How to Save Leggy Seedlings and Prevent Spindliness (2024)

In the human world, there are lots of benefits to being leggy. You can reach things that are on the highest shelf, you can see above heads in a crowd, and of course, let’s not forget how much everyone loves those leggy supermodels!

However, in the plant world, being leggy is something to be feared. Legginess in seedlings can be caused by a variety of factors. A leggy seedling is a plant that has grown too tall for its own good.

It’s usually a result of poor planting and care, but it can also be caused by harsh conditions in which there was not enough water or sunlight.

If you’ve noticed that some of your seedlings have become tall and spindly, don’t despair! You can follow several methods if you are looking for information on how to save leggy seedlings. Follow these tips.

What Does it Mean if a Seedling is ‘Leggy?’

Leggy seedlings are those that have, essentially, grown too big for their environment. A seedling might appear to be spindly and stretching toward the sun.

Technically, any plant can become leggy, but this situation is far more common in plants like zucchini, kale, broccoli, lettuce, beets, and tomatoes.

Beets are especially prone to becoming leggy because they sprout numerous seedlings from just one seed ball. They are far more likely to become overcrowded as a result.

When a seedling is leggy, it is because they have stretched toward their light source, trying in vain to get more sun when it’s just not available. It is most common in seedlings started on a windowsill rather than those that are grown beneath grow lights (where sunlight is more readily available and is usually more evenly distributed among the plants).

Seedlings that have become leggy generally have pale, thin stems and few leaves. The leaves they have are usually quite small.

Why Are Leggy Seedlings Bad?

Although legginess won’t kill your plants, it is definitely not something you will want to deal with when it comes to your plants. That’s because legginess can cause stems to become stunted, often rendering them useless when it comes to fighting off pests and diseases.

It can be harder for these seedlings to stay upright. The stems are more likely to bend and break, and you might find your plants collapsing into the soil. This direct contact with the ground can lead to an increased likelihood of disease and rot.

Plus, it is tougher to harden off seedlings that have become leggy. Their stems are so weak and fragile that they will have a tougher time holding up to the rain and wind once planted in the ground.

Causes of Leggy Seedlings

If you’re realizing that some of your seedlings have become leggy and are panicking because of all the risks described above, take a moment to breathe deeply. The good news is that you can almost always save leggy seedlings and that they will go on to become strong, healthy plants with productive yields.

Here are some of the most common causes of leggy seedlings, so that you know how to prevent them in the future.

1. Poor Lighting

The number one cause of leggy seedlings is poor lighting. Plants are naturally inclined to grow toward the light, so when the light is too far away (or perhaps not bright enough), your plants will grow more quickly to reach that light.

Translation – too much stem, too little time.

A seedling can only grow so much before it develops a thin, fragile stem. This is why legginess in seedlings is far more common in plants that are started on windowsills.

2. Poor Moisture

Poor moisture or inconsistent moisture can also cause your seedlings to become leggy. I struggle with this in particular – I either forget to water or water too much, overcompensating for my forgetfulness with a total deluge that just about drowns my plants.

Don’t be like me!

Instead, be consistent with your watering, and don’t let the seed starting mix dry out entirely. This will prevent your seedlings from developing strong stems and leaves.

3. Too Much Heat

There are so many benefits associated with starting your seeds on heat mats or beneath germination domes. These can cause your plants to grow quickly and can increase your germination rates, too, translating to fewer wasted seeds.

However, too much heat can also be problematic. When your seeds germinate, they will answer to the heat by shooting up tall, slender stems before the leaves can catch up. Your seedlings will be all stems and no leaves.

4. Spacing Issues

Whatever you do, don’t just errantly scatter seeds in a seed starting tray. You need proper spacing to make sure your seedlings don’t become leggy.

Cramped seedlings will, as they grow larger, compete with one another for light and nutrients.

Saving Leggy Seedlings: 6 Techniques To Try

Now that you know what causes leggy seedlings, let’s work to save the ones you already have. Here are some techniques you can try.

1. Increase Light & Temperature

First things first, let’s fix the issues you’re having with the temperature and the light.

Make sure your plants are grown under high-quality artificial grow lights. Most seedlings need about 16 hours of daylight and 8 hours of dark. Shut your grow lights off at night and you should be good to go.

If you currently have your seedling in front of a window, even a south-facing window, move them beneath an artificial grow light. The best options are LED grow lights, which don’t put off heat and are energy efficient. If you know you’ll have trouble remembering to turn the lights on and off, use a programmable timer to get yourself back on track.

You should also adjust the temperature in the room. Generally, you should aim for temperatures of around 75-80° during germination, but bump that down to 65-70° during the day and 55-60° at night.

2. Turn Fan On

This is an especially effective tip when it comes to preventing legginess in tomatoes.

Often, you can save a leggy seedling by brushing your fingers along the tops of the plants each day. Not only does it feel quite nice, but it will trick your plants into thinking there is a breeze – they will develop stronger stems as a result.

You can use a fan to mimic this, too, which will also help reduce the likelihood of damping off.

Just be aware that your plants might be more likely to dry out when you run a fan nearby.

3. Water from the Bottom Up

Another way you can salvage seedlings that have become leggy is to water from the bottom up. This will ensure that the entire seed starting medium is moist and encourages roots to spread downward.

To do this, put your seedling containers in a tray, then water the tray instead of the containers. The pots will wick up the moisture to provide the plants with exactly what they need.

4. Repot

One of my most effective tips for combatting leggy seedlings is to repot as soon as you start seeing signs of spindliness. Put your plant into a larger container and bury it up to the first set of leaves. This will help it develop stronger roots while also protecting the vulnerable stem.

5. Space Them Out

If your plants are overcrowded, it’s time to thin. You can do this by repotting or by pinching off the tops of weaker plants. Make sure each plant is spaced no less than an inch apart after they’ve developed the first set of leaves.

6. Transplant Outdoors ASAP

Last but not least, if the temperatures are appropriate and your seedlings are ready for it, go ahead and harden them off and get them outside. Often, getting them outdoors into more natural conditions (and where they have room to spread and sprawl) is the best way to combat legginess and to help your plants heal themselves.

Of course, be sure to harden off first!

Reverse the “Legginess” ASAP!

The best way to save leggy seedlings (and to prevent them from getting leggy in the first place!) is to provide them with a little more light.

Whether you’re growing your plants indoors or outside, you need to make sure they get enough sun by rotating the pots so that the leaves are facing east and west for an hour each day.

You can also use artificial lights if natural sunlight isn’t available (or not plentiful enough) in your area, but be careful not to raise the temperature of the soil too high as this will burn the tender roots.

While legginess is something that no gardener wants to see in his or her seedlings, it is, fortunately, something that can easily be reversed – as long as you take action quickly. Follow these tips and you’ll be able to save the day.