You can grow tomatoes on a windowsill but your success depends on variety choice and how much sun your window gets. Micro and dwarf types work best since they stay small. Most full sized tomatoes won't fruit well with just window light alone.
I tried growing regular tomatoes on my south facing window a few years back and failed hard. The plants grew tall and spindly reaching for light. They made flowers but the flowers dropped without setting fruit. When I switched to Micro Tom the next year, I got ripe tomatoes from the same window. The tiny plants got enough light to produce without stretching out of shape.
The main issue with windowsill tomato growing is light hours. Most windows give plants only 4-6 hours of direct sun per day. Tomatoes want at least 8 hours to flower and fruit well. Even a sunny south facing window falls short of what the plants need during much of the year when days are shorter.
Utah State Extension notes that the smallest varieties work best for windowsills. Plants that stay 1-2 feet tall fit the space and can produce with less light than larger types. Sunny window tomatoes like Micro Tom, Tiny Tim, and Red Robin were bred for these exact conditions. They make fruit even when light levels aren't ideal.
South facing windows give you the best shot at success without extra lights. These windows get the most sun hours in the northern hemisphere. East and west windows can work in summer when days are long. North windows rarely give enough light for any fruiting plant no matter what variety you pick.
I now add a small grow light to my windowsill setup during fall and winter. The plants get natural sun during the day and a few extra hours of LED light in the morning or evening. This bumps my total light hours up to 10-12 per day. The plants produce fruit through months when they would otherwise go dormant.
Start with Micro Tom or Tiny Tim if you want to try windowsill tomatoes. These varieties stay compact and produce cherry sized fruit. Give them your sunniest window and water when the soil surface dries out. Add a small clip on grow light if your window gets less than 6 hours of direct sun. This simple setup lets you harvest fresh tomatoes year round from a sunny corner of your home.
Read the full article: Growing Tomatoes Indoors: Complete Guide
