods over 7 to 10 days so stems thicken and leaves adjust to real sun and wind.
Do not move seedlings from grow lights directly into the garden. The transition from steady indoor light to full outdoor sun will burn leaves unless plants are gradually exposed. A few days of increasing outdoor time under dappled or morning sun is all it takes to prepare sturdy transplants for the real garden.
- Transition seedlings outside gradually over 7 to 10 days.
- Start hardening off in dappled or morning sun, not full afternoon exposure.
- Two sets of true leaves and sturdy stems are the minimum before transplanting.
The best grow light is the one hung close enough
Even a modest LED shop light hung 2 to 3 inches above seedlings produces better results than an expensive panel mounted 18 inches high. Distance is the variable that most beginners overlook.
- Check height every few days and adjust as seedlings grow.
- If stems are stretching, the light needs to move closer or run longer.
- A timer is the cheapest upgrade you can make to any light setup.
Quick answers before you head back outside
These are the questions that usually come up once the guide turns into real garden work.
What color temperature is best for seedling grow lights?
For most vegetable seedlings, a full-spectrum LED in the 4000K to 6500K range works well. Cooler light (toward 6500K) encourages compact growth, while warmer spectrum supports flowering later in the plant's life.
Can I use regular LED bulbs instead of grow lights?
Yes, but fixture coverage matters. Standard household LED bulbs in clamp-on fixtures can work for a small number of seedlings if placed very close, but a 4-foot shop light gives far more even coverage for a full tray.
How do I know if my light is too close?
Leaves that bleach pale, curl upward, or develop dry brown edges may be getting too much heat or light intensity. Raise the light an inch and watch for improvement over the next few days.
Should grow lights be on at night?
No. Seedlings need a dark period of at least 6 to 8 hours for normal respiration and growth. Running lights 24 hours a day can stress plants and waste electricity.
