6 Surprising Causes For Leggy Cucumber Seedlings (How To Fix)

Are your cucumber seedlings looking long, thin, and weak? You are dealing with leggy cucumber seedlings. No need to worry, though! We’ve got you covered.

In this blog post, we’ll provide you with the causes of leggy cucumber seedlings and practical tips for preventing and fixing this issue, ensuring the growth of robust, healthy and fruitful cucumber plants. Rest assured, we have all the information you need to succeed. Let’s dive in!

Cucumber seedlings become leggy due to a lack of light. When they don’t receive enough light, they stretch out in search of more light, resulting in long, thin, and weak stems. To prevent leggy cucumber seedlings, it’s important to provide adequate light, such as 14 to 16 hours of light per day, and avoid over-fertilization. By following these tips, you can promote healthy growth and prevent leggy cucumber seedlings.

Main Causes of Leggy Cucumber Seedlings

Main Causes of Leggy Cucumber Seedlings
Causes of Leggy Cucumber Seedlings

1. Insufficient Sunlight

A lack of sufficient light is one of the main causes of leggy cucumber seedlings. When your cucumber seedlings don’t get enough light, they tend to stretch out in search of more resulting in weak stems.

As a result, the weakened stems are unable to support the weight of the cucumber plant. Moreover, the lack of light affects the seedlings’ leaf production. Weakens their root system, which further contributes to their lanky growth.

This is particularly common when starting seeds indoors or in a window that lacks sunlight.

If your cucumber plants have leaves and are elongating towards the window, it’s a clear indication that they’re not getting enough sun. This is often an issue for seedlings in apartments with natural lighting.

For growth and development, cucumber seedlings need access to sunlight for at least 12 hours each day. However, it can be challenging to provide this amount of light in an average apartment setting. That’s why artificial lighting may be necessary.


To prevent cucumber seedlings from growing long and weak due to a lack of sunlight it’s crucial to ensure they receive light. Cucumber seedlings need about 14 to 16 hours of light every day to grow well and avoid becoming leggy.

If natural sunlight is not sufficient you can use light sources like grow lights to supplement the lighting.

Position the grow lights 2 to 4 inches above the seedlings and keep them switched on for around 14 to 16 hours each day. Additionally, it’s important not to overcrowd the seedlings, as this can cause shading and worsen the light issue.

By ensuring proper light, you will encourage healthy growth and prevent leggy development in cucumber seedlings.

2. High Temperatures

In addition to insufficient light, high temperatures can also contribute to leggy cucumber seedlings. When the temperature is too high, it promotes growth, resulting in tall and thin seedlings. For cucumber seedlings to thrive, they prefer temperatures ranging from 70–80°F (21–27°C) during the day and 60–70°F (15–21°C) at night.

For growth, cucumber seedlings require an optimum temperature of 20–22 °C. When temperatures drop below 10 to 16 °C, it can have an impact on the growth of cucumbers.

Leaves may start to curl, and seedlings might even fall off. It’s crucial to shield the seedlings, from abrupt temperature shifts until they become resilient enough to withstand them.

The water used for irrigation also plays a role in maintaining conditions. It’s best to use water with a temperature of 20 to 25°C. Using hard water can be harmful to the seedlings.


To ensure that the temperature remains ideal for cucumber seedlings it’s crucial to place them in a location where they won’t be exposed to changes in temperature.

Taking measures to protect the seedlings from drafts and keeping them away, from radiators is important as well. Heat, combined with air humidity can cause cucumbers plants to wilt and lean sideways sometimes even falling out of their pots.

Regular monitoring and adjustments may be required. If you’re growing them indoors using a thermostat-controlled heating mat can help maintain a temperature for healthy growth.

3. Excessive Use of Fertilizers

If the seedlings suddenly topple out of their pots it might indicate an issue with their nutrition. Excessive top dressing can hinder the functioning of the root system causing the seedlings to grow upward sharply and subsequently fall over. As a consequence, the cucumber seedlings become leggy and stretched out.

Over-fertilization can also lead to burns and other harm to the roots further weakening your cucumber plant.

Especially if you apply an excessive amount of fertilizer rich in nitrogen content, it can result in cucumbers receiving an abundance of nutrients that stimulate rapid and vigorous growth.

Nevertheless, this accelerated growth may cause elongated stems as young cucumber plants prioritize growth instead of developing a strong structure.

There are options available for fertilizing cucumber seedlings through watering or spraying including mineral and organic fertilizers, industrial or traditional ones, complex or single-component ones, as well as two-component choices.

However, it is important to choose the fertilizer that suits the needs of the cucumber plant without surpassing the recommended dosage.

It’s preferable to provide a small quantity of fertilizer rather than overfeeding them since hungry seedlings can still absorb nutrients for recovery.


To prevent leggy cucumber seedlings caused by excessive use of fertilizers, it’s important to follow recommended fertilizer guidelines and use balanced formulations that promote overall plant health without encouraging excessive elongation.

It’s also important to avoid over-application of fertilizers, particularly those high in nitrogen. Instead, provide the seedlings with a balanced compost or fertilizer and avoid excessive amounts.

Additionally, ensure that the soil is well-draining and that the seedlings are not sitting in water to prevent further stress on the plant.

4. Poor Soil Condition

Why else can cucumber seedlings become leggy? Maybe it’s the poor quality of the soil!

This happens because the soil lacks nutrients and becomes compacted making it difficult for the roots to absorb water and nutrients. As a result, the seedlings try to compensate by growing taller in search of air and light, resulting in weak stems.

Soil conditions play a crucial role in the healthy growth of cucumber seedlings. Too dense or crumbly, acidified, alkalized, or saline soil can cause discomfort for the plants and lead to leggy growth.

The roots and stems may not withstand the load, causing the seedlings to fall over. Transplanting cucumber seedlings can be difficult and risky, especially if they are already weakened.

It’s better to prepare the soil at the sowing stage by making it loose and nutritious to promote healthy growth and prevent leggy development.


To prevent leggy cucumber seedlings caused by soil conditions it’s crucial to ensure that the soil is well drained and nutrient-rich. Adding matter like compost, or you can use this variant of the soil mixture: peat, humus, sawdust, sand, mullein (6:1:1:1:1).

It’s also important to maintain a pH level for cucumber growth, typically between 6.0 and 7.0. Additionally avoid compacting the soil by walking on it or overwatering, as these practices hinder root growth and development.

By providing nutrition and optimal soil conditions, you can promote healthy growth in your cucumber seedlings while minimizing legginess.

5. Overwatering

Excessive watering can result in cucumber seedlings becoming leggy as it reduces the amount of oxygen in the soil. This lack of oxygen hinders the growth and development of roots making it difficult for them to absorb nutrients and water leading to stunted growth.

Also, excess moisture provides a thriving environment for a variety of fungi and bacteria. The danger increases if the room temperature is above normal. 

Consequently, the seedlings may elongate in an effort to access air and light, resulting in weak and lengthy stems. Additionally overwatering can contribute to root rot, further weakening the plant and causing it to become leggy.


To prevent leggy cucumber seedlings caused by watering, it is crucial to ensure that the soil has good drainage and that the seedlings are not constantly sitting in water.

Allowing a slight drying out period between waterings is important; only water when the top inch of soil feels dry when touched. It is also advisable to avoid watering as this can encourage powdery mildew growth and other fungal infections.

Instead, focus on watering, at the base of the cucumber to foster root development and discourage leggy growth.

6. Overcrowded Seedlings

Frequent sowing can cause overcrowding among sprouted cucumber seedlings, leading to competition for light and space and a lack of freedom and nutrients for the root system.

When cucumber seedlings are too close together, they can become tall and thin due to competition for light, water and nutrients.

This happens because the seedlings stretch their stems in an attempt to reach light. Additionally, overcrowding can hinder root growth and development which further contributes to the problem of leggy growth.

This can result in thinning and disappearance of seedlings as they struggle to grow in a crowded environment. To prevent this, it’s important to maintain proper spacing during sowing to promote healthy growth and development.


To avoid leggy cucumber seedlings caused by overcrowding, it is important to give them space. It is recommended to space the seedlings around 2 to 3 inches apart.

If you already have seedlings you might need to remove some of the weaker or spindly plants. This will allow the remaining seedlings to have access to light, water and nutrients which will promote healthy growth and prevent legginess.

Can You Save Leggy Cucumber Seedlings?

Yes, it is actually possible to save leggy cucumber seedlings that have grown tall and thin with stems and few leaves. When cucumber plants become leggy it is crucial to identify and address the cause of this growth issue.

As I presented to you above, common culprits may include lighting, overwatering, or excessive use of fertilizers.

Leggy cucumber seedlings often arise when starting seeds indoors. This happens when the seedlings don’t receive light and subsequently stretch out with thin stems. However, if you catch this problem, there are still chances to salvage the seedlings and achieve a successful harvest.

The key to saving leggy cucumber seedlings lies in providing them with light exposure. If they lack illumination you can try moving them closer, to a south facing window, or utilizing artificial lighting sources.

Also, you can use a heating mat. Humidity dome can facilitate root growth while protecting against damping off disease.

Tips for Salvaging the Seedlings

Here are some tips for salvaging leggy cucumber seedlings:

  • Try to catch the problem early: As soon as you notice the seedlings are leggy, take action to save them.
  • Provide more light: Move your cucumber seedlings closer to a south-facing window or provide them with artificial light.
  • Bury the stems: When transplanting the seedlings, bury the stems deeper than usual to help support the weak stems.
  • Improve the potting mix: Use a seed starting mix that is light and fluffy, allowing for better root growth.
  • Avoid overwatering: Overwatering can lead to weak stems and damping off disease.
  • Fertilize appropriately: Fertilize the seedlings with a balanced fertilizer to encourage healthy growth.
  • Thin out overcrowded seedlings: Overcrowded seedlings can lead to insufficient light and leggy growth.
  • Control temperature: Avoid exposing the seedlings to too much heat or too warm of temperatures, as this can exacerbate the problem.

By following these tips, you can save leggy cucumber seedlings and still have a successful harvest in your vegetable garden. Remember to catch the problem early and provide the seedlings with adequate light, potting mix, and fertilizer to encourage healthy growth.

How to Fix Leggy Cucumber Seedlings

How to Fix Leggy Cucumber Seedlings
How to Fix Leggy Cucumber Seedlings
  1. Adequate lighting: Leggy cucumber seedlings thrive with light. If you’re growing them indoors position them near a south-facing window. Use grow lights. Aim for 12 16 hours of light exposure.
  2. Transplanting technique: If your cucumber seedlings have become leggy a helpful approach is to bury the stems when transplanting them into your vegetable garden. Bury the stem up to the set of leaves as this encourages root development and provides better support for the plant.
  3. Spacing: Overcrowding can contribute to leggy growth in seedlings. Ensure that you space out your seedlings appropriately and thin out any ones to allow for adequate light penetration and air circulation.
  4. Moisture: Cucumber seedlings require soil for successful germination. Using a heating mat can help create conditions for germination while a humidity dome aids in maintaining soil moisture levels promoting healthy growth.
  5. Quality potting mix: Opt for a balanced seed starting mix that helps prevent damping off disease and supplies essential nutrients necessary for robust growth.
  6. Avoid overwatering: Thin stems and weak growth can result from overwatering. Water your seedlings when the soil feels dry, to the touch ensuring they receive appropriate hydration without excess moisture accumulation.
  7. Fertilize correctly: Once your cucumber seedlings have grown their set of leaves it’s time to start fertilizing them with a well-balanced fertilizer. Just make sure to read and follow the instructions, on the label carefully and avoid overdoing it with the fertilization.

Can I plant leggy cucumbers deeper?

Yes, you can plant leggy cucumbers deeper to encourage healthier rooting and growth. I recommend digging the hole about 1-2 inches deeper than the root ball. This allows you to lay the seedling at an angle with the majority of the thin stem below the soil line.

As long as the original roots and a portion of the stem remain above ground, the plant will be fine. Burying the leggy part stimulates the formation of new roots all along the portion that was previously exposed.

This thicker root system helps stabilize and strengthen the seedling. Within a few weeks, the plant is better able to support itself and resume normal growth upwards towards the sun.

Tips for Preventing Leggy Cucumber Seedlings

If you’re growing cucumber seedlings and notice that they are getting leggy, there are a few things you can do to prevent this from happening.

Here are some general tips for preventing leggy cucumber seedlings:

  1. Provide adequate light: Cucumber seedlings need plenty of light to grow strong and healthy. Make sure they are getting at least 12-14 hours of light per day. If you’re growing them indoors, consider using grow lights to supplement natural light.
  2. Keep the temperature consistent: Cucumber seedlings prefer temperatures between 70-75°F (21-24°C). Fluctuations in temperature can cause them to become leggy.
  3. Plant the seeds at the right depth: Cucumber seeds should be planted about 1 inch deep. Planting them too shallow or too deep can cause them to become leggy.
  4. Water properly: Overwatering can cause cucumber seedlings to become leggy. Make sure the soil is moist but not waterlogged. Allow the soil to dry out slightly between waterings.
  5. Fertilize appropriately: Cucumber seedlings need nutrients to grow strong and healthy, but too much fertilizer can cause them to become leggy. Use a balanced fertilizer and follow the instructions carefully.

Frequently Asked Questions

Can I save leggy cucumber seedlings, or should I start over?

Leggy cucumber seedlings can be saved by transplanting them into larger pots and burying the stems deeper in the soil. This will allow the plants to grow new roots along the buried stem and become stronger.

What are some signs that my cucumber seedlings are becoming leggy?

Signs of leggy cucumber seedlings include long, thin, and weak stems, small and pale leaves, and a lack of foliage near the base of the plant.

Is it possible to fix leggy cucumber seedlings without harming the plants?

Yes, it is possible to fix leggy cucumber seedlings without harming the plants. By transplanting the seedlings into larger pots and burying the stems deeper in the soil, the plants can grow new roots along the buried stem and become stronger. Additionally, providing adequate light and avoiding over-fertilization can help prevent legginess in the future.

How does proper spacing help in avoiding leggy cucumber seedlings?

Adequate spacing prevents competition for light, allowing each seedling to grow strong and compact, minimizing the chances of legginess.

Andreea Tapu

Andreea TAPU is a passionate gardener with over 5 years of experience in cultivating a wide variety of plants and flowers in her garden. As the author and creator of, she is dedicated to sharing her knowledge and expertise with others, providing practical tips and advice to help gardeners of all levels achieve success and enjoyment in their gardening pursuits.