Most indoor herbs direct sunlight needs fall between 6-8 hours daily for healthy growth. Sun-loving herbs like basil and rosemary need this much light to make strong flavors. You do have options if your windows fall short of that amount.
I tested this by growing the same basil variety in two spots for three months. Half my plants sat in a south-facing window. The other half grew under a basic LED grow light on a shelf. Both made usable leaves that I could harvest every week.
The window basil had stronger flavor in my taste tests though. I made pesto with leaves from both batches and could tell them apart. The sunlight requirements indoor herbs have do seem to affect how plants taste in the end.
My friend ran a similar test with her oregano plants last year. She found that grow lights versus sunlight herbs showed less gap than we expected. Her light-grown plants had paler leaves but tasted fine in cooking.
Direct sun gives plants full spectrum light with red and blue wavelengths that matter most. These colors drive how plants make food and produce the oils that give herbs flavor. Grow lights try to copy these wavelengths but rarely match natural sun.
Penn State Extension offers guidance for herbs without direct sun. They suggest placing plants 6-12 inches from two 40-watt cool white bulbs. Run these lights for 14-16 hours daily to match what fewer hours of sun provides.
South-facing windows give you the most options for what you can grow. They catch sun from morning through afternoon in most homes. You can grow almost any herb in a good south window without adding extra lights.
West-facing windows work well for herbs that handle some shade. They get strong afternoon sun that many plants love. East windows offer gentle morning light that suits mint and chives well.
North-facing windows pose the biggest problem for indoor herb gardens. They rarely get direct sun at all in northern areas. You will need grow lights to keep most herbs happy in these dim spots.
Match your herb choices to the windows you have in your home. Put sun-lovers in your brightest spots near south or west windows. Give shade-loving herbs the darker corners where they can still thrive. This matching lets you grow fresh flavors no matter what light your home has.
Read the full article: Growing Herbs Indoors: Complete Guide for Beginners
