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Why Are My Seedlings Dying? 11 Possible Reasons

Watching seeds sprout and grow into healthy seedlings is so satisfying. After all that hard work, the last thing you want to see is those seedlings start to struggle.

The good news is plants are resilient, and many seedling problems can be fixed.

If you’ve been asking yourself, “why are my seedlings dying?” you’ve come to the right place. I’ll show you 11 of the most common reasons why seedlings die and what you can do to fix it. With a little tender loving care, many seedlings can bounce back and grow into strong and healthy plants.

An unhealthy tomato seedling. Knowing answers to the question Why are my seedlings dying helps you treat and prevent the most common issues.

Why Are My Seedlings Dying?

Identifying the cause of why seedlings are dying can be tricky. Here are some of the top reasons why seedlings die, how to recognize them, how to prevent them from happening again, and some possible fixes.

1. Damping Off

A seedling showing signs of damping off.

Damping off is a plant disease that’s common in excessively damp conditions. It lives in soil and is one of the most common reasons why seedlings die.

Once you know the signs, damping off is easy to recognize. Stems develop weak, thin spots that may look watery. Leaves wilt and turn gray or brown. You may also see a fluffy white growth on parts of your plant.

Unfortunately, if your plants already show signs of damping off, there’s no way to save them. The best action is to throw them out and start over again.

How to Prevent Damping Off

If you do see damping off, clean all of your tools thoroughly to make sure the fungus doesn’t spread to your next batch of seedlings.

Use a soilless seed starting mix and avoid starting seeds in garden soil.

2. Other Fungal Diseases

Seedlings with fungal disease.

Other fungal diseases can affect seedlings as well. These are often caused by leaves that stay wet too long or infected soil that splashes up onto the plant when watering.

To prevent fungal diseases, try not to get water on the foliage, use a soilless seed starting mix, and ensure your plants have good air circulation.

Use a spray bottle to water gently at the base of the plants rather than overhead or water from below using a drip tray. Pour water into the tray for plats to pull up through the drainage holes in their containers.

3. Excessive Humidity

Seedlings under a humidity dome.

Humidity domes are helpful for trapping heat and moisture, but you know what they say about too much of a good thing. It’s not good anymore. Too much humidity can lead to mold growth, especially when there is a lack of air circulation.

Mold and other fungi thrive in damp, moist conditions. To fix these problems, increase air circulation by rotating the seed trays, using a fan, and making sure plants aren’t too crowded.

If you’re using a humidity dome, take it off for at least a few hours each day to give the seedlings better air circulation.

4. Too Much or Not Enough Water

Watering pots of seedlings.

Overwatering or underwatering are both common things that lead to the question of why my seedlings are dying. Too much water causes root rot, and not enough causes plants to shrivel up and die.

But how do you know if you’re watering too much or too little? Here’s what to look for.

How to Tell When Seedlings Have Enough Water

The seed starting mix should be moist but not soggy or dripping wet. If you squeeze some in your fingers, it should hold together well and feel wet. If water drips out when you squeeze it, it’s too wet.

If the mix feels dry or doesn’t hold together when you squeeze it, it needs more water.

How to Prevent Over or Underwatering

Soil can easily dry out in small seed trays, especially if seedlings are in front of a window where water evaporates more quickly. Check on your plants at least twice a day and add water whenever the top of the soil looks dry.

The containers you’re using should have drainage holes on the bottom. This lets excess water drain out, so it doesn’t stay trapped around the roots of your plants.

If you’re watering from below, don’t keep the drip tray full. Add as much water as the plants can pull up within a few hours.

5. Wrong Temperature

Seedlings that are wilting.

Another reason why plants die is the temperature isn’t right. It may be too hot, too cold, or fluctuate too much, and the seedlings don’t like it. Certain plants are picky about what temperature they need to grow, and they’ll become weak or fail to grow if they don’t have the right temperature.

A common sign that seedlings are too cold is brown on the edges of the leaves. Plants that are too hot may wilt or curl their leaves.

To fix temperature problems, research what the ideal temperature is for your particular plants. Try to provide that by heating up or cooling off the area where your seedlings are kept.

6. Not Enough Light

Seedlings in low light conditions.

Light is one of the most important things that plants need to grow. If they don’t get enough light, plants won’t be able to photosynthesize. Without proper photosynthesis, seedlings turn yellow or white and eventually die.

Leggy stems are another reason why seedlings die from a lack of light. When they don’t have enough light, plants try to reach for it resulting in long, thin stems that are weak and spindly.

To ensure your plants have enough light, move them directly in front of a large, sunny window or get a grow light.

If you’re using a window, make sure it gets 6-8 hours of direct sunlight each day. Indirect sunlight isn’t enough to keep seedlings healthy, they need the energy from direct sunlight.

7. Too Much fertilizer

Pouring liquid around seedlings in seed starting tray cells.

Another reason you might ask, “why are my seedlings dying,” is because they got too much fertilizer. This is another example of how too much of a good thing isn’t good anymore.

Fertilizer helps grow strong and healthy seedlings, but too much can damage plants by burning them or causing them to grow too fast. If you’ve fertilized recently and notice the stems are becoming tall and weak, it was probably too much fertilizer. Brown, yellow, and crisp edges on leaves are signs of fertilizer burn.

To fix it, use water to flush the extra nutrients away. Ensure the container has good drainage holes and place the plant in a sink or outside. Water thoroughly, allowing the water to flow through completely and drain away, pulling the extra fertilizer with it.

To prevent overfertilizing, wait to fertilize until your seedlings have their first set of true leaves and dilute the fertilizer to 1/4 of the suggested dose.

8. Weak Stems

Seedlings that are getting tall or leggy.

“Why are my seedlings falling over?” is another question gardeners ask when their seedlings start to struggle.

Weak stems are most often caused by not enough light, but it could also be too much fertilizer, overcrowding, or something else. Weak stems eventually flop over when they can’t support the weight of the plant anymore.

To fix weak stems, ensure your plants have plenty of light, the right amount of fertilizer, and plenty of space to grow.

If they’re not too bad, you can usually repot seedlings with weak stems. Bury most of the stems in a deeper container.

9. Overcrowding

Seed starting tray cells with multiple seedlings in each cell.

Starting many seeds in one container is common, and it has many benefits, but they can’t stay crowded for too long. When seedlings are too close together, they compete for resources like soil nutrients, water, and light. This leads to weaker seedlings overall and the resulting quest to figure out why did my seedlings die.

Overcrowding also limits air circulation leading to problems like mold and other fungal diseases. Once they develop their first set of true leaves, plants need space to grow.

To fix overcrowding, thin the plants by separating them into different containers. If the roots are too tangled up to be easily separated, snip away extra plants with scissors and leave the roots alone.

10. The Container is too Small

Seedlings that are showing signs of being root bound.

Another reason why seedlings die is they don’t have enough room to grow. Seedlings can quickly become root bound in seedling trays or small containers.

Unless you started with fairly large containers, most seedlings need to be potted up before it’s time for them to move out to the garden.

If you see roots growing out the bottom of your container, that’s a sure sign the seedlings need more space. To fix it, get some potting soil and larger containers and repot the seedlings.

11. Seedlings weren’t Hardened Off

Tomato seedlings that weren't properly hardened off prior to planting.

If you’re asking why my seedlings are dying after moving them outside to the garden, it could be transplant shock.

Inside, young plants are pampered with comfortable, predictable conditions. Outside, the world is a lot different. Sun, rain, wind, and pests can all affect seedlings in unpredictable ways.

To avoid transplant shock, give your seedlings time to get used to being outside slowly by hardening them off for about a week before planting them in the garden.

Finally, Some Answers to Why Seedlings Die!

A seed starter tray of butternut squash seedlings.

Hopefully, these tips help you get back on track to growing happy and healthy seedlings. With this information, I hope you never have to ask, “why are my seedlings dying?” again!

To learn more about growing healthy seedlings, head to the Seed Starting page on our website. We’ve put together many resources to help you every step of the way. You’ll find information on planting different kinds of vegetables, herbs, and flowers, how-to guides, product recommendations, and much more to help get your garden off to a great start.