How to Fix Leggy Seedlings & Prevent It in the Future

Are your seedlings looking like the wavy inflatable man in front of new businesses? You have leggy seedlings, but don’t despair. The problem IS fixable.

You spent hours planting and labeling your seed trays, and the seeds sprouted. Now, the seedlings are too tall and leaning to the side. You heard the term “leggy seedlings” before, but you have no idea what to do now.

If this feels like a scenario that has played out in your gardening world lately, then you are in the right place. Even the most experienced gardeners experience leggy seedlings at times, including me.

We will take a look at what they are, why this is a problem for your seedings, and how to fix it when you see it happening!

Related: Potting Up Seedlings: A Complete Guide for Gardeners

What are Leggy Seedlings?

Leggy seedlings are seedlings that are very tall and skinny; taller doesn’t mean healthy plants, especially if they are brand-new seedlings. These lanky seedlings are weak and fragile, sometimes looking yellow or pale green.

These baby seedlings are struggling.

You don’t have to break out your ruler to decide if your seedling classifies as leggy. Instead, take a look at your other seedlings and see if they look as healthy as that seed tray. Healthy seedlings stay shorter when compared to the leggy ones. Experience gives you a feel for what is normal and what is not.

What Causes Leggy Seedlings?

I sort of neglected these poor little cabbage seedlings. Not only are they leggy, but their soil is dry!

Are you wondering what problem caused the legginess? Here are some of the most common problems that result in leggy plants.

1. Insufficient Light Needed

The nature of seedlings is to grow toward the light. If a light source is too dim or insufficient, the seedlings grow quickly in search of more light. So, it grows leggy and stretches towards the brightest source it senses.

If you have ever put seedlings near a windowsill, you might have noticed your seedlings leaning toward the sun. The sunlight at a window is not enough for seedlings to grow, so they start to bend.

However, a seedling only can gain so much height, and what it gains in height, it sacrifices in width. The seedling might be tall, but the stem is thin and fragile.

2. Too Much Heat

Another common problem is overly high temperatures. If your seed trays sit on a heating mat or have a humidity dome over the top, the extra heat will cause rapid growth.

Once seeds germinate, heat causes them to shoot up, gaining length before leaf production. This makes your seedlings “all legs” rather than developing a thicker stem.

3. Inconsistent Moisture

Inconsistent watering causes a problem, especially since the seed starting mix often dries out between watering days. This causes issues with growing a strong stem and leaf growth.

If plants have inconsistent moisture, you end up with spindly seedlings, and over time, they will die because dry soil prevents roots from accessing nutrients.

4. Lack of Space Between Seedlings

Oftentimes, we start dozens of seeds in one tray, but this decreases the space between each seedling. That’s why you should be sure to thin your seedlings as they grow.

If you don’t thin out seedlings during their early development, the overcrowded seedlings will grow taller as they compete with each other for light.

Are Leggy Seedlings a Bad Sign?

Some seedlings – like these lettuce – grow so fast and get leggy easier than others. I restarted this bunch.

Noticing legginess on seedlings is not a good thing. This means that, rather than developing thick, sturdy stems, your plants are thin and fragile. The taller they get, the weaker they become. These seedlings are top-heavy, and they may flop over and break.

Leggy seedlings are more vulnerable to other problems as well. They are prone to “damping off, which is a condition that causes seedlings to wilt suddenly or they will rot above the soil line.

If you fail to correct the problem, legginess will weaken their stems, stunt the seedlings’ overall growth, and cause them to be vulnerable to pests and diseases.

You might assume that it’s ok because you can plant them deeper outside later. However, not all plants enjoy you doing this. Tomato seedlings don’t mind, but you want to make sure you fix the issue as soon as you notice it happening.

How to Prevent Leggy Seedlings

Like many other things, the easiest and best option is to prevent this from ever happening in the first place. Fixing seedlings takes work, and it’s not always guaranteed to work. Prevention is key. Here are some steps to prevent leggy seedlings in the future.

1. Remove Humidity Domes

Humidity domes on your seed trays aid germination but should be removed after the seedlings sprout. It’s a common mistake you can remedy quickly if you realize it not too long after the seedlings start growing.

Trust me; I did this recently with my broccoli seedlings, and my seedlings were way too tall. Oops!

Related: 7 Best Seed Trays and Pots for Starting Seeds at Home

2. Give Bright Light After Germination

Once you take off the humidity dome, make sure you give bright light immediately. All it takes is a few days with the right amount of light to reverse the problem.

3. Use Supplemental Light

Keeping seedlings by a sunny window is generally not enough light for seedlings to grow. If you want to use a window light, I suggest using a south-facing window. You will need to provide supplemental lights, typically known as grow lights.

4. Keep the Lights Low Over Your Seedlings

When you put up your grow lights, be sure to keep the lights low over the seedlings. If you keep the lights too high, the seedlings may get leggy. Keep the lights a few inches above your seedlings, but LEDs need to be higher because they will potentially burn your plants.

5. Make Sure You Give Enough Light Each Day

Seedlings need a minimum of 12 hours but thrive when they receive 14-16 hours of light. They need 8 hours of darkness as well. A light timer helps with this since it’s easy to forget to turn off your lights.

How to Fix Leggy Seedlings: Step-by-Step

These are the same cabbage seedling as above. I repotted them, and they were much happier.

Well, you didn’t prevent legginess; instead, you have leggy seedlings. The good news is, if you act quickly, you will be able to prevent the issue from getting worse and strengthen the seedlings for future growth.

1. Give Your Seedlings More Light

The first thing you should do to fix leggy seedlings is to provide them with more light. You may need to add another supplemental grow light or upgrade to a stronger light. Another option is to lower the current light to make it closer to your seedlings.

Oftentimes, a grow light setup requires several lights or a larger unit to cover all the seedling trays. Be careful not to have straggler seed trays on the perimeter of your lights.

That happens at times, so rotate the trays that are directly under the light until you can either add more lights or they go outside.

2. Take Off the Heat Mats

If you use a seedling heating mat to start seeds indoors and notice the seedlings becoming leggy, it’s time to either turn the heat mat off or lower the temperature.

Warmth is great for seed germination, but once your seeds sprout, too much heat will encourage your seedlings to grow too fast. You don’t need to encourage them to get taller.

3. Replant Deeper into a Bigger Pot

5 days after repotting into different containers – these leggy seedlings feel better. I’ll up-pot in larger containers in the next 1-2 weeks.

The best way to deal with tall seedlings is to replant the weak seedlings deeper. This comes with a bit of a risk; some seedlings will experience root rot if you do this. However, I generally prefer to risk it and see what happens rather than restart unless it’s only been a short few days.

Replanting seedlings deeper is quite easier. I start by using a container that is deeper than the seed tray they are in and place some dirt into the tray or container. You should use larger seedlings pots when up-poting the seedlings. Then, I create a larger hole to put the seedling into.

You have to be careful because the stem may bend when you fit it into your container. Once it’s into the tray, bury it as deeply as possible and pack soil to the top of the tray.

How Deep Can You Plant Leggy Seedlings

If you are wondering how deep to plant leggy plants, the answer is – it varies. You want to bury the plants enough that the plant isn’t too heavy.

Here are some considerations when deciding how deep to plant them. Staying on the side of caution is always smart!

  • In general, most seedlings don’t mind if you bury their stem up to their first set of true leaves or lateral branches. This is true for brassic seedlings like cabbage, broccoli, and peppers. So, plant up to the lowest set of leaves on the plant.
  • Some seedlings don’t mind being planted deeper. For example, leggy tomato seedlings and tomatillos can be planted up to half underground. You can remove the lower branches and bury the plant past that point.
  • If the plant continues to grow tall, branching, fragile stems, you may not need to bury deeper,m like flowers and herbs.

4. Consider Restarting Your Seedlings

If you are several weeks into seed starting, that’s not an ideal time to restart your seedlings. However, restarting your seedlings is likely the best choice if you are only a few days after germination. It will lead to healthier seedlings for the rest of the season.

This solution to fix floppy seedlings depends on the age of your seedlings and when you need to plant them outside. If it’s early spring and the plants have plenty of weeks before planting outside, it’s safe to restart. However, if you are only a few weeks away, then you have to try planting the seedlings deeper.

5. Focus on Making Your Seedlings Stronger

Sometimes, the solution to fix the seedlings is to make them stronger, especially if you are close to planting them outside. They have to be strengthened beforehand, or they’ll be too weak to plant outside.

Ideally, your plant will have thicker stems that will help transport more nutrients and water throughout your plant. Thicker stems also stand up to wind better, which is an element they need to face outdoors.

Here are a few ways to make your seedlings stronger.

Add Movement to the Air

When seedlings head out into the big garden, they encounter wind. Wind might not seem like a big deal to you, but if the plant lacks the thicker stems needed for support, wind topples the plant over.

One way to strengthen your plants before they go outside is to use an oscillating fan throughout the day. It should provide small amounts of movement; don’t set it on high. This gentle movement will cause the stems to become stronger.

You don’t have to leave the fan on all day; a couple of hours per day is sufficient. You end up with strong plants

I always run my hands over my seedlings as well whenever I water or check on them. It helps to toughen them up!

Adding a small fan has another benefit as well become airflow decreases fungal disease and damping off. So, whether your plants are leggy or not, using a fan is a smart idea.

Fertilize and Water from Below

Another way to increase the health of your plants is to feed them with some fertilizer. After seedlings develop their first set of leaves (or second set of true leaves), it’s time to feed with a mild liquid fertilizer.

You shouldn’t fertilize until they are a few weeks old. True leaves are not the initial two leaves that are heart-shaped.

Seaweed extract and fish emulsion are two excellent options if you want to fertilize seedlings. You should always dilute and follow the instructions.

You should also water and fertilize in the tray the seedlings sit inside. The soil in the container soaks up the water, and you won’t disturb the soil surface on the top of the plants. Since the roots need more water, it makes sense to water from below.

Harden Off Your Seedlings

Before putting your seedlings outside, you have to make sure you harden off the plants. Hardening off is a process of introducing seedlings slowly to life outside.

This process typically takes a process of introducing seedlings outside for a few hours per day, slowly adding more time outside. It helps increase the strength of your plants while giving them a break. It’s like an exercise program for your plants until they’re ready for the real race – living outside.

Don’t let leggy seedlings frustrate you. It’s often part of gardening and having a busy life at the same time. Luckily, with these tips, you can fix any legginess and prevent it from happening in the future!

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