Why do Tomato Plant Starts Get Leggy? (And How to Fix It!)

If you are at all like me, you cannot wait to start planting seeds indoors to give your garden plants a head start. I started my pepper, tomato and herb seeds. However, the weather in Central Missouri has been quite cloudy that has lasted several weeks. My grow lights, so it seems, were not quite enough to keep my tomato plants from getting leggy. (see picture below). This condition, known as "legginess", when plants stretch to much in search of better growing conditions. Leggy seedlings are fragile and can struggle once transplanted outdoors. Let's look at how this happens, how you can prevent it, and how to fix it if it does happen.

Why do seedlings get leggy?

The main reason for legginess is inadequate light. When seedings don't get enough direct light, they grow tall and spindly, reaching toward the light source. Other factors that contribute to legginess include high temperatures and overcrowding, which causes plants to compete for light and space.

How to Prevent Leggy Seedlings

Provide Strong, Direct Light (This was my mistake.)

Tomato seedlings need 12-16 hours of bright light each day. A sunny windowsill often is not enough, so supplement with grow lights placed just a few inches above the plants. As they grow, adjust the lights to keep them close. Here are the ones I use https://amzn.to/4b5oDo1

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Control Temperature

Warmth helps seeds sprout, but once they have germinated, temperatures that are too high (above 75) encourage weak, fast growth. Keep seedlings in a cooler environment (65-70) to promote sturdy stems.

Give Them Room to Grow

Crowded seedlings stretch to outcompete their neighbors. Thin them out or transplant them to larger cups early so each plant gets plenty of light and air circulation.

I separated and transplanted each seedling. I buried the roots and stem as deep as possible.

Starting Your Spring Garden Indoors

If your tomato seedlings are leggy, don't worry. When you transplant them, you can bury them deeply--tomatoes will grow roots along their buried stems, making them stronger. Starting seeds indoors takes practice, but with good light, proper temperatures, and enough space, you will grow strong, healthy plants ready for the garden.

Spring is just around the corner--so start those seeds and get ready for a great growing season!