Window light vs grow light for seedlings

The sources disagree. Cornell Extension recommends a sunny windowsill, and Oklahoma State says most windows provide too little light.

What the sources say

Cornell Monroe: a sunny windowsill is recommended for seedlings.
Oklahoma State: most windows provide too little light, and tinted windows block more. Insufficient light causes leggy, weak plants.
Utah State: poor light is the most common cause of tall, thin seedlings, and the fix is supplemental light close to the plants.
Iowa State: grow lights are often not necessary, and a plug-in shop fixture is a good choice for most home gardeners.

If seedlings lean toward the window or stretch, the light is not enough. Add a fixture. See leggy seedlings.
If you have no sunny window, or the window is tinted, use a shelf with lights. See how to set up a shelf.
If you use a window, Utah State says to rotate plants 180 degrees regularly when light comes from one direction.
Windows do not give you control of the hours. A timer on a shelf light does. See hours per day.

Sources checked 2026-10-14. Pages on this site are researched, not hands-on tested.