Watch Out for Leggy Seedlings – Here's How to Save the Ones that Are Already Spindly, and How to Keep It from Happening Again
Are your seedlings tall and floppy? There's a simple reason why. Learn how to even out growth and maybe even save the ones you think are too far gone.
Heather Rhoades
Seed starting is a joyful spring tradition. It’s usually the first time you get to put your hands in the dirt, and it’s a great way to bring a little bit of greenery into your dark winter world.
That’s why it can be extra frustrating when something goes wrong. If this is what the beginning of the gardening season looks like, what does that mean for the rest of the summer? Whether it’s damping off, fungus gnats, or leggy seedlings, bumps in the indoor seed starting road are always a pain.
Let’s take a closer look at leggy seedlings, including what causes them, how to save them, and how to protect your future plants from a similar fate.
Article continues belowWhat Are Leggy Seedlings?
At first glance, leggy seedlings might look like they’re on the right track. After all, you want your plants to grow, don’t you? You do, but not like this. Leggy seedlings are tall, thin, and pale. They may not be able to hold themselves upright, or they may be stretching out at an angle, craning and reaching for the nearest light source. This appearance is due to a stress response called etiolation, and it’s not the good kind of growth.
On top of being too tall to stand up, leggy seedlings have put too much energy into stem growth, usually at the expense of the root system. In other words, they’re starting out life at a severe disadvantage.
What Causes Leggy Seedlings?
At the most basic level, leggy seedlings are caused by a lack of light. Unfortunately, even the sunniest window provides light from only one angle, and glass filters out significant intensity. This is why seedlings grown next to a window are so often leaning toward it, looking ready to jump outside and plant themselves. (A phenomenon called Phototropism).
Maybe you don’t keep your seedlings by the window – maybe you use grow lights. Well, you’re one step in the right direction, but it’s still possible to get leggy seedlings even with grow lights. That’s because many people leave too big a gap between their seed trays and their light source. An LED grow light (the kind that’s most often sold these days) should be hung 12 inches (30 cm) above seedlings. It’s important to continue to raise the light as the seedlings grow, to prevent scorching.
While light is the most common culprit, there are a few other things that could make seedlings grow leggy. The totally still air you often find in homes can lead to weak stems. Set up a fan or pet them occasionally with your hand.
High heat could also cause rapid growth. If you germinate your seeds under plastic wrap or a clear plastic dome like this one, make sure to remove it as soon as green shoots appear. Otherwise the excess heat will trick the seedlings into growing too quickly.
The Problem with Leggy Seedlings
Leggy seedlings aren’t necessarily doomed, but they’re starting life with some hurdles that they’ll waste important energy overcoming. If they’re too tall and floppy, it’ll be hard to transplant them outdoors. Plants that rest on the ground are much more susceptible to pests and disease. They’re also more likely to be blown over or even snapped by wind and rain.
How to Prevent Leggy Seedlings
The best thing you can do for your seedlings is to start them under a good-quality grow light, like this one from Amazon. If you absolutely have to grow them next to a window, be sure to turn them 90 degrees every day to ensure even growth. A south facing window is best (if you’re in the Northern Hemisphere).
How to Fix Leggy Seedlings
Can you save a leggy seedling? It really depends on the plant. Tomatoes, tomatillos, and eggplants are completely fine if they get leggy. This is because they can grow new roots along their stems. How deep can you plant tomatoes? Just break off the leaves of the bottom two thirds of the plant and bury it up to the remaining leaves. You can even trench plant tomatoes to give the roots warmer soil and better access to water.
Some other seedlings, like broccoli and other cole crops, can be buried up to the first set of leaves when transplanted. They won’t grow any roots out of their stems, but at least the soil will help stabilize them.
