Tall and Spindly Tomato Seedlings

I start my tomato seeds indoors, with fluorescent grow lights about 24″ above the trays. Every year, the seedlings grow tall and spindly, and they’re very fragile. What should I do? -David

The main reason for tall, spindly tomato seedlings is a lack of light. As the plants strain toward the light, they grow taller, thinner, and more fragile. To help with this, you can:

  • Increase Light: Lower your light fixtures, increase the wattage, or raise your trays to get them closer to the light source.
  • Provide Sunlight: Grow lights are great, but they’re no match for pure sunshine. As soon as the weather allows, move your plants to a spot with plenty of natural sunlight, even if it’s an indoor window.
  • Encourage Branching: Pinch back the tops of your plants as they grow, to encourage them to branch out.
  • Transplant Correctly: When you transplant your seedlings into the garden (or into pots), plant them deeply so that at least half to two-thirds of the stem is buried. Some gardeners bury tomato plants all the way up to the topmost leaf cluster. The spindly stem will sprout roots and become part of a deep, strong root system, and the top part of the plant will quickly grow to make up for it.

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  1. Thank you for the sunlight information. I have four shelves of single T12 grow lights, but it is my first experience with growing any seeds indoors at anytime. I untangled my drooping spindly plants and tried loosely tying them up. We live in IA and don’t have a lot of sun, but I have gotten set up with two south windows in order to give them what daily sunlight we have.

    At first I didn’t think I was watering the seeds enough and now I think I am watering them too much. I am watering them from the bottom.

    Do plants like some darkness? OR now that they are spindly should I keep the lights on them day and night? Thank you so much for coming to my rescue. Cecilia


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