Starting seeds indoors is one of the best ways to get a jump on the growing season—but you need the right light. After more than 30 years of starting seeds under lights in Sonoma Valley, I’ve learned that most seedling problems—stretching, legginess, slow growth—come down to insufficient or poorly placed lighting.

The good news: you don’t need expensive equipment. A simple, reliable light setup placed at the correct distance can produce strong, compact, garden-ready starts every time.

This guide covers the best types of lights for starting seeds and exactly how to use them.

Table of Contents

Best Types of Lights for Starting Seeds Indoors

1. LED Shop Lights (Best Overall Value)

LED shop lights—especially full-spectrum or 4000–5000K daylight LEDs—are my go-to choice.

Why they work well:

Inexpensive
Energy-efficient
Produce little heat
Provide bright, even light seedlings respond to
Widely available

What to look for:

4000–5000 Kelvin (daylight range)
Minimum 4,000–5,000 lumens per fixture
Full-spectrum or “daylight” labeled LEDs
Linkable fixtures if you’re expanding your setup

My experience:

Most of my indoor starts—tomatoes, peppers, brassicas, lettuces, herbs—grow under LED shop lights hung 3–4 inches above the seedlings.

2. T5 Fluorescent Grow Lights (Reliable Classic Choice)

T5 fluorescents were the gold standard for years and still work beautifully.

Pros:

Excellent light distribution
Cool operation
Perfect for metal shelving setups

Cons:

Bulbs need replacing every 1–2 years
Use more energy than LEDs

These lights are ideal for growers who already own them—I still have two old T5 fixtures that perform perfectly.

3. Full-Spectrum LED Grow Lights (High-Performance Option)

These have dedicated diodes designed to mimic natural sunlight.

Best for:

Warm-season crops requiring strong early growth (peppers, tomatoes, eggplants)
Gardeners wanting maximum efficiency with minimal heat

Why choose them:

Long lifespan
Highly efficient
Excellent for compact growth

A high-quality LED grow light can produce very dense seedlings in a small indoor space.

4. Avoid These Lights

Incandescent bulbs

Too hot, wrong spectrum, too dim. They cause stretching and burns.

Standard desk lamps or room lighting

Not nearly bright enough for seedlings. Plants stretch toward any weak light source.

How to Use Indoor Lights to Start Seeds Successfully

Using the right light is one part of the equation. The other part—just as important—is distance, duration, and movement of the lights. Most legginess is caused not by weak lights but by lights placed too far above seedlings.

Correct Light Placement

1. Distance from Seedlings

Seedlings need bright, consistent overhead light—not ambient room light.

General placement rules:

LED shop lights: 2–4 inches above the seedling tops
T5 fluorescents: 2–3 inches
High-output LED grow lights: 6–10 inches

Adjust as they grow:

Raise the lights gradually so they stay just above the foliage.

My Sonoma Valley experience:

I lower lights early—even to 1–2 inches above germinated seedlings—especially for broccoli, kale, lettuces, onions, and herbs, which stretch quickly without strong light.

2. Duration (How Many Hours Per Day?)

Seedlings need 14–16 hours of bright light per day.

Use a timer:

A $10 plug-in timer is one of the best seed-starting tools you can buy.
I set mine to 6 AM–10 PM throughout the season.

3. Even Light Distribution

Make sure each tray receives the same intensity:

Hang lights parallel to the tray
Keep trays centered under the light spread
Avoid shadows from shelving or hanging chains

If one side of the tray leans toward the light, rotate trays every 2–3 days.

4. Light Color (Kelvin Rating)

For seed starting, you want “daylight” color temperature:

4000K–5000K: Best for germination and early growth
5000K–6500K: Best for compact growth

Anything labeled “warm white” produces too much yellow light and can cause stretching.

5. Heat From Lights

Modern LEDs produce very little heat—good for seedlings. Fluorescents produce mild warmth, useful in cooler rooms.

If you’re using heat mats:

Keep lights close
Let heat mats warm only the root zone
Turn off heat mats once seedlings emerge

This combination prevents legginess while encouraging deep root development.

How to Prevent Leggy Seedlings with Indoor Lights

Here are the practices that have given me consistently compact, thick-stemmed seedlings for decades:

✔ Keep lights 2–3 inches above seedlings

Most legginess happens when lights are 6–12 inches too high.

✔ Provide enough daily light (14–16 hours)

Short days produce weak stems.

✔ Strengthen stems with airflow

A small fan on low—15–20 minutes a day—mimics outdoor breezes.

✔ Avoid warm, dark rooms

Seedlings stretch quickly when warm but underlit.

✔ Bottom-water to keep the surface dry

Wet surfaces + low airflow = damping-off risk.

✔ Move seedlings to brighter light as soon as they germinate

Don’t wait until true leaves appear.

✔ When in doubt, add another fixture

Two LED shop lights can cover three trays and prevent shadows.

Final Thoughts

Starting seeds indoors becomes much easier when you have the right lights in the right place. With strong overhead light, proper distance, and consistent scheduling, seedlings stay short, sturdy, and ready for transplant. After 30+ years of seed starting—indoors under lights and outdoors in Sonoma’s mild climate—the biggest lesson is this: light is the foundation of strong seedlings. Get the lighting right, and everything else becomes simple.