Leggy Seedlings: What Causes Them and How To Fix Them

Can you fix leggy seedlings? The answer is Yes! If caught in time. Seedlings falling over and dying because they are too leggy is only one sign they are not getting enough light.

Starting up your own seedlings can be such fun. Not only is it a great skill for all homesteaders and growers alike, but there is also such satisfaction in watching tiny seedlings poke out their heads from the dark healthy soil. 

Be it for your vegetable or perennial garden, starting seeds can save you money.

However, starting seedlings can be a challenge. Leggy plants are a problem that many growers face. When they don’t receive enough light, seedlings will quickly stretch their necks to search for more light. 

I have been starting my own seeds for several years now. Because of our late frost date, I usually don’t start seeds until March and April. 

We northern gardeners have an extra obstacle when it comes to starting seeds indoors.

For many years I kept saying that I had no green thumb when it came to growing plants indoors. Everything wanted to keep dying.

If I managed to keep something alive until I was able to plant it outside, it would thrive. 

I troubleshot as best I could, but never knew exactly what it was that was preventing strong growth in my plants.

My plants grew leggy, and eventually fell over and died. The fragile stems could no longer handle the weight of the leaves.

Leggy seedlings are telling you something is wrong. Healthy plants grown outside are usually not leggy. 

The good news is that there is something you can do about it if caught in time. Prevention is the best medicine, but there are other tips to deal with leggy plants.

The best way to prevent leggy seedlings is to know what causes them in the first place. An understanding of what causes leggy seedlings will help give you tips on what to do to prevent leggy seedlings in the first place.

What are Leggy Seedlings? 

Seedlings are described as being leggy when they grow very tall and skinny. The most noticeable trait is that there are very few leaves in comparison to the height of the plant.

Taller is not always better in the plant world. They may also be pale yellow and look unhealthy. 

What Causes Leggy Seedlings

The main cause of leggy seedlings is a lack of light. However, that is not the only factor that comes into play.

I started some flower seeds and as soon as they sprouted they became leggy. They got light, but they were too far off from the grow light.

Insufficient or uneven access to light is a common problem of legginess in plants. 

Light can be a challenge indoors. The amount of sunlight that we receive in late winter-early spring is not enough for plants to grow a strong root system.

You’ll see them bending towards the light. Cloudy and overcast weather also causes seedlings to stretch towards the sun more than they normally would.

Too much heat and inconsistent moisture can also contribute to legginess, although this is usually a secondary problem. Too much heat can lead to a rapid growth spurt, causing legginess.

This usually doesn’t happen unless you use a heating mat for too long. 

Inconsistent moisture prevents a seedling from growing a strong stem and leafing out well. Seedlings may also grow leggy if they do not get enough water.

Poor soil with not enough drainage will also cause seedlings to struggle to absorb the necessary water and nutrients. That’s why it’s important to use the proper seed stating mixture when planting seeds. 

Common causes of leggy seedlings are insufficient light, lack of consistent moisture, and too much heat.

Tomato seedlings growing in a plastic multi-tray on a sunny windowsill. Leggy seedlings can be a challenge for growers.

How to Fix Leggy Seedlings

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Get A Grow Light

The first thing to do to fix leggy seedlings is to give them more light. A lack of light is the basic problem with leggy seedlings, and getting a good grow light will make a huge difference.

A lot of problems that come from starting plants indoors stem from a lack of light. Here in Northern Canada, we have short days in the early Spring.

Leggy seedlings are a common problem we have. With freezing temperatures outside, plants need to be started indoors.

Unless you have a large south-facing window that gets hours of direct sunlight, you need to grow lights to grow healthy seedlings. 

After I got these grow lights and started using them, my plants started to really thrive. For the first time, my seedlings grew bushy plants, with many leaves. 

Setting up a grow light source is as simple as a shelving unit, plus a set of grow lights. I received a pack of 6 lights, but am currently only using 4 of them.

You can start a number of plants with 2 grow lights. 

If you are already using grow lights, and your plants are still leggy, move them closer to the light. Either move the light down or lift your planting trays.  

Make sure your plants receive a minimum of 12 hours of bright light every day. 14-16 hours of light is even better. 

Turn Heat Mats off 

Using heating maps can help start seedlings indoors, but if your seedlings are starting to look leggy, feel free to turn them off.

Heating mats are especially helpful when starting seeds in a greenhouse when outside conditions are still cold. However, you rarely need an indoor heat mat inside.

Too high temperatures can cause rapid growth that makes the plant shoot up and up.

Using a heat map that has a built-in thermostat control and temperature probe can help you manage the heat better. 

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Add movement

A light wind from an oscillating fan can help strengthen your seedlings.

Don’t turn the fan on full blast, especially not at first! You want to mimic a gentle wind outdoors. Tickling your seedlings with your hands does the same trick.

Airflow also helps to prevent fungal diseases and damping off. 

Use a fan even if the plants aren’t leggy. It will help with hardening off once you bring them outdoors. Last year, I used a fan because my growing room was really stuffy.

This turned out to be a great idea in more ways than one!

Transplant Leggy Seedlings

Just bury the leggy part! Can you really bury leggy seedlings deeper in the soil? 

There are certain plants that won’t do well with this method, but plants such as tomatoes and peppers usually do well when planted deeper.

If your plants have weak, thin stems, there is a chance that they will rot away once buried under damp soil. 

When your plants have their first set of leaves (true leaves, not seed leaves), they can be transplanted. Giving floppy seedlings space and fresh soil will help to strengthen them.

leggy seedlings

The first matter of business when dealing with leggy seedlings is adding more light.

Legginess in seedlings is not only unsightly, it also indicates weak seedlings. These might fail when transplanted if the problem is too severe. Taking action right away is crucial if you want a leggy plant to recover.

It can get really discouraging when you take the time and trouble to plant seeds, and end up with weak and frail plants that just want to keep dying!

I really thought I had no green thumb to grow plants indoors. Once they were outside in our main garden, plants thrived! Turns out, the seedlings just needed enough sunlight. 

Lack of light is the main cause that will cause legginess in plants, but if they are getting sufficient light, then look to other factors, such as insufficient moisture, too much heat, and no air movement. 

You will see a marked improvement in a couple of days.

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