Leggy Lettuce Seedlings – Causes & Treatment

If you have ever tried planting vegetables, you will admit that your seedlings becoming leggy is a nemesis that is difficult to avoid. Whether you are planting tomatoes or lettuce, the seedlings always find a way to thin out and become reedy.

This can sometimes be discouraging, especially for anyone just starting the farming journey. It means precious hours tending the seedlings go to waste, and the money used to get the seedlings no longer matter.

Your anticipation of having your homegrown vegetables also disappears into thin air. It is not so good for seedlings either. Reedy seedlings are harder to transplant and have a lesser chance of surviving conditions of the natural soil and weather. They are also more vulnerable to pests and diseases.

Where they eventually grow, the growth could be stunted, thereby affecting the yield. This is why it is essential to prevent leggy seedlings. Or if that is too late, try to fix them by making the stems hard enough for transplanting.

In this article, we examine the causes of this occurrence and how best you can prevent or correct it, whichever the case is.

What Can Cause Leggy Lettuce Seedlings

Many reasons could be responsible for the reedy stems of your lettuce seedlings; we highlight all the possible causes below.

Inadequate Light

Most times, the reason your lettuce seedlings have leggy stems is that they are deficient in light. While it is great to start your seedlings indoors as it gives you a headstart, you can lose this advantage if your seedlings are not exposed to light properly. When the light is faint, or the source is irregular, your seedlings are forced to stretch towards it.

This leads to extended, thin stems that eventually become too weak to support themselves.


The above-average temperature that you expose your seedlings to is likely responsible for their reediness. Too much heat makes the lettuce seedlings grow fix leggy seedlings because heat functions as a catalyst for growth. When the heat is too much, your seedlings are forced to grow faster.

So they will start growing taller even before sprouting leaves. This abnormal growth leads to thin stems that may not be able to bear their weight.

Poor Watering

Lettuce seedlings need water to grow; it is how they get access to soil nutrients and develop. If you water them irregularly or only water the top without ensuring the water gets deep into the roots. They will thin out before sprouting leaves. You will notice the effects of this in their unusual skinniness before they eventually die off if you continue to deny them water.

Crowded Seedlings

It is not only humans that need their personal space to grow; seedlings even need it more. Packing seedlings into a tight space creates fierce competition for the available nutrients, air, and light. Since the available resources are not enough, all seedlings will extend towards it. The sharing will create a bunch of tall tinny seedlings falling over one another.

A Higher Percentage Of Ammonia To Nitrate In The Soil

One of the essential nutrients needed for lettuce seedlings to grow is nitrogen. However, this nutrient is only beneficial if it is in the right percentage of ammonia to nitrates. Nitrates are essential as the seedlings need them for growth and strength.

If there is an imbalance where the soil is having more ammonia than the essential nitrates, the result is frail reedy seedlings trying to touch the skies.

How To Prevent And Fix Leggy Lettuce Seedlings

Now that we know the likely causes of your reedy lettuce seedlings. It is crucial to understand how to prevent it and, better still, fix the ones you already have.

Improve The Lighting

Most times, when your seedlings grow leggy, the cause can be traced to lighting. So it is only right that light should be your priority when it comes to preventing or fixing this. Therefore, you should try to provide more light for your seedlings, either artificially or naturally.

If you want to use natural sunlight, that might involve taking out the seedlings every day. It would be best if you did not rely on the rays of light coming in through the window sill. However, you don’t necessarily need to do this; there is artificial lighting, which is more effective.

Your seedlings need between twelve and sixteen hours of light daily when they start growing. It is nearly impossible to get that much light naturally, so artificial light is a better option. You can use fluorescent light or, better still, get LED to-grow lights designed specifically for that purpose.

These lights should be placed between two to three inches from the seedlings. This is close enough for the seedlings to feel without stretching and far enough not to burn the fragile leaves. For ease, it is advisable to get a timer for the lights.

When picking out lights, it is crucial to use the right artificial lights. This is because the lights come with varying ratios of red to blue light.

It is a balanced combination of both lights that makes the seedlings’ growth balanced. So pay attention to how your seedlings are reacting to the light.

If they are growing reedy despite the right lighting conditions, you might have to replace the lights. Then, until you can supply more, alternately rotate various trays in front of the light each day.

What Makes Solution Great

Lighting is the primary problem, so fixing it is the best chance to improve your seedlings.

Regulate The Temperature

Once your seedlings start growing, it is time to modify the temperature to fit this development stage. For your seeds to bud, the temperature required is usually between 75° F and 80° F.

But once it has become a seedling, a lower temperature of between 55° F and 70° F is needed. You have to note these changes and monitor the room temperature to ensure it is at an optimal level for healthy growth.

Why This Is A Great Solution

Keeping optimal temperature is not only good for lettuce seedlings but all others too.

Proper Spacing

Organize your seedlings from the moment you are planting the seeds. There is no point in waiting until the time you want to transplant to do this. Once they start germinating, make sure there is a gap of up to two inches in-between.

This will prevent unhealthy competition for light, air, and nutrients.

Why This Is A Great Solution

It prepares the seedlings to thrive in the natural soil and weather. In addition to enhancing air circulation, it lessens competition for nutrients, area, light, and water.

Adequate Watering

Consistency in watering is essential; it must be an everyday thing, not when you remember. Also noteworthy is that the watering should be comprehensive. You should make sure the water is getting to the roots each time you do it.

The point of watering is not to wet the leaves but the soil, so make sure you’re doing that.

Why This Is A Great Solution

It gives your seedlings the much-needed resources and makes you pay more attention as well. The roots of the plants grow deeper when they receive water from below, which strengthens the plants.

Brush Against The Stems Or Use Fans To Simulate A Natural Breeze

By sweeping your hands against the stems of the lettuce seedlings or using a fan to blow air on them, you simulate natural wind. It is thereby forcing the seedlings to adapt and develop sturdier stems. If you decide to use a fan, don’t keep it on for too long.

Doing so might air out the moisture around the seedlings, and you don’t want this.

Why This Is A Great Solution

The easiest and cheapest way to harden them enough for natural conditions. Additionally, damping off and fungus diseases are avoided by adequate airflow.

Transplant As Soon As Possible

People make the common mistake to keep the seedlings indoors for too long. Transplant your lettuce seedlings as soon as they are mature enough. A process known as “hardening off” involves gradually exposing seedlings that were grown indoors to the elements. This is why hardening them beforehand is essential.

You should also expose them to direct sunlight and natural weather before transplanting. In most cases, starting with a few hours in the shade and gradually increasing the time and amount of direct sunlight.

The seedlings become stronger as a result and are better equipped to withstand difficulties like wind, rain, hot sun, or cold temperatures. It will do the lettuce seedlings much good.

Why This Is A Great Solution

By not keeping them any longer than necessary indoors, their productivity increases. They will be strengthened by this and inspired to prepare to “move house” into your garden’s vast, open space!

Reduce Ammonia To Nitrate Content In Your Potting Soil

Instead of sticking with the fertilizers, you are already using, which may contain urea or ammoniacal nitrogen, apply hydroponic fertilizers to your seedlings.

Why This Is A Great Solution

It is cost-effective when you use hydroponic fertilizers and remove the risk of too much ammonia. Also, the use of nutrient solutions that contain the nutrients nitrate and ammonium in the proper concentrations lessens the ammonium’s toxic effects.


There is no ultimate solution to fixing your leggy lettuce seedlings and hardening them enough for transplanting. The solution you adopt will be determined by what you think is the actual cause of the problem; that is why proper troubleshooting is crucial.

You should pay attention to everything you do with regard to the seedlings from the moment you plant them. That way, it is easier to realize what went wrong and correct it. However, eighty to ninety percent of the time, the lighting is the basis of the problem.

So, make sure your seedlings have access to optimal lighting all the time. It will save you the pain of watching your carefully tended lettuce seedlings turn reedy and wither away.

Once you have taken care of the lighting, the rest is easy to deal with.

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