What Kind of Light for My Indoor Tomato Plants?

Tomato plants are a challenge to grow indoors.

Tomato plants require a lot of good quality light in order to grow and produce fruit. Growing tomatoes indoors can be difficult -- it is a challenge to simulate the direct sunlight that's best for them. You'll probably have the most success with dwarf varieties bred for indoor growth.

Spectrum

Sunlight provides the complete spectrum of light rays that tomato plants require. If you cannot supplement your tomato plants with light from a clean, south-facing window, choose bulbs that are high in the red and blue spectrum (necessary for photosynthesis).

Intensity

Light intensity is measured in foot-candles. Most tomato plants require medium to high light, and fall into the 500 to 1,000 foot-candle range. This means they require, per square foot of growing space, an output of at least 15 watts of light.

Types

Fluorescent tube light bulbs provide the best artificial light for plants. Standard T12 fluorescents, high output (HO) T8 and T5 fluorescents, or compact fluorescents (CFL) are all good choices for tomato plants. Incandescent light bulbs should be a distinct second choice -- they usually provide adequate red spectrum, but not enough blue light and too much heat.

Considerations

The closer the light, the better your results -- but not too close. Keeping lights 4 to 24 inches from the plant is a good range. Remember, also, that tomato plants need darkness. Keep the lamps on for about 12 hours per day and then turn them off.

Varieties

Dwarf tomato varieties bred for container and indoor growing will do best in artificial light. Popular varieties include Tiny Tim, Pixie Hybrids, Small Fry and Red Robins.

References

• University of Missouri Extension: Lighting Indoor Houseplants
• University of Illinois Extension: Tomato
• Tomato Dirt: Using Fluorescent Grow Lights to Start and Grow Tomatoes Indoors